Merge bad674dd36 into 22331ed364

gradle.properties

@@ -6,3 +6,4 @@ android.enableJetifier=true
 android.defaults.buildfeatures.buildconfig=true
 android.nonTransitiveRClass=false
 android.nonFinalResIds=false
+org.gradle.java.installations.auto-download=true

uhabits-android/src/androidTest/java/org/isoron/uhabits/activities/habits/list/views/HabitCardViewTest.kt

@@ -53,7 +53,7 @@ class HabitCardViewTest : BaseViewTest() {
             .getByInterval(today.minus(300), today)
             .map { it.value }.toIntArray()
 
-        view = component.getHabitCardViewFactory().create().apply {
+        view = component.getHabitCardViewFactory().createHabitCard().apply {
             habit = habit1
             values = entries
             score = habit1.scores[today].value

uhabits-android/src/main/AndroidManifest.xml

@@ -42,6 +42,22 @@
                 android:value=".activities.habits.list.ListHabitsActivity" />
         </activity>
 
+        <activity
+            android:name=".activities.habits.list.HabitGroupPickerDialog"
+            android:exported="true">
+            <meta-data
+                android:name="android.support.PARENT_ACTIVITY"
+                android:value=".activities.habits.list.ListHabitsActivity" />
+        </activity>
+
+        <activity
+            android:name=".activities.habits.edit.EditHabitGroupActivity"
+            android:exported="true">
+            <meta-data
+                android:name="android.support.PARENT_ACTIVITY"
+                android:value=".activities.habits.list.ListHabitsActivity" />
+        </activity>
+
         <meta-data
             android:name="com.google.android.backup.api_key"
             android:value="AEdPqrEAAAAI6aeWncbnMNo8E5GWeZ44dlc5cQ7tCROwFhOtiw" />
@@ -72,6 +88,14 @@
                 android:value=".activities.habits.list.ListHabitsActivity" />
         </activity>
 
+        <activity
+            android:name=".activities.habits.show.ShowHabitGroupActivity"
+            android:label="@string/title_activity_show_habit">
+            <meta-data
+                android:name="android.support.PARENT_ACTIVITY"
+                android:value=".activities.habits.list.ListHabitsActivity" />
+        </activity>
+
         <activity
             android:name=".activities.settings.SettingsActivity"
             android:label="@string/settings">
@@ -112,6 +136,15 @@
             </intent-filter>
         </activity>
 
+        <activity
+            android:name=".widgets.activities.HabitAndGroupPickerDialog"
+            android:exported="true"
+            android:theme="@style/Theme.AppCompat.Light.Dialog">
+            <intent-filter>
+                <action android:name="android.appwidget.action.APPWIDGET_CONFIGURE" />
+            </intent-filter>
+        </activity>
+
         <activity
             android:name=".activities.about.AboutActivity"
             android:label="@string/about">

uhabits-android/src/main/java/org/isoron/uhabits/HabitsApplication.kt

@@ -79,6 +79,10 @@ class HabitsApplication : Application() {
         val habitList = component.habitList
         for (h in habitList) h.recompute()
 
+        val habitGroupList = component.habitGroupList
+        for (hgr in habitGroupList) hgr.recompute()
+        habitGroupList.attachHabitsToGroups()
+
         widgetUpdater = component.widgetUpdater.apply {
             startListening()
             scheduleStartDayWidgetUpdate()

uhabits-android/src/main/java/org/isoron/uhabits/activities/HabitsDirFinder.kt

@@ -20,6 +20,7 @@ package org.isoron.uhabits.activities
 
 import org.isoron.uhabits.AndroidDirFinder
 import org.isoron.uhabits.core.ui.screens.habits.list.ListHabitsBehavior
+import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitGroupMenuPresenter
 import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitMenuPresenter
 import java.io.File
 import javax.inject.Inject
@@ -33,3 +34,13 @@ constructor(
         return androidDirFinder.getFilesDir("CSV")!!
     }
 }
+
+class HabitGroupsDirFinder @Inject
+constructor(
+    private val androidDirFinder: AndroidDirFinder
+) : ShowHabitGroupMenuPresenter.System, ListHabitsBehavior.DirFinder {
+
+    override fun getCSVOutputDir(): File {
+        return androidDirFinder.getFilesDir("CSV")!!
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/edit/EditHabitActivity.kt

@@ -44,8 +44,9 @@ import org.isoron.uhabits.activities.common.dialogs.WeekdayPickerDialog
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateHabitCommand
 import org.isoron.uhabits.core.commands.EditHabitCommand
+import org.isoron.uhabits.core.commands.RefreshParentGroupCommand
 import org.isoron.uhabits.core.models.Frequency
-import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.HabitType
 import org.isoron.uhabits.core.models.NumericalHabitType
 import org.isoron.uhabits.core.models.PaletteColor
@@ -76,6 +77,7 @@ class EditHabitActivity : AppCompatActivity() {
 
     var habitId = -1L
     lateinit var habitType: HabitType
+    var parentGroup: HabitGroup? = null
     var unit = ""
     var color = PaletteColor(11)
     var androidColor = 0
@@ -98,10 +100,21 @@ class EditHabitActivity : AppCompatActivity() {
         binding.toolbar.applyToolbarInsets()
         setContentView(binding.root)
 
+        if (intent.hasExtra("groupId")) {
+            val groupId = intent.getLongExtra("groupId", -1L)
+            parentGroup = component.habitGroupList.getById(groupId)
+            color = parentGroup!!.color
+        }
+
         if (intent.hasExtra("habitId")) {
             binding.toolbar.title = getString(R.string.edit_habit)
-            habitId = intent.getLongExtra("habitId", -1)
+            habitId = intent.getLongExtra("habitId", -1L)
-            val habit = component.habitList.getById(habitId)!!
+            val habitList = if (parentGroup != null) {
+                parentGroup!!.habitList
+            } else {
+                component.habitList
+            }
+            val habit = habitList.getById(habitId)!!
             habitType = habit.type
             color = habit.color
             freqNum = habit.frequency.numerator
@@ -262,9 +275,14 @@ class EditHabitActivity : AppCompatActivity() {
         val component = (application as HabitsApplication).component
         val habit = component.modelFactory.buildHabit()
 
-        var original: Habit? = null
+        val habitList = if (parentGroup != null) {
-        if (habitId >= 0) {
+            parentGroup!!.habitList
-            original = component.habitList.getById(habitId)!!
+        } else {
+            component.habitList
+        }
+
+        if (habitId > 0) {
+            val original = habitList.getById(habitId)!!
             habit.copyFrom(original)
         }
 
@@ -285,21 +303,31 @@ class EditHabitActivity : AppCompatActivity() {
             habit.unit = binding.unitInput.text.trim().toString()
         }
         habit.type = habitType
+        habit.group = parentGroup
+        habit.groupId = parentGroup?.id
+        habit.groupUUID = parentGroup?.uuid
 
-        val command = if (habitId >= 0) {
+        val command = if (habitId > 0) {
             EditHabitCommand(
-                component.habitList,
+                habitList,
                 habitId,
                 habit
             )
         } else {
             CreateHabitCommand(
                 component.modelFactory,
-                component.habitList,
+                habitList,
                 habit
             )
         }
         component.commandRunner.run(command)
+
+        if (habit.groupId != null) {
+            val habitGroupList = component.habitGroupList
+            val refreshCommand = RefreshParentGroupCommand(habit, habitGroupList)
+            component.commandRunner.run(refreshCommand)
+        }
+
         finish()
     }
 

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/edit/EditHabitGroupActivity.kt

@@ -0,0 +1,232 @@
+package org.isoron.uhabits.activities.habits.edit
+
+import android.content.res.ColorStateList
+import android.graphics.Color
+import android.os.Bundle
+import android.text.Html
+import android.text.Spanned
+import android.text.format.DateFormat
+import android.view.View
+import androidx.annotation.StringRes
+import androidx.appcompat.app.AppCompatActivity
+import androidx.fragment.app.DialogFragment
+import com.android.datetimepicker.time.RadialPickerLayout
+import com.android.datetimepicker.time.TimePickerDialog
+import org.isoron.platform.gui.toInt
+import org.isoron.uhabits.HabitsApplication
+import org.isoron.uhabits.R
+import org.isoron.uhabits.activities.AndroidThemeSwitcher
+import org.isoron.uhabits.activities.common.dialogs.ColorPickerDialogFactory
+import org.isoron.uhabits.activities.common.dialogs.WeekdayPickerDialog
+import org.isoron.uhabits.core.commands.CommandRunner
+import org.isoron.uhabits.core.commands.CreateHabitGroupCommand
+import org.isoron.uhabits.core.commands.EditHabitGroupCommand
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.PaletteColor
+import org.isoron.uhabits.core.models.Reminder
+import org.isoron.uhabits.core.models.WeekdayList
+import org.isoron.uhabits.databinding.ActivityEditHabitGroupBinding
+import org.isoron.uhabits.utils.ColorUtils
+import org.isoron.uhabits.utils.dismissCurrentAndShow
+import org.isoron.uhabits.utils.formatTime
+import org.isoron.uhabits.utils.toFormattedString
+
+class EditHabitGroupActivity : AppCompatActivity() {
+
+    private lateinit var themeSwitcher: AndroidThemeSwitcher
+    private lateinit var binding: ActivityEditHabitGroupBinding
+    private lateinit var commandRunner: CommandRunner
+
+    var habitGroupId = -1L
+    var color = PaletteColor(11)
+    var androidColor = 0
+    var reminderHour = -1
+    var reminderMin = -1
+    var reminderDays: WeekdayList = WeekdayList.EVERY_DAY
+
+    override fun onCreate(state: Bundle?) {
+        super.onCreate(state)
+
+        val component = (application as HabitsApplication).component
+        themeSwitcher = AndroidThemeSwitcher(this, component.preferences)
+        themeSwitcher.apply()
+
+        binding = ActivityEditHabitGroupBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+
+        if (intent.hasExtra("habitGroupId")) {
+            binding.toolbar.title = getString(R.string.edit_habit_group)
+            habitGroupId = intent.getLongExtra("habitGroupId", -1)
+            val hgr = component.habitGroupList.getById(habitGroupId)!!
+            color = hgr.color
+            hgr.reminder?.let {
+                reminderHour = it.hour
+                reminderMin = it.minute
+                reminderDays = it.days
+            }
+            binding.nameInput.setText(hgr.name)
+            binding.questionInput.setText(hgr.question)
+            binding.notesInput.setText(hgr.description)
+        }
+
+        if (state != null) {
+            habitGroupId = state.getLong("habitGroupId")
+            color = PaletteColor(state.getInt("paletteColor"))
+            reminderHour = state.getInt("reminderHour")
+            reminderMin = state.getInt("reminderMin")
+            reminderDays = WeekdayList(state.getInt("reminderDays"))
+        }
+
+        updateColors()
+
+        setSupportActionBar(binding.toolbar)
+        supportActionBar?.setDisplayHomeAsUpEnabled(true)
+        supportActionBar?.setDisplayShowHomeEnabled(true)
+        supportActionBar?.elevation = 10.0f
+
+        val colorPickerDialogFactory = ColorPickerDialogFactory(this)
+        binding.colorButton.setOnClickListener {
+            val picker = colorPickerDialogFactory.create(color, themeSwitcher.currentTheme)
+            picker.setListener { paletteColor ->
+                this.color = paletteColor
+                updateColors()
+            }
+            picker.dismissCurrentAndShow(supportFragmentManager, "colorPicker")
+        }
+
+        populateReminder()
+        binding.reminderTimePicker.setOnClickListener {
+            val currentHour = if (reminderHour >= 0) reminderHour else 8
+            val currentMin = if (reminderMin >= 0) reminderMin else 0
+            val is24HourMode = DateFormat.is24HourFormat(this)
+            val dialog = TimePickerDialog.newInstance(
+                object : TimePickerDialog.OnTimeSetListener {
+                    override fun onTimeSet(view: RadialPickerLayout?, hourOfDay: Int, minute: Int) {
+                        reminderHour = hourOfDay
+                        reminderMin = minute
+                        populateReminder()
+                    }
+
+                    override fun onTimeCleared(view: RadialPickerLayout?) {
+                        reminderHour = -1
+                        reminderMin = -1
+                        reminderDays = WeekdayList.EVERY_DAY
+                        populateReminder()
+                    }
+                },
+                currentHour,
+                currentMin,
+                is24HourMode,
+                androidColor
+            )
+            dialog.dismissCurrentAndShow(supportFragmentManager, "timePicker")
+        }
+
+        binding.reminderDatePicker.setOnClickListener {
+            val dialog = WeekdayPickerDialog()
+
+            dialog.setListener { days: WeekdayList ->
+                reminderDays = days
+                if (reminderDays.isEmpty) reminderDays = WeekdayList.EVERY_DAY
+                populateReminder()
+            }
+            dialog.setSelectedDays(reminderDays)
+            dialog.dismissCurrentAndShow(supportFragmentManager, "dayPicker")
+        }
+
+        binding.buttonSave.setOnClickListener {
+            if (validate()) save()
+        }
+
+        for (fragment in supportFragmentManager.fragments) {
+            (fragment as DialogFragment).dismiss()
+        }
+    }
+
+    private fun save() {
+        val component = (application as HabitsApplication).component
+        val hgr = component.modelFactory.buildHabitGroup()
+
+        var original: HabitGroup? = null
+        if (habitGroupId >= 0) {
+            original = component.habitGroupList.getById(habitGroupId)!!
+            hgr.copyFrom(original)
+        }
+
+        hgr.name = binding.nameInput.text.trim().toString()
+        hgr.question = binding.questionInput.text.trim().toString()
+        hgr.description = binding.notesInput.text.trim().toString()
+        hgr.color = color
+        if (reminderHour >= 0) {
+            hgr.reminder = Reminder(reminderHour, reminderMin, reminderDays)
+        } else {
+            hgr.reminder = null
+        }
+
+        val command = if (habitGroupId >= 0) {
+            EditHabitGroupCommand(
+                component.habitGroupList,
+                habitGroupId,
+                hgr
+            )
+        } else {
+            CreateHabitGroupCommand(
+                component.modelFactory,
+                component.habitGroupList,
+                hgr
+            )
+        }
+        component.commandRunner.run(command)
+        finish()
+    }
+
+    private fun validate(): Boolean {
+        var isValid = true
+        if (binding.nameInput.text.isEmpty()) {
+            binding.nameInput.error = getFormattedValidationError(R.string.validation_cannot_be_blank)
+            isValid = false
+        }
+        return isValid
+    }
+
+    private fun populateReminder() {
+        if (reminderHour < 0) {
+            binding.reminderTimePicker.text = getString(R.string.reminder_off)
+            binding.reminderDatePicker.visibility = View.GONE
+            binding.reminderDivider.visibility = View.GONE
+        } else {
+            val time = formatTime(this, reminderHour, reminderMin)
+            binding.reminderTimePicker.text = time
+            binding.reminderDatePicker.visibility = View.VISIBLE
+            binding.reminderDivider.visibility = View.VISIBLE
+            binding.reminderDatePicker.text = reminderDays.toFormattedString(this)
+        }
+    }
+
+    private fun updateColors() {
+        androidColor = themeSwitcher.currentTheme.color(color).toInt()
+        binding.colorButton.backgroundTintList = ColorStateList.valueOf(androidColor)
+        if (!themeSwitcher.isNightMode) {
+            val darkerAndroidColor = ColorUtils.mixColors(Color.BLACK, androidColor, 0.15f)
+            window.statusBarColor = darkerAndroidColor
+            binding.toolbar.setBackgroundColor(androidColor)
+        }
+    }
+
+    private fun getFormattedValidationError(@StringRes resId: Int): Spanned {
+        val html = "<font color=#FFFFFF>${getString(resId)}</font>"
+        return Html.fromHtml(html)
+    }
+
+    override fun onSaveInstanceState(state: Bundle) {
+        super.onSaveInstanceState(state)
+        with(state) {
+            putLong("habitGroupId", habitGroupId)
+            putInt("paletteColor", color.paletteIndex)
+            putInt("androidColor", androidColor)
+            putInt("reminderHour", reminderHour)
+            putInt("reminderMin", reminderMin)
+            putInt("reminderDays", reminderDays.toInteger())
+        }
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/edit/HabitTypeDialog.kt

@@ -29,7 +29,7 @@ import org.isoron.uhabits.core.models.HabitType
 import org.isoron.uhabits.databinding.SelectHabitTypeBinding
 import org.isoron.uhabits.intents.IntentFactory
 
-class HabitTypeDialog : AppCompatDialogFragment() {
+class HabitTypeDialog(val groupId: Long? = null) : AppCompatDialogFragment() {
     override fun getTheme() = R.style.Translucent
 
     override fun onCreateView(
@@ -40,17 +40,27 @@ class HabitTypeDialog : AppCompatDialogFragment() {
         val binding = SelectHabitTypeBinding.inflate(inflater, container, false)
 
         binding.buttonYesNo.setOnClickListener {
-            val intent = IntentFactory().startEditActivity(requireActivity(), HabitType.YES_NO.value)
+            val intent = IntentFactory().startEditActivity(requireActivity(), HabitType.YES_NO.value, groupId)
             startActivity(intent)
             dismiss()
         }
 
         binding.buttonMeasurable.setOnClickListener {
-            val intent = IntentFactory().startEditActivity(requireActivity(), HabitType.NUMERICAL.value)
+            val intent = IntentFactory().startEditActivity(requireActivity(), HabitType.NUMERICAL.value, groupId)
             startActivity(intent)
             dismiss()
         }
 
+        binding.buttonHabitGroup.setOnClickListener {
+            val intent = IntentFactory().startEditGroupActivity(requireActivity())
+            startActivity(intent)
+            dismiss()
+        }
+
+        if (groupId != null) {
+            binding.buttonHabitGroup.visibility = View.GONE
+        }
+
         binding.background.setOnClickListener {
             dismiss()
         }

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/HabitGroupPickerDialog.kt

@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.activities.habits.list
+
+import android.app.Activity
+import android.os.Bundle
+import android.widget.ArrayAdapter
+import android.widget.ListView
+import android.widget.TextView
+import org.isoron.uhabits.HabitsApplication
+import org.isoron.uhabits.R
+import org.isoron.uhabits.activities.AndroidThemeSwitcher
+import org.isoron.uhabits.core.commands.AddToGroupCommand
+import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.HabitList
+import org.isoron.uhabits.inject.HabitsApplicationComponent
+
+class HabitGroupPickerDialog : Activity() {
+
+    private lateinit var habitGroupList: HabitGroupList
+    private lateinit var habitList: HabitList
+    private lateinit var selected: List<Habit>
+    private lateinit var component: HabitsApplicationComponent
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        component = (applicationContext as HabitsApplication).component
+        AndroidThemeSwitcher(this, component.preferences).apply()
+        habitList = component.habitList
+        habitGroupList = component.habitGroupList
+
+        val selectedIds = intent.getLongArrayExtra("selected")!!
+        selected = selectedIds.map { id ->
+            habitList.getById(id) ?: habitGroupList.getHabitByID(id)!!
+        }
+
+        val groupIds = ArrayList<Long>()
+        val groupNames = ArrayList<String>()
+
+        for (hgr in habitGroupList) {
+            if (hgr.isArchived) continue
+            groupIds.add(hgr.id!!)
+            groupNames.add(hgr.name)
+        }
+
+        if (groupNames.isEmpty()) {
+            setContentView(R.layout.widget_empty_activity)
+            findViewById<TextView>(R.id.message).setText(R.string.no_habit_groups)
+            return
+        }
+
+        setContentView(R.layout.widget_configure_activity)
+        val listView = findViewById<ListView>(R.id.listView)
+
+        with(listView) {
+            adapter = ArrayAdapter(
+                context,
+                android.R.layout.simple_list_item_1,
+                groupNames
+            )
+            setOnItemClickListener { parent, view, position, id ->
+                performTransfer(groupIds[position])
+            }
+        }
+    }
+    private fun performTransfer(toGroupId: Long) {
+        val hgr = habitGroupList.getById(toGroupId)!!
+        selected = selected.filter { it.groupId != hgr.id }
+        component.commandRunner.run(
+            AddToGroupCommand(habitList, hgr, selected)
+        )
+        finish()
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/ListHabitsActivity.kt

@@ -179,10 +179,20 @@ class ListHabitsActivity : AppCompatActivity(), Preferences.Listener {
             val habitId = intent.extras?.getLong("habit")
             val timestamp = intent.extras?.getLong("timestamp")
             if (habitId != null && timestamp != null) {
-                val habit = appComponent.habitList.getById(habitId)!!
+                val habit = appComponent.habitList.getById(habitId) ?: appComponent.habitGroupList.getHabitByID(habitId)!!
                 component.listHabitsBehavior.onEdit(habit, Timestamp(timestamp))
             }
         }
+        intent.getLongExtra("CLEAR_NOTIFICATION_HABIT_ID", -1).takeIf { it != -1L }?.let { id ->
+            val dismissHabit = appComponent.habitList.getById(id) ?: appComponent.habitGroupList.getHabitByID(id)
+            if (dismissHabit != null) {
+                appComponent.reminderController.onDismiss(dismissHabit)
+            } else {
+                val dismissHabitGroup = appComponent.habitGroupList.getById(id)!!
+                appComponent.reminderController.onDismiss(dismissHabitGroup)
+            }
+        }
+
         intent = null
     }
 

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/ListHabitsRootView.kt

@@ -148,7 +148,7 @@ class ListHabitsRootView @Inject constructor(
 
     private fun updateEmptyView() {
         if (listAdapter.itemCount == 0) {
-            if (listAdapter.hasNoHabit()) {
+            if (listAdapter.hasNoHabit() && listAdapter.hasNoHabitGroup()) {
                 llEmpty.showEmpty()
             } else {
                 llEmpty.showDone()

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/ListHabitsScreen.kt

@@ -41,10 +41,12 @@ import org.isoron.uhabits.core.commands.ChangeHabitColorCommand
 import org.isoron.uhabits.core.commands.Command
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateHabitCommand
+import org.isoron.uhabits.core.commands.DeleteHabitGroupsCommand
 import org.isoron.uhabits.core.commands.DeleteHabitsCommand
 import org.isoron.uhabits.core.commands.EditHabitCommand
 import org.isoron.uhabits.core.commands.UnarchiveHabitsCommand
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.PaletteColor
 import org.isoron.uhabits.core.preferences.Preferences
 import org.isoron.uhabits.core.tasks.TaskRunner
@@ -164,8 +166,8 @@ class ListHabitsScreen
         activity.startActivity(intent)
     }
 
-    override fun showSelectHabitTypeDialog() {
+    override fun showSelectHabitTypeDialog(groupId: Long?) {
-        val dialog = HabitTypeDialog()
+        val dialog = HabitTypeDialog(groupId)
         dialog.show(activity.supportFragmentManager, "habitType")
     }
 
@@ -178,6 +180,16 @@ class ListHabitsScreen
         activity.startActivity(intent)
     }
 
+    override fun showEditHabitGroupScreen(selected: List<HabitGroup>) {
+        val intent = intentFactory.startEditGroupActivity(activity, selected[0])
+        activity.startActivity(intent)
+    }
+
+    override fun showHabitGroupPickerDialog(selected: List<Habit>) {
+        val intent = intentFactory.startHabitGroupPickerActivity(activity, selected)
+        activity.startActivity(intent)
+    }
+
     override fun showFAQScreen() {
         val intent = intentFactory.viewFAQ(activity)
         activity.startActivity(intent)
@@ -188,6 +200,11 @@ class ListHabitsScreen
         activity.startActivity(intent)
     }
 
+    override fun showHabitGroupScreen(hgr: HabitGroup) {
+        val intent = intentFactory.startShowHabitGroupActivity(activity, hgr)
+        activity.startActivity(intent)
+    }
+
     fun showImportScreen() {
         val intent = intentFactory.openDocument()
         activity.startActivityForResult(intent, REQUEST_OPEN_DOCUMENT)
@@ -312,6 +329,12 @@ class ListHabitsScreen
                     command.selected.size
                 )
             }
+            is DeleteHabitGroupsCommand -> {
+                return activity.resources.getQuantityString(
+                    R.plurals.toast_habits_deleted,
+                    command.selected.size
+                )
+            }
             is EditHabitCommand -> {
                 return activity.resources.getQuantityString(R.plurals.toast_habits_changed, 1)
             }

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/ListHabitsSelectionMenu.kt

@@ -75,14 +75,18 @@ class ListHabitsSelectionMenu @Inject constructor(
         val itemColor = menu.findItem(R.id.action_color)
         val itemArchive = menu.findItem(R.id.action_archive_habit)
         val itemUnarchive = menu.findItem(R.id.action_unarchive_habit)
+        val itemRemoveFromGroup = menu.findItem(R.id.action_remove_from_group)
+        val itemAddToGroup = menu.findItem(R.id.action_add_to_group)
         val itemNotify = menu.findItem(R.id.action_notify)
 
         itemColor.isVisible = true
         itemEdit.isVisible = behavior.canEdit()
         itemArchive.isVisible = behavior.canArchive()
         itemUnarchive.isVisible = behavior.canUnarchive()
+        itemRemoveFromGroup.isVisible = behavior.areSubHabits()
+        itemAddToGroup.isVisible = behavior.areHabits()
         itemNotify.isVisible = prefs.isDeveloper
-        activeActionMode?.title = listAdapter.selected.size.toString()
+        activeActionMode?.title = (listAdapter.selectedHabits.size + listAdapter.selectedHabitGroups.size).toString()
         return true
     }
     override fun onDestroyActionMode(mode: ActionMode?) {
@@ -106,6 +110,16 @@ class ListHabitsSelectionMenu @Inject constructor(
                 return true
             }
 
+            R.id.action_remove_from_group -> {
+                behavior.onRemoveFromGroup()
+                return true
+            }
+
+            R.id.action_add_to_group -> {
+                behavior.onAddToGroup()
+                return true
+            }
+
             R.id.action_delete -> {
                 behavior.onDeleteHabits()
                 return true
@@ -117,7 +131,7 @@ class ListHabitsSelectionMenu @Inject constructor(
             }
 
             R.id.action_notify -> {
-                for (h in listAdapter.selected)
+                for (h in listAdapter.selectedHabits)
                     notificationTray.show(h, DateUtils.getToday(), 0)
                 return true
             }

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/AddButtonView.kt

@@ -0,0 +1,73 @@
+package org.isoron.uhabits.activities.habits.list.views
+
+import android.content.Context
+import android.graphics.Canvas
+import android.graphics.Paint
+import android.graphics.RectF
+import android.text.TextPaint
+import android.view.View
+import android.view.View.MeasureSpec.EXACTLY
+import org.isoron.uhabits.R
+import org.isoron.uhabits.activities.habits.list.ListHabitsActivity
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.utils.getFontAwesome
+import org.isoron.uhabits.utils.sp
+import org.isoron.uhabits.utils.sres
+import org.isoron.uhabits.utils.toMeasureSpec
+
+class AddButtonView(
+    context: Context,
+    var habitGroup: HabitGroup?
+) : View(context),
+    View.OnClickListener {
+
+    private var drawer = Drawer()
+
+    init {
+        setOnClickListener(this)
+    }
+
+    override fun onClick(v: View) {
+        (context as ListHabitsActivity).component.listHabitsMenu.behavior.onCreateHabit(habitGroup!!.id)
+    }
+
+    override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+        drawer.draw(canvas)
+    }
+
+    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
+        val height = resources.getDimensionPixelSize(R.dimen.checkmarkHeight)
+        val width = resources.getDimensionPixelSize(R.dimen.checkmarkWidth)
+        super.onMeasure(
+            width.toMeasureSpec(EXACTLY),
+            height.toMeasureSpec(EXACTLY)
+        )
+    }
+
+    private inner class Drawer {
+        private val rect = RectF()
+        private val highContrastColor = sres.getColor(R.attr.contrast80)
+
+        private val paint = TextPaint().apply {
+            typeface = getFontAwesome()
+            isAntiAlias = true
+            textAlign = Paint.Align.CENTER
+        }
+
+        fun draw(canvas: Canvas) {
+            paint.color = highContrastColor
+            val id = R.string.fa_plus
+            paint.textSize = sp(12.0f)
+            paint.strokeWidth = 0f
+            paint.style = Paint.Style.FILL
+
+            val label = resources.getString(id)
+            val em = paint.measureText("m")
+
+            rect.set(0f, 0f, width.toFloat(), height.toFloat())
+            rect.offset(0f, 0.4f * em)
+            canvas.drawText(label, rect.centerX(), rect.centerY(), paint)
+        }
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/CollapseButtonView.kt

@@ -0,0 +1,105 @@
+package org.isoron.uhabits.activities.habits.list.views
+
+import android.content.Context
+import android.graphics.Canvas
+import android.graphics.Paint
+import android.graphics.RectF
+import android.text.TextPaint
+import android.view.View
+import org.isoron.uhabits.R
+import org.isoron.uhabits.activities.habits.list.ListHabitsActivity
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.ModelObservable
+import org.isoron.uhabits.utils.getFontAwesome
+import org.isoron.uhabits.utils.sp
+import org.isoron.uhabits.utils.sres
+import org.isoron.uhabits.utils.toMeasureSpec
+
+class CollapseButtonView(
+    context: Context,
+    var habitGroup: HabitGroup?
+) : View(context),
+    View.OnClickListener,
+    ModelObservable.Listener {
+
+    private var drawer = Drawer()
+
+    var collapsed = false
+        set(value) {
+            field = value
+            drawer.rotate()
+            invalidate()
+        }
+
+    init {
+        setOnClickListener(this)
+    }
+
+    override fun onClick(v: View) {
+        collapsed = !collapsed
+        habitGroup!!.collapsed = collapsed
+        (context as ListHabitsActivity).component.listHabitsMenu.behavior.onPreferencesChanged()
+        invalidate()
+    }
+
+    override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+        drawer.draw(canvas)
+    }
+
+    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
+        val height = resources.getDimensionPixelSize(R.dimen.checkmarkHeight)
+        val width = resources.getDimensionPixelSize(R.dimen.checkmarkWidth)
+        super.onMeasure(
+            width.toMeasureSpec(MeasureSpec.EXACTLY),
+            height.toMeasureSpec(MeasureSpec.EXACTLY)
+        )
+    }
+
+    private inner class Drawer {
+        private val rect = RectF()
+        private val highContrastColor = sres.getColor(R.attr.contrast100)
+
+        private var rotationAngle = 0f
+        private var offset_y = 0.4f
+        private var offset_x = 0f
+        private val paint = TextPaint().apply {
+            typeface = getFontAwesome()
+            isAntiAlias = true
+            textAlign = Paint.Align.CENTER
+        }
+
+        fun rotate() {
+            if (collapsed) {
+                rotationAngle = 90f
+                offset_y = 0f
+                offset_x = -0.4f
+            } else {
+                rotationAngle = 0f
+                offset_y = 0.4f
+                offset_x = 0f
+            }
+        }
+
+        fun draw(canvas: Canvas) {
+            paint.color = highContrastColor
+            val id = R.string.fa_angle_down
+            paint.textSize = sp(12.0f)
+            paint.strokeWidth = 0f
+            paint.style = Paint.Style.FILL
+
+            val label = resources.getString(id)
+            val em = paint.measureText("m")
+
+            rect.set(0f, 0f, width.toFloat(), height.toFloat())
+            rect.offset(offset_x * em, offset_y * em)
+
+            canvas.save() // Save the current state of the canvas
+            canvas.rotate(rotationAngle, rect.centerX(), rect.centerY()) // Rotate the canvas
+            canvas.drawText(label, rect.centerX(), rect.centerY(), paint)
+            canvas.restore()
+        }
+    }
+
+    override fun onModelChange() {}
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitCardListAdapter.kt

@@ -18,10 +18,12 @@
  */
 package org.isoron.uhabits.activities.habits.list.views
 
+import android.annotation.SuppressLint
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.RecyclerView.Adapter
 import org.isoron.uhabits.activities.habits.list.MAX_CHECKMARK_COUNT
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.HabitMatcher
 import org.isoron.uhabits.core.models.ModelObservable
@@ -38,7 +40,7 @@ import javax.inject.Inject
  * Provides data that backs a [HabitCardListView].
  *
  *
- * The data if fetched and cached by a [HabitCardListCache]. This adapter
+ * The data is fetched and cached by a [HabitCardListCache]. This adapter
  * also holds a list of items that have been selected.
  */
 @ActivityScope
@@ -46,14 +48,16 @@ class HabitCardListAdapter @Inject constructor(
     private val cache: HabitCardListCache,
     private val preferences: Preferences,
     private val midnightTimer: MidnightTimer
-) : RecyclerView.Adapter<HabitCardViewHolder?>(),
+) : Adapter<HabitCardViewHolder?>(),
     HabitCardListCache.Listener,
     MidnightTimer.MidnightListener,
     ListHabitsMenuBehavior.Adapter,
     ListHabitsSelectionMenuBehavior.Adapter {
     val observable: ModelObservable = ModelObservable()
     private var listView: HabitCardListView? = null
-    val selected: LinkedList<Habit> = LinkedList()
+    val selectedHabits: LinkedList<Habit> = LinkedList()
+    val selectedHabitGroups: LinkedList<HabitGroup> = LinkedList()
+
     override fun atMidnight() {
         cache.refreshAllHabits()
     }
@@ -66,17 +70,27 @@ class HabitCardListAdapter @Inject constructor(
         return cache.hasNoHabit()
     }
 
+    fun hasNoHabitGroup(): Boolean {
+        return cache.hasNoHabitGroup()
+    }
+
     /**
      * Sets all items as not selected.
      */
+    @SuppressLint("NotifyDataSetChanged")
     override fun clearSelection() {
-        selected.clear()
+        selectedHabits.clear()
+        selectedHabitGroups.clear()
         notifyDataSetChanged()
         observable.notifyListeners()
     }
 
-    override fun getSelected(): List<Habit> {
+    override fun getSelectedHabits(): List<Habit> {
-        return ArrayList(selected)
+        return ArrayList(selectedHabits)
+    }
+
+    override fun getSelectedHabitGroups(): List<HabitGroup> {
+        return ArrayList(selectedHabitGroups)
     }
 
     /**
@@ -90,12 +104,20 @@ class HabitCardListAdapter @Inject constructor(
         return cache.getHabitByPosition(position)
     }
 
+    fun getHabit(position: Int): Habit? {
+        return cache.getHabitByPosition(position)
+    }
+
+    fun getHabitGroup(position: Int): HabitGroup? {
+        return cache.getHabitGroupByPosition(position)
+    }
+
     override fun getItemCount(): Int {
-        return cache.habitCount
+        return cache.itemCount
     }
 
     override fun getItemId(position: Int): Long {
-        return getItem(position)!!.id!!
+        return cache.getIdByPosition(position)!!
     }
 
     /**
@@ -104,7 +126,7 @@ class HabitCardListAdapter @Inject constructor(
      * @return true if selection is empty, false otherwise
      */
     val isSelectionEmpty: Boolean
-        get() = selected.isEmpty()
+        get() = selectedHabits.isEmpty() && selectedHabitGroups.isEmpty()
     val isSortable: Boolean
         get() = cache.primaryOrder == HabitList.Order.BY_POSITION
 
@@ -122,11 +144,18 @@ class HabitCardListAdapter @Inject constructor(
     ) {
         if (listView == null) return
         val habit = cache.getHabitByPosition(position)
-        val score = cache.getScore(habit!!.id!!)
+        if (habit != null) {
-        val checkmarks = cache.getCheckmarks(habit.id!!)
+            val score = cache.getScore(habit.id!!)
-        val notes = cache.getNotes(habit.id!!)
+            val checkmarks = cache.getCheckmarks(habit.id!!)
-        val selected = selected.contains(habit)
+            val notes = cache.getNotes(habit.id!!)
-        listView!!.bindCardView(holder, habit, score, checkmarks, notes, selected)
+            val selected = selectedHabits.contains(habit)
+            listView!!.bindCardView(holder, habit, score, checkmarks, notes, selected)
+        } else {
+            val habitGroup = cache.getHabitGroupByPosition(position)
+            val score = cache.getScore(habitGroup!!.id!!)
+            val selected = selectedHabitGroups.contains(habitGroup)
+            listView!!.bindGroupCardView(holder, habitGroup, score, selected)
+        }
     }
 
     override fun onViewAttachedToWindow(holder: HabitCardViewHolder) {
@@ -141,8 +170,22 @@ class HabitCardListAdapter @Inject constructor(
         parent: ViewGroup,
         viewType: Int
     ): HabitCardViewHolder {
-        val view = listView!!.createHabitCardView()
+        if (viewType == 0) {
-        return HabitCardViewHolder(view)
+            val view = listView!!.createHabitCardView()
+            return HabitCardViewHolder(view, null)
+        } else {
+            val view = listView!!.createHabitGroupCardView()
+            return HabitCardViewHolder(null, view)
+        }
+    }
+
+    // function to override getItemViewType and return the type of the view. The view can either be a HabitCardView or a HabitGroupCardView
+    override fun getItemViewType(position: Int): Int {
+        return if (cache.getHabitByPosition(position) != null) {
+            0
+        } else {
+            1
+        }
     }
 
     /**
@@ -193,6 +236,10 @@ class HabitCardListAdapter @Inject constructor(
         for (habit in selected) cache.remove(habit.id!!)
     }
 
+    override fun performRemoveHabitGroup(selected: List<HabitGroup>) {
+        for (hgr in selected) cache.remove(hgr.id!!)
+    }
+
     /**
      * Changes the order of habits on the adapter.
      *
@@ -249,11 +296,19 @@ class HabitCardListAdapter @Inject constructor(
      *
      * @param position position of the item to be toggled
      */
+    @SuppressLint("NotifyDataSetChanged")
     fun toggleSelection(position: Int) {
-        val h = getItem(position) ?: return
+        val h = cache.getHabitByPosition(position)
-        val k = selected.indexOf(h)
+        val hgr = cache.getHabitGroupByPosition(position)
-        if (k < 0) selected.add(h) else selected.remove(h)
+        if (h != null) {
-        notifyDataSetChanged()
+            val k = selectedHabits.indexOf(h)
+            if (k < 0) selectedHabits.add(h) else selectedHabits.remove(h)
+            notifyDataSetChanged()
+        } else if (hgr != null) {
+            val k = selectedHabitGroups.indexOf(hgr)
+            if (k < 0) selectedHabitGroups.add(hgr) else selectedHabitGroups.remove(hgr)
+            notifyDataSetChanged()
+        }
     }
 
     init {

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitCardListController.kt

@@ -50,12 +50,22 @@ class HabitCardListController @Inject constructor(
         if (from == to) return
         cancelSelection()
 
-        val habitFrom = adapter.getItem(from)
+        val habitFrom = adapter.getHabit(from)
-        val habitTo = adapter.getItem(to)
+        val habitTo = adapter.getHabit(to)
-        if (habitFrom == null || habitTo == null) return
+        if (habitFrom != null) {
+            if (habitTo != null) {
+                adapter.performReorder(from, to)
+                behavior.onReorderHabit(habitFrom, habitTo)
+            }
+            return
+        }
 
+        var hgrFrom = adapter.getHabitGroup(from)!!
+        if (hgrFrom.parent != null) hgrFrom = hgrFrom.parent!!
+        var hgrTo = adapter.getHabitGroup(to) ?: return
+        if (hgrTo.parent != null) hgrTo = hgrTo.parent!!
         adapter.performReorder(from, to)
-        behavior.onReorderHabit(habitFrom, habitTo)
+        behavior.onReorderHabitGroup(hgrFrom, hgrTo)
     }
 
     override fun onItemClick(position: Int) {
@@ -114,8 +124,15 @@ class HabitCardListController @Inject constructor(
      */
     internal inner class NormalMode : Mode {
         override fun onItemClick(position: Int) {
-            val habit = adapter.getItem(position) ?: return
+            val habit = adapter.getHabit(position)
-            behavior.onClickHabit(habit)
+            if (habit != null) {
+                behavior.onClickHabit(habit)
+            } else {
+                val hgr = adapter.getHabitGroup(position)
+                if (hgr != null) {
+                    behavior.onClickHabitGroup(hgr)
+                }
+            }
         }
 
         override fun onItemLongClick(position: Int): Boolean {

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitCardListView.kt

@@ -36,6 +36,7 @@ import dagger.Lazy
 import org.isoron.uhabits.R
 import org.isoron.uhabits.activities.common.views.BundleSavedState
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.inject.ActivityContext
 import javax.inject.Inject
 
@@ -62,8 +63,13 @@ class HabitCardListView(
         set(value) {
             field = value
             attachedHolders
-                .map { it.itemView as HabitCardView }
+                .forEach {
-                .forEach { it.dataOffset = value }
+                    if (it.itemView is HabitCardView) {
+                        (it.itemView as HabitCardView).dataOffset = value
+                    } else {
+                        (it.itemView as HabitGroupCardView).dataOffset = value
+                    }
+                }
         }
 
     private val attachedHolders = mutableListOf<HabitCardViewHolder>()
@@ -79,7 +85,11 @@ class HabitCardListView(
     }
 
     fun createHabitCardView(): HabitCardView {
-        return cardViewFactory.create()
+        return cardViewFactory.createHabitCard()
+    }
+
+    fun createHabitGroupCardView(): HabitGroupCardView {
+        return cardViewFactory.createHabitGroupCard()
     }
 
     fun bindCardView(
@@ -110,8 +120,28 @@ class HabitCardListView(
         return cardView
     }
 
+    fun bindGroupCardView(
+        holder: HabitCardViewHolder,
+        habitGroup: HabitGroup,
+        score: Double,
+        selected: Boolean
+    ): View {
+        val cardView = holder.itemView as HabitGroupCardView
+        cardView.habitGroup = habitGroup
+        cardView.isSelected = selected
+        cardView.score = score
+
+        val detector = GestureDetector(context, CardViewGestureDetector(holder))
+        cardView.setOnTouchListener { _, ev ->
+            detector.onTouchEvent(ev)
+            true
+        }
+
+        return cardView
+    }
+
     fun attachCardView(holder: HabitCardViewHolder) {
-        (holder.itemView as HabitCardView).dataOffset = dataOffset
+        (holder.itemView as? HabitCardView)?.dataOffset = dataOffset
         attachedHolders.add(holder)
     }
 

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitCardView.kt

@@ -55,7 +55,8 @@ class HabitCardViewFactory
     private val numberPanelFactory: NumberPanelViewFactory,
     private val behavior: ListHabitsBehavior
 ) {
-    fun create() = HabitCardView(context, checkmarkPanelFactory, numberPanelFactory, behavior)
+    fun createHabitCard() = HabitCardView(context, checkmarkPanelFactory, numberPanelFactory, behavior)
+    fun createHabitGroupCard() = HabitGroupCardView(context, behavior)
 }
 
 class HabitCardView(
@@ -265,6 +266,15 @@ class HabitCardView(
         }
         scoreRing.apply {
             setColor(c)
+//            if (h.isSubHabit()) {
+            val rightMargin = dp(8f).toInt()
+            val ringSize = dp(15f).toInt()
+            val leftMargin = if (h.isSubHabit() == true) dp(30f).toInt() else dp(8f).toInt()
+            layoutParams = LinearLayout.LayoutParams(ringSize, ringSize).apply {
+                setMargins(leftMargin, 0, rightMargin, 0)
+                gravity = Gravity.CENTER
+            }
+//            }
         }
         checkmarkPanel.apply {
             color = c

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitCardViewHolder.kt

@@ -21,4 +21,4 @@ package org.isoron.uhabits.activities.habits.list.views
 
 import androidx.recyclerview.widget.RecyclerView
 
-class HabitCardViewHolder(itemView: HabitCardView) : RecyclerView.ViewHolder(itemView)
+class HabitCardViewHolder(itemView1: HabitCardView?, itemView2: HabitGroupCardView?) : RecyclerView.ViewHolder(itemView1 ?: itemView2!!)

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitGroupCardView.kt

@@ -0,0 +1,172 @@
+package org.isoron.uhabits.activities.habits.list.views
+
+import android.content.Context
+import android.graphics.Typeface
+import android.graphics.text.LineBreaker.BREAK_STRATEGY_BALANCED
+import android.os.Build
+import android.os.Build.VERSION.SDK_INT
+import android.os.Handler
+import android.os.Looper
+import android.text.TextUtils
+import android.view.Gravity
+import android.view.ViewGroup.LayoutParams.MATCH_PARENT
+import android.view.ViewGroup.LayoutParams.WRAP_CONTENT
+import android.widget.FrameLayout
+import android.widget.LinearLayout
+import android.widget.TextView
+import org.isoron.platform.gui.toInt
+import org.isoron.uhabits.R
+import org.isoron.uhabits.activities.common.views.RingView
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.ModelObservable
+import org.isoron.uhabits.core.ui.screens.habits.list.ListHabitsBehavior
+import org.isoron.uhabits.inject.ActivityContext
+import org.isoron.uhabits.utils.currentTheme
+import org.isoron.uhabits.utils.dp
+import org.isoron.uhabits.utils.sres
+
+class HabitGroupCardView(
+    @ActivityContext context: Context,
+    private val behavior: ListHabitsBehavior
+) : FrameLayout(context),
+    ModelObservable.Listener {
+
+    var dataOffset = 0
+
+    var habitGroup: HabitGroup? = null
+        set(newHabitGroup) {
+            if (isAttachedToWindow) {
+                field?.observable?.removeListener(this)
+                newHabitGroup?.observable?.addListener(this)
+            }
+            field = newHabitGroup
+            if (newHabitGroup != null) copyAttributesFrom(newHabitGroup)
+            addButtonView.habitGroup = newHabitGroup
+            collapseButtonView.habitGroup = newHabitGroup
+        }
+
+    var score
+        get() = scoreRing.getPercentage().toDouble()
+        set(value) {
+            scoreRing.setPercentage(value.toFloat())
+            scoreRing.setPrecision(1.0f / 16)
+        }
+
+    var addButtonView: AddButtonView
+    var collapseButtonView: CollapseButtonView
+    private var innerFrame: LinearLayout
+    private var label: TextView
+    private var scoreRing: RingView
+
+    private var currentToggleTaskId = 0
+
+    init {
+        scoreRing = RingView(context).apply {
+            val thickness = dp(3f)
+            val margin = dp(8f).toInt()
+            val ringSize = dp(15f).toInt()
+            layoutParams = LinearLayout.LayoutParams(ringSize, ringSize).apply {
+                setMargins(margin, 0, margin, 0)
+                gravity = Gravity.CENTER
+            }
+            setThickness(thickness)
+        }
+
+        label = TextView(context).apply {
+            maxLines = 2
+            ellipsize = TextUtils.TruncateAt.END
+            layoutParams = LinearLayout.LayoutParams(0, WRAP_CONTENT, 1f)
+            if (SDK_INT >= Build.VERSION_CODES.Q) {
+                breakStrategy = BREAK_STRATEGY_BALANCED
+            }
+            setTypeface(typeface, Typeface.BOLD)
+        }
+
+        addButtonView = AddButtonView(context, habitGroup)
+        collapseButtonView = CollapseButtonView(context, habitGroup)
+
+        innerFrame = LinearLayout(context).apply {
+            gravity = Gravity.CENTER_VERTICAL
+            orientation = LinearLayout.HORIZONTAL
+            layoutParams = LinearLayout.LayoutParams(MATCH_PARENT, WRAP_CONTENT)
+            elevation = dp(1f)
+
+            addView(scoreRing)
+            addView(label)
+            addView(addButtonView)
+            addView(collapseButtonView)
+
+            setOnTouchListener { v, event ->
+                v.background.setHotspot(event.x, event.y)
+                false
+            }
+        }
+
+        clipToPadding = false
+        layoutParams = LayoutParams(MATCH_PARENT, WRAP_CONTENT)
+        val margin = dp(3f).toInt()
+        setPadding(margin, 0, margin, margin)
+        addView(innerFrame)
+    }
+
+    override fun onModelChange() {
+        Handler(Looper.getMainLooper()).post {
+            habitGroup?.let { copyAttributesFrom(it) }
+        }
+    }
+
+    override fun setSelected(isSelected: Boolean) {
+        super.setSelected(isSelected)
+        updateBackground(isSelected)
+    }
+
+    override fun onAttachedToWindow() {
+        super.onAttachedToWindow()
+        habitGroup?.observable?.addListener(this)
+    }
+
+    override fun onDetachedFromWindow() {
+        habitGroup?.observable?.removeListener(this)
+        super.onDetachedFromWindow()
+    }
+
+    private fun copyAttributesFrom(hgr: HabitGroup) {
+        fun getActiveColor(hgr: HabitGroup): Int {
+            return when (hgr.isArchived) {
+                true -> sres.getColor(R.attr.contrast60)
+                false -> currentTheme().color(hgr.color).toInt()
+            }
+        }
+
+        val c = getActiveColor(hgr)
+        label.apply {
+            text = hgr.name
+            setTextColor(c)
+        }
+        scoreRing.apply {
+            setColor(c)
+        }
+
+        collapseButtonView.collapsed = hgr.collapsed
+
+        if (collapseButtonView.collapsed) {
+            addButtonView.visibility = GONE
+        } else {
+            addButtonView.visibility = VISIBLE
+        }
+    }
+
+    private fun updateBackground(isSelected: Boolean) {
+        val background = when (isSelected) {
+            true -> R.drawable.selected_box
+            false -> R.drawable.ripple
+        }
+        innerFrame.setBackgroundResource(background)
+    }
+
+    companion object {
+        fun (() -> Unit).delay(delayInMillis: Long) {
+            Handler(Looper.getMainLooper()).postDelayed(this, delayInMillis)
+        }
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/show/ShowHabitActivity.kt

@@ -18,7 +18,6 @@
  */
 package org.isoron.uhabits.activities.habits.show
 
-import android.content.ContentUris
 import android.os.Bundle
 import android.view.HapticFeedbackConstants
 import android.view.Menu
@@ -75,8 +74,15 @@ class ShowHabitActivity : AppCompatActivity(), CommandRunner.Listener {
         super.onCreate(savedInstanceState)
 
         val appComponent = (applicationContext as HabitsApplication).component
-        val habitList = appComponent.habitList
+        val habitGroupList = appComponent.habitGroupList
-        habit = habitList.getById(ContentUris.parseId(intent.data!!))!!
+        val groupId = intent.getLongExtra("groupId", -1L)
+        val habitList = if (groupId > 0) {
+            habitGroupList.getById(groupId)!!.habitList
+        } else {
+            appComponent.habitList
+        }
+        val id = intent.getLongExtra("habitId", -1L)
+        habit = habitList.getById(id)!!
         preferences = appComponent.preferences
         commandRunner = appComponent.commandRunner
         widgetUpdater = appComponent.widgetUpdater

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/show/ShowHabitGroupActivity.kt

@@ -0,0 +1,148 @@
+package org.isoron.uhabits.activities.habits.show
+
+import android.content.ContentUris
+import android.os.Bundle
+import android.view.Menu
+import android.view.MenuItem
+import androidx.appcompat.app.AppCompatActivity
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import org.isoron.uhabits.HabitsApplication
+import org.isoron.uhabits.R
+import org.isoron.uhabits.activities.AndroidThemeSwitcher
+import org.isoron.uhabits.activities.common.dialogs.ConfirmDeleteDialog
+import org.isoron.uhabits.core.commands.Command
+import org.isoron.uhabits.core.commands.CommandRunner
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.preferences.Preferences
+import org.isoron.uhabits.core.ui.callbacks.OnConfirmedCallback
+import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitGroupMenuPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitGroupPresenter
+import org.isoron.uhabits.intents.IntentFactory
+import org.isoron.uhabits.utils.dismissCurrentAndShow
+import org.isoron.uhabits.utils.dismissCurrentDialog
+import org.isoron.uhabits.utils.showMessage
+import org.isoron.uhabits.utils.showSendFileScreen
+import org.isoron.uhabits.widgets.WidgetUpdater
+
+class ShowHabitGroupActivity : AppCompatActivity(), CommandRunner.Listener {
+
+    private lateinit var commandRunner: CommandRunner
+    private lateinit var menu: ShowHabitGroupMenu
+    private lateinit var view: ShowHabitGroupView
+    private lateinit var habitGroup: HabitGroup
+    private lateinit var preferences: Preferences
+    private lateinit var themeSwitcher: AndroidThemeSwitcher
+    private lateinit var widgetUpdater: WidgetUpdater
+
+    private val scope = CoroutineScope(Dispatchers.Main)
+    private lateinit var presenter: ShowHabitGroupPresenter
+    private val screen = Screen()
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        val appComponent = (applicationContext as HabitsApplication).component
+        val habitGroupList = appComponent.habitGroupList
+        habitGroup = habitGroupList.getById(ContentUris.parseId(intent.data!!))!!
+        preferences = appComponent.preferences
+        commandRunner = appComponent.commandRunner
+        widgetUpdater = appComponent.widgetUpdater
+
+        themeSwitcher = AndroidThemeSwitcher(this, preferences)
+        themeSwitcher.apply()
+
+        presenter = ShowHabitGroupPresenter(
+            commandRunner = commandRunner,
+            habitGroup = habitGroup,
+            preferences = preferences,
+            screen = screen
+        )
+
+        view = ShowHabitGroupView(this)
+
+        val menuPresenter = ShowHabitGroupMenuPresenter(
+            commandRunner = commandRunner,
+            habitGroup = habitGroup,
+            habitGroupList = habitGroupList,
+            screen = screen
+        )
+
+        menu = ShowHabitGroupMenu(
+            activity = this,
+            presenter = menuPresenter,
+            preferences = preferences
+        )
+
+        view.setListener(presenter)
+        setContentView(view)
+    }
+
+    override fun onCreateOptionsMenu(m: Menu): Boolean {
+        return menu.onCreateOptionsMenu(m)
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        return menu.onOptionsItemSelected(item)
+    }
+
+    override fun onResume() {
+        super.onResume()
+        commandRunner.addListener(this)
+        screen.refresh()
+    }
+
+    override fun onPause() {
+        dismissCurrentDialog()
+        commandRunner.removeListener(this)
+        super.onPause()
+    }
+
+    override fun onCommandFinished(command: Command) {
+        screen.refresh()
+    }
+
+    inner class Screen : ShowHabitGroupMenuPresenter.Screen, ShowHabitGroupPresenter.Screen {
+        override fun updateWidgets() {
+            widgetUpdater.updateWidgets()
+        }
+
+        override fun refresh() {
+            scope.launch {
+                view.setState(
+                    ShowHabitGroupPresenter.buildState(
+                        habitGroup = habitGroup,
+                        preferences = preferences,
+                        theme = themeSwitcher.currentTheme
+                    )
+                )
+            }
+        }
+
+        override fun showEditHabitGroupScreen(habitGroup: HabitGroup) {
+            startActivity(IntentFactory().startEditGroupActivity(this@ShowHabitGroupActivity, habitGroup))
+        }
+
+        override fun showMessage(m: ShowHabitGroupMenuPresenter.Message?) {
+            when (m) {
+                ShowHabitGroupMenuPresenter.Message.COULD_NOT_EXPORT -> {
+                    showMessage(resources.getString(R.string.could_not_export))
+                }
+                else -> {}
+            }
+        }
+
+        override fun showSendFileScreen(filename: String) {
+            this@ShowHabitGroupActivity.showSendFileScreen(filename)
+        }
+
+        override fun showDeleteConfirmationScreen(callback: OnConfirmedCallback) {
+            ConfirmDeleteDialog(this@ShowHabitGroupActivity, callback, 1).dismissCurrentAndShow()
+        }
+
+        override fun close() {
+            this@ShowHabitGroupActivity.finish()
+        }
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/show/ShowHabitGroupMenu.kt

@@ -0,0 +1,32 @@
+package org.isoron.uhabits.activities.habits.show
+
+import android.view.Menu
+import android.view.MenuItem
+import org.isoron.uhabits.R
+import org.isoron.uhabits.core.preferences.Preferences
+import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitGroupMenuPresenter
+
+class ShowHabitGroupMenu(
+    val activity: ShowHabitGroupActivity,
+    val presenter: ShowHabitGroupMenuPresenter,
+    val preferences: Preferences
+) {
+    fun onCreateOptionsMenu(menu: Menu): Boolean {
+        activity.menuInflater.inflate(R.menu.show_habit_group, menu)
+        return true
+    }
+
+    fun onOptionsItemSelected(item: MenuItem): Boolean {
+        when (item.itemId) {
+            R.id.action_edit_habit_group -> {
+                presenter.onEditHabitGroup()
+                return true
+            }
+            R.id.action_delete -> {
+                presenter.onDeleteHabitGroup()
+                return true
+            }
+        }
+        return false
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/show/ShowHabitGroupView.kt

@@ -0,0 +1,56 @@
+package org.isoron.uhabits.activities.habits.show
+
+import android.content.Context
+import android.view.LayoutInflater
+import android.widget.FrameLayout
+import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitGroupPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.ShowHabitGroupState
+import org.isoron.uhabits.databinding.ShowHabitGroupBinding
+import org.isoron.uhabits.utils.setupToolbar
+
+class ShowHabitGroupView(context: Context) : FrameLayout(context) {
+    private val binding = ShowHabitGroupBinding.inflate(LayoutInflater.from(context))
+
+    init {
+        addView(binding.root)
+    }
+
+    fun setState(data: ShowHabitGroupState) {
+        setupToolbar(
+            binding.toolbar,
+            title = data.title,
+            color = data.color,
+            theme = data.theme
+        )
+        binding.subtitleCard.setState(data.subtitle)
+        binding.overviewCard.setState(data.overview)
+        binding.notesCard.setState(data.notes)
+        binding.targetCard.setState(data.target)
+        binding.streakCard.setState(data.streaks)
+        binding.scoreCard.setState(data.scores)
+        binding.barCard.setState(data.bar)
+        binding.frequencyCard.setState(data.frequency)
+        if (!data.isBoolean) {
+            binding.streakCard.visibility = GONE
+            if (!data.isNumerical) {
+                binding.barCard.visibility = GONE
+            }
+        }
+        if (!data.isNumerical) {
+            binding.targetCard.visibility = GONE
+        }
+        if (data.isEmpty) {
+            binding.targetCard.visibility = GONE
+            binding.barCard.visibility = GONE
+            binding.streakCard.visibility = GONE
+            binding.overviewCard.visibility = GONE
+            binding.scoreCard.visibility = GONE
+            binding.frequencyCard.visibility = GONE
+            binding.noSubHabitsCard.visibility = VISIBLE
+        }
+    }
+
+    fun setListener(presenter: ShowHabitGroupPresenter) {
+        binding.scoreCard.setListener(presenter.scoreCardPresenter)
+    }
+}

uhabits-android/src/main/java/org/isoron/uhabits/inject/HabitsApplicationComponent.kt

@@ -24,6 +24,7 @@ import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.io.GenericImporter
 import org.isoron.uhabits.core.io.Logging
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.ModelFactory
 import org.isoron.uhabits.core.preferences.Preferences
@@ -50,6 +51,7 @@ interface HabitsApplicationComponent {
     val genericImporter: GenericImporter
     val habitCardListCache: HabitCardListCache
     val habitList: HabitList
+    val habitGroupList: HabitGroupList
     val intentFactory: IntentFactory
     val intentParser: IntentParser
     val logging: Logging

uhabits-android/src/main/java/org/isoron/uhabits/inject/HabitsModule.kt

@@ -26,9 +26,11 @@ import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.database.Database
 import org.isoron.uhabits.core.database.DatabaseOpener
 import org.isoron.uhabits.core.io.Logging
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.ModelFactory
 import org.isoron.uhabits.core.models.sqlite.SQLModelFactory
+import org.isoron.uhabits.core.models.sqlite.SQLiteHabitGroupList
 import org.isoron.uhabits.core.models.sqlite.SQLiteHabitList
 import org.isoron.uhabits.core.preferences.Preferences
 import org.isoron.uhabits.core.preferences.WidgetPreferences
@@ -61,9 +63,10 @@ class HabitsModule(dbFile: File) {
         sys: IntentScheduler,
         commandRunner: CommandRunner,
         habitList: HabitList,
+        habitGroupList: HabitGroupList,
         widgetPreferences: WidgetPreferences
     ): ReminderScheduler {
-        return ReminderScheduler(commandRunner, habitList, sys, widgetPreferences)
+        return ReminderScheduler(commandRunner, habitList, habitGroupList, sys, widgetPreferences)
     }
 
     @Provides
@@ -97,6 +100,12 @@ class HabitsModule(dbFile: File) {
         return list
     }
 
+    @Provides
+    @AppScope
+    fun getHabitGroupList(list: SQLiteHabitGroupList): HabitGroupList {
+        return list
+    }
+
     @Provides
     @AppScope
     fun getDatabaseOpener(opener: AndroidDatabaseOpener): DatabaseOpener {

uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentFactory.kt

@@ -25,10 +25,14 @@ import android.net.Uri
 import org.isoron.uhabits.R
 import org.isoron.uhabits.activities.about.AboutActivity
 import org.isoron.uhabits.activities.habits.edit.EditHabitActivity
+import org.isoron.uhabits.activities.habits.edit.EditHabitGroupActivity
+import org.isoron.uhabits.activities.habits.list.HabitGroupPickerDialog
 import org.isoron.uhabits.activities.habits.show.ShowHabitActivity
+import org.isoron.uhabits.activities.habits.show.ShowHabitGroupActivity
 import org.isoron.uhabits.activities.intro.IntroActivity
 import org.isoron.uhabits.activities.settings.SettingsActivity
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import javax.inject.Inject
 
 class IntentFactory
@@ -60,9 +64,16 @@ class IntentFactory
     fun startSettingsActivity(context: Context) =
         Intent(context, SettingsActivity::class.java)
 
-    fun startShowHabitActivity(context: Context, habit: Habit) =
+    fun startShowHabitActivity(context: Context, habit: Habit): Intent {
-        Intent(context, ShowHabitActivity::class.java).apply {
+        val intent = Intent(context, ShowHabitActivity::class.java)
-            data = Uri.parse(habit.uriString)
+        intent.putExtra("habitId", habit.id)
+        intent.putExtra("groupId", habit.groupId)
+        return intent
+    }
+
+    fun startShowHabitGroupActivity(context: Context, habitGroup: HabitGroup) =
+        Intent(context, ShowHabitGroupActivity::class.java).apply {
+            data = Uri.parse(habitGroup.uriString)
         }
 
     fun viewFAQ(context: Context) =
@@ -92,12 +103,33 @@ class IntentFactory
         val intent = startEditActivity(context)
         intent.putExtra("habitId", habit.id)
         intent.putExtra("habitType", habit.type)
+        if (habit.groupId != null) intent.putExtra("groupId", habit.groupId)
         return intent
     }
 
-    fun startEditActivity(context: Context, habitType: Int): Intent {
+    fun startEditActivity(context: Context, habitType: Int, groupId: Long?): Intent {
         val intent = startEditActivity(context)
         intent.putExtra("habitType", habitType)
+        if (groupId != null) {
+            intent.putExtra("groupId", groupId)
+        }
+        return intent
+    }
+
+    fun startEditGroupActivity(context: Context): Intent {
+        return Intent(context, EditHabitGroupActivity::class.java)
+    }
+
+    fun startEditGroupActivity(context: Context, habitGroup: HabitGroup): Intent {
+        val intent = startEditGroupActivity(context)
+        intent.putExtra("habitGroupId", habitGroup.id)
+        return intent
+    }
+
+    fun startHabitGroupPickerActivity(context: Context, selected: List<Habit>): Intent {
+        val intent = Intent(context, HabitGroupPickerDialog::class.java)
+        val ids = selected.map { it.id!! }.toLongArray()
+        intent.putExtra("selected", ids)
         return intent
     }
 }

uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentParser.kt

@@ -24,6 +24,7 @@ import android.content.Intent
 import android.net.Uri
 import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.utils.DateUtils
@@ -31,7 +32,10 @@ import javax.inject.Inject
 
 @AppScope
 class IntentParser
-@Inject constructor(private val habits: HabitList) {
+@Inject constructor(
+    private val habits: HabitList,
+    private val habitGroups: HabitGroupList
+) {
 
     fun parseCheckmarkIntent(intent: Intent): CheckmarkIntentData {
         val uri = intent.data ?: throw IllegalArgumentException("uri is null")
@@ -45,6 +49,7 @@ class IntentParser
 
     private fun parseHabit(uri: Uri): Habit {
         return habits.getById(parseId(uri))
+            ?: habitGroups.getHabitByID(parseId(uri))
             ?: throw IllegalArgumentException("habit not found")
     }
 

uhabits-android/src/main/java/org/isoron/uhabits/intents/IntentScheduler.kt

@@ -29,6 +29,7 @@ import android.os.Build
 import android.util.Log
 import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.reminders.ReminderScheduler.SchedulerResult
 import org.isoron.uhabits.core.reminders.ReminderScheduler.SystemScheduler
 import org.isoron.uhabits.core.utils.DateFormats
@@ -75,6 +76,16 @@ class IntentScheduler
         return schedule(reminderTime, intent, RTC_WAKEUP)
     }
 
+    override fun scheduleShowReminder(
+        reminderTime: Long,
+        habitGroup: HabitGroup,
+        timestamp: Long
+    ): SchedulerResult {
+        val intent = pendingIntents.showReminder(habitGroup, reminderTime, timestamp)
+        logReminderScheduled(habitGroup, reminderTime)
+        return schedule(reminderTime, intent, RTC_WAKEUP)
+    }
+
     override fun scheduleWidgetUpdate(updateTime: Long): SchedulerResult {
         val intent = pendingIntents.updateWidgets()
         return schedule(updateTime, intent, RTC)
@@ -94,4 +105,15 @@ class IntentScheduler
             String.format("Setting alarm (%s): %s", time, name)
         )
     }
+
+    private fun logReminderScheduled(habitGroup: HabitGroup, reminderTime: Long) {
+        val min = min(5, habitGroup.name.length)
+        val name = habitGroup.name.substring(0, min)
+        val df = DateFormats.getBackupDateFormat()
+        val time = df.format(Date(reminderTime))
+        Log.i(
+            "ReminderHelper",
+            String.format("Setting alarm (%s): %s", time, name)
+        )
+    }
 }

uhabits-android/src/main/java/org/isoron/uhabits/intents/PendingIntentFactory.kt

@@ -31,8 +31,10 @@ import android.net.Uri
 import android.os.Build
 import org.isoron.uhabits.activities.habits.list.ListHabitsActivity
 import org.isoron.uhabits.activities.habits.show.ShowHabitActivity
+import org.isoron.uhabits.activities.habits.show.ShowHabitGroupActivity
 import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.inject.AppContext
 import org.isoron.uhabits.receivers.ReminderReceiver
@@ -69,6 +71,17 @@ class PendingIntentFactory
             FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
+    fun dismissNotification(habitGroup: HabitGroup): PendingIntent =
+        getBroadcast(
+            context,
+            0,
+            Intent(context, ReminderReceiver::class.java).apply {
+                action = WidgetReceiver.ACTION_DISMISS_REMINDER
+                data = Uri.parse(habitGroup.uriString)
+            },
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
+        )
+
     fun removeRepetition(habit: Habit, timestamp: Timestamp?): PendingIntent =
         getBroadcast(
             context,
@@ -92,6 +105,17 @@ class PendingIntentFactory
             )
             .getPendingIntent(0, FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT)!!
 
+    fun showHabitGroup(habitGroup: HabitGroup): PendingIntent =
+        androidx.core.app.TaskStackBuilder
+            .create(context)
+            .addNextIntentWithParentStack(
+                intentFactory.startShowHabitGroupActivity(
+                    context,
+                    habitGroup
+                )
+            )
+            .getPendingIntent(0, FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT)!!
+
     fun showHabitTemplate(): PendingIntent {
         return getActivity(
             context,
@@ -101,6 +125,15 @@ class PendingIntentFactory
         )
     }
 
+    fun showHabitGroupTemplate(): PendingIntent {
+        return getActivity(
+            context,
+            0,
+            Intent(context, ShowHabitGroupActivity::class.java),
+            getIntentTemplateFlags()
+        )
+    }
+
     fun showHabitFillIn(habit: Habit) =
         Intent().apply {
             data = Uri.parse(habit.uriString)
@@ -123,6 +156,23 @@ class PendingIntentFactory
             FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
+    fun showReminder(
+        habitGroup: HabitGroup,
+        reminderTime: Long?,
+        timestamp: Long
+    ): PendingIntent =
+        getBroadcast(
+            context,
+            (habitGroup.id!! % Integer.MAX_VALUE).toInt() + 1,
+            Intent(context, ReminderReceiver::class.java).apply {
+                action = ReminderReceiver.ACTION_SHOW_REMINDER
+                data = Uri.parse(habitGroup.uriString)
+                putExtra("timestamp", timestamp)
+                putExtra("reminderTime", reminderTime)
+            },
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
+        )
+
     fun snoozeNotification(habit: Habit): PendingIntent =
         getBroadcast(
             context,
@@ -134,6 +184,17 @@ class PendingIntentFactory
             FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
         )
 
+    fun snoozeNotification(habitGroup: HabitGroup): PendingIntent =
+        getBroadcast(
+            context,
+            0,
+            Intent(context, ReminderReceiver::class.java).apply {
+                data = Uri.parse(habitGroup.uriString)
+                action = ReminderReceiver.ACTION_SNOOZE_REMINDER
+            },
+            FLAG_IMMUTABLE or FLAG_UPDATE_CURRENT
+        )
+
     fun toggleCheckmark(habit: Habit, timestamp: Long?): PendingIntent =
         getBroadcast(
             context,
@@ -185,6 +246,26 @@ class PendingIntentFactory
         putExtra("timestamp", timestamp.unixTime)
     }
 
+    fun showHabitList(): PendingIntent {
+        return getActivity(
+            context,
+            1,
+            Intent(context, ListHabitsActivity::class.java),
+            getIntentTemplateFlags()
+        )
+    }
+
+    fun showHabitListWithNotificationClear(id: Long): PendingIntent {
+        return getActivity(
+            context,
+            0,
+            Intent(context, ListHabitsActivity::class.java).apply {
+                putExtra("CLEAR_NOTIFICATION_HABIT_ID", id)
+            },
+            getIntentTemplateFlags()
+        )
+    }
+
     private fun getIntentTemplateFlags(): Int {
         var flags = 0
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {

uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt

@@ -35,6 +35,7 @@ import androidx.core.app.NotificationManagerCompat
 import org.isoron.uhabits.R
 import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.preferences.Preferences
 import org.isoron.uhabits.core.ui.NotificationTray
@@ -90,6 +91,34 @@ class AndroidNotificationTray
         active.add(notificationId)
     }
 
+    override fun showNotification(
+        habitGroup: HabitGroup,
+        notificationId: Int,
+        timestamp: Timestamp,
+        reminderTime: Long
+    ) {
+        val notificationManager = NotificationManagerCompat.from(context)
+        val notification = buildNotification(habitGroup, reminderTime, timestamp)
+        createAndroidNotificationChannel(context)
+        try {
+            notificationManager.notify(notificationId, notification)
+        } catch (e: RuntimeException) {
+            // Some Xiaomi phones produce a RuntimeException if custom notification sounds are used.
+            Log.i(
+                "AndroidNotificationTray",
+                "Failed to show notification. Retrying without sound."
+            )
+            val n = buildNotification(
+                habitGroup,
+                reminderTime,
+                timestamp,
+                disableSound = true
+            )
+            notificationManager.notify(notificationId, n)
+        }
+        active.add(notificationId)
+    }
+
     fun buildNotification(
         habit: Habit,
         reminderTime: Long,
@@ -163,6 +192,58 @@ class AndroidNotificationTray
         return builder.build()
     }
 
+    fun buildNotification(
+        habitGroup: HabitGroup,
+        reminderTime: Long,
+        timestamp: Timestamp,
+        disableSound: Boolean = false
+    ): Notification {
+        val enterAction = Action(
+            R.drawable.ic_action_check,
+            context.getString(R.string.enter),
+            pendingIntents.showHabitListWithNotificationClear(habitGroup.id!!)
+        )
+
+        val wearableBg = decodeResource(context.resources, R.drawable.stripe)
+
+        // Even though the set of actions is the same on the phone and
+        // on the watch, Pebble requires us to add them to the
+        // WearableExtender.
+        val wearableExtender = WearableExtender().setBackground(wearableBg)
+
+        val defaultText = context.getString(R.string.default_reminder_question)
+        val builder = Builder(context, REMINDERS_CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_notification)
+            .setContentTitle(habitGroup.name)
+            .setContentText(if (habitGroup.question.isBlank()) defaultText else habitGroup.question)
+            .setContentIntent(pendingIntents.showHabitGroup(habitGroup))
+            .setDeleteIntent(pendingIntents.dismissNotification(habitGroup))
+            .setSound(null)
+            .setWhen(reminderTime)
+            .setShowWhen(true)
+            .setOngoing(preferences.shouldMakeNotificationsSticky())
+
+        wearableExtender.addAction(enterAction)
+        builder.addAction(enterAction)
+
+        if (!disableSound) {
+            builder.setSound(ringtoneManager.getURI())
+        }
+
+        if (SDK_INT < Build.VERSION_CODES.S) {
+            val snoozeAction = Action(
+                R.drawable.ic_action_snooze,
+                context.getString(R.string.snooze),
+                pendingIntents.snoozeNotification(habitGroup)
+            )
+            wearableExtender.addAction(snoozeAction)
+            builder.addAction(snoozeAction)
+        }
+
+        builder.extend(wearableExtender)
+        return builder.build()
+    }
+
     companion object {
         private const val REMINDERS_CHANNEL_ID = "REMINDERS"
         fun createAndroidNotificationChannel(context: Context) {

uhabits-android/src/main/java/org/isoron/uhabits/notifications/SnoozeDelayPickerActivity.kt

@@ -33,6 +33,7 @@ import org.isoron.uhabits.HabitsApplication
 import org.isoron.uhabits.R
 import org.isoron.uhabits.activities.AndroidThemeSwitcher
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.ui.views.DarkTheme
 import org.isoron.uhabits.core.ui.views.LightTheme
 import org.isoron.uhabits.receivers.ReminderController
@@ -41,6 +42,7 @@ import java.util.Calendar
 
 class SnoozeDelayPickerActivity : FragmentActivity(), OnItemClickListener {
     private var habit: Habit? = null
+    private var habitGroup: HabitGroup? = null
     private var reminderController: ReminderController? = null
     private var dialog: AlertDialog? = null
     private var androidColor: Int = 0
@@ -58,10 +60,13 @@ class SnoozeDelayPickerActivity : FragmentActivity(), OnItemClickListener {
         if (data == null) {
             finish()
         } else {
-            habit = appComponent.habitList.getById(ContentUris.parseId(data))
+            val id = ContentUris.parseId(data)
+            habit = appComponent.habitList.getById(id) ?: appComponent.habitGroupList.getHabitByID(id)
+            habitGroup = appComponent.habitGroupList.getById(id)
         }
-        if (habit == null) finish()
+        if (habit == null && habitGroup == null) finish()
-        androidColor = themeSwitcher.currentTheme.color(habit!!.color).toInt()
+        val color = habit?.color ?: habitGroup!!.color
+        androidColor = themeSwitcher.currentTheme.color(color).toInt()
         reminderController = appComponent.reminderController
         dialog = AlertDialog.Builder(this)
             .setTitle(R.string.select_snooze_delay)
@@ -87,7 +92,11 @@ class SnoozeDelayPickerActivity : FragmentActivity(), OnItemClickListener {
         val calendar = Calendar.getInstance()
         val dialog = TimePickerDialog.newInstance(
             { view: RadialPickerLayout?, hour: Int, minute: Int ->
-                reminderController!!.onSnoozeTimePicked(habit, hour, minute)
+                if (habit != null) {
+                    reminderController!!.onSnoozeTimePicked(habit, hour, minute)
+                } else {
+                    reminderController!!.onSnoozeTimePicked(habitGroup, hour, minute)
+                }
                 finish()
             },
             calendar[Calendar.HOUR_OF_DAY],
@@ -101,7 +110,11 @@ class SnoozeDelayPickerActivity : FragmentActivity(), OnItemClickListener {
     override fun onItemClick(parent: AdapterView<*>?, view: View, position: Int, id: Long) {
         val snoozeValues = resources.getIntArray(R.array.snooze_picker_values)
         if (snoozeValues[position] >= 0) {
-            reminderController!!.onSnoozeDelayPicked(habit!!, snoozeValues[position])
+            if (habit != null) {
+                reminderController!!.onSnoozeDelayPicked(habit!!, snoozeValues[position])
+            } else {
+                reminderController!!.onSnoozeDelayPicked(habitGroup!!, snoozeValues[position])
+            }
             finish()
         } else {
             showTimePicker()

uhabits-android/src/main/java/org/isoron/uhabits/receivers/ReminderController.kt

@@ -23,6 +23,7 @@ import android.content.Intent
 import android.net.Uri
 import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.preferences.Preferences
 import org.isoron.uhabits.core.reminders.ReminderScheduler
@@ -50,21 +51,45 @@ class ReminderController @Inject constructor(
         reminderScheduler.scheduleAll()
     }
 
+    fun onShowReminder(
+        habitGroup: HabitGroup,
+        timestamp: Timestamp,
+        reminderTime: Long
+    ) {
+        notificationTray.show(habitGroup, timestamp, reminderTime)
+        reminderScheduler.scheduleAll()
+    }
+
     fun onSnoozePressed(habit: Habit, context: Context) {
         showSnoozeDelayPicker(habit, context)
     }
 
+    fun onSnoozePressed(habitGroup: HabitGroup, context: Context) {
+        showSnoozeDelayPicker(habitGroup, context)
+    }
+
     fun onSnoozeDelayPicked(habit: Habit, delayInMinutes: Int) {
         reminderScheduler.snoozeReminder(habit, delayInMinutes.toLong())
         notificationTray.cancel(habit)
     }
 
+    fun onSnoozeDelayPicked(habitGroup: HabitGroup, delayInMinutes: Int) {
+        reminderScheduler.snoozeReminder(habitGroup, delayInMinutes.toLong())
+        notificationTray.cancel(habitGroup)
+    }
+
     fun onSnoozeTimePicked(habit: Habit?, hour: Int, minute: Int) {
         val time: Long = getUpcomingTimeInMillis(hour, minute)
         reminderScheduler.scheduleAtTime(habit!!, time)
         notificationTray.cancel(habit)
     }
 
+    fun onSnoozeTimePicked(habitGroup: HabitGroup?, hour: Int, minute: Int) {
+        val time: Long = getUpcomingTimeInMillis(hour, minute)
+        reminderScheduler.scheduleAtTime(habitGroup!!, time)
+        notificationTray.cancel(habitGroup)
+    }
+
     fun onDismiss(habit: Habit) {
         if (preferences.shouldMakeNotificationsSticky()) {
             // This is a workaround to keep sticky notifications non-dismissible in Android 14+.
@@ -75,6 +100,16 @@ class ReminderController @Inject constructor(
         }
     }
 
+    fun onDismiss(habitGroup: HabitGroup) {
+        if (preferences.shouldMakeNotificationsSticky()) {
+            // This is a workaround to keep sticky notifications non-dismissible in Android 14+.
+            // If the notification is dismissed, we immediately reshow it.
+            notificationTray.reshow(habitGroup)
+        } else {
+            notificationTray.cancel(habitGroup)
+        }
+    }
+
     private fun showSnoozeDelayPicker(habit: Habit, context: Context) {
         context.sendBroadcast(Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS))
         val intent = Intent(context, SnoozeDelayPickerActivity::class.java)
@@ -82,4 +117,12 @@ class ReminderController @Inject constructor(
         intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
         context.startActivity(intent)
     }
+
+    private fun showSnoozeDelayPicker(habitGroup: HabitGroup, context: Context) {
+        context.sendBroadcast(Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS))
+        val intent = Intent(context, SnoozeDelayPickerActivity::class.java)
+        intent.data = Uri.parse(habitGroup.uriString)
+        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+        context.startActivity(intent)
+    }
 }

uhabits-android/src/main/java/org/isoron/uhabits/receivers/ReminderReceiver.kt

@@ -27,6 +27,7 @@ import android.os.Build.VERSION.SDK_INT
 import android.util.Log
 import org.isoron.uhabits.HabitsApplication
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.utils.DateUtils.Companion.getStartOfTodayWithOffset
 
@@ -44,52 +45,81 @@ class ReminderReceiver : BroadcastReceiver() {
         val app = context.applicationContext as HabitsApplication
         val appComponent = app.component
         val habits = appComponent.habitList
+        val habitGroups = appComponent.habitGroupList
         val reminderController = appComponent.reminderController
         Log.i(TAG, String.format("Received intent: %s", intent.toString()))
         var habit: Habit? = null
+        var habitGroup: HabitGroup? = null
+        var id: Long? = null
+        var type: String? = null
         val today: Long = getStartOfTodayWithOffset()
         val data = intent.data
-        if (data != null) habit = habits.getById(ContentUris.parseId(data))
+        if (data != null) {
+            type = data.pathSegments[0]
+            id = ContentUris.parseId(data)
+            when (type) {
+                "habit" -> habit = habits.getById(id) ?: habitGroups.getHabitByID(id)
+                "habitgroup" -> habitGroup = habitGroups.getById(id)
+            }
+        }
         val timestamp = intent.getLongExtra("timestamp", today)
         val reminderTime = intent.getLongExtra("reminderTime", today)
         try {
             when (intent.action) {
                 ACTION_SHOW_REMINDER -> {
-                    if (habit == null) return
+                    if (id == null) return
                     Log.d(
                         "ReminderReceiver",
                         String.format(
-                            "onShowReminder habit=%d timestamp=%d reminderTime=%d",
+                            "onShowReminder %s=%d timestamp=%d reminderTime=%d",
-                            habit.id,
+                            type,
+                            id,
                             timestamp,
                             reminderTime
                         )
                     )
-                    reminderController.onShowReminder(
+                    if (habit != null) {
-                        habit,
+                        reminderController.onShowReminder(
-                        Timestamp(timestamp),
+                            habit,
-                        reminderTime
+                            Timestamp(timestamp),
-                    )
+                            reminderTime
+                        )
+                    } else {
+                        reminderController.onShowReminder(
+                            habitGroup!!,
+                            Timestamp(timestamp),
+                            reminderTime
+                        )
+                    }
                 }
                 ACTION_DISMISS_REMINDER -> {
-                    if (habit == null) return
+                    if (id == null) return
-                    Log.d("ReminderReceiver", String.format("onDismiss habit=%d", habit.id))
+                    Log.d("ReminderReceiver", String.format("onDismiss %s=%d", type, id))
-                    reminderController.onDismiss(habit)
+                    if (habit != null) {
+                        reminderController.onDismiss(habit)
+                    } else {
+                        reminderController.onDismiss(habitGroup!!)
+                    }
                 }
                 ACTION_SNOOZE_REMINDER -> {
-                    if (habit == null) return
+                    if (id == null) return
                     if (SDK_INT < Build.VERSION_CODES.S) {
                         Log.d(
                             "ReminderReceiver",
-                            String.format("onSnoozePressed habit=%d", habit.id)
+                            String.format("onSnoozePressed %s=%d", type, id)
                         )
-                        reminderController.onSnoozePressed(habit, context)
+                        if (habit != null) {
+                            reminderController.onSnoozePressed(habit, context)
+                        } else {
+                            reminderController.onSnoozePressed(habitGroup!!, context)
+                        }
                     } else {
                         Log.w(
                             "ReminderReceiver",
                             String.format(
-                                "onSnoozePressed habit=%d, should be deactivated in recent versions.",
+                                "onSnoozePressed %s=%d, should be deactivated in recent versions.",
-                                habit.id
+                                type,
+                                id
                             )
                         )
                     }

uhabits-android/src/main/java/org/isoron/uhabits/widgets/BaseWidgetProvider.kt

@@ -27,15 +27,17 @@ import android.widget.RemoteViews
 import org.isoron.uhabits.HabitsApplication
 import org.isoron.uhabits.R
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.HabitNotFoundException
 import org.isoron.uhabits.core.preferences.Preferences
 import org.isoron.uhabits.core.preferences.WidgetPreferences
 import org.isoron.uhabits.utils.InterfaceUtils.dpToPixels
-import java.util.ArrayList
 
 abstract class BaseWidgetProvider : AppWidgetProvider() {
     private lateinit var habits: HabitList
+    private lateinit var habitGroups: HabitGroupList
     lateinit var preferences: Preferences
         private set
     private lateinit var widgetPrefs: WidgetPreferences
@@ -112,12 +114,26 @@ abstract class BaseWidgetProvider : AppWidgetProvider() {
         val selectedIds = widgetPrefs.getHabitIdsFromWidgetId(widgetId)
         val selectedHabits = ArrayList<Habit>(selectedIds.size)
         for (id in selectedIds) {
-            val h = habits.getById(id) ?: throw HabitNotFoundException()
+            val h = habits.getById(id) ?: habitGroups.getHabitByID(id)
-            selectedHabits.add(h)
+            if (h != null) {
+                selectedHabits.add(h)
+            }
         }
         return selectedHabits
     }
 
+    protected fun getHabitGroupsFromWidgetId(widgetId: Int): List<HabitGroup> {
+        val selectedIds = widgetPrefs.getHabitIdsFromWidgetId(widgetId)
+        val selectedHabitGroups = ArrayList<HabitGroup>(selectedIds.size)
+        for (id in selectedIds) {
+            val hgr = habitGroups.getById(id)
+            if (hgr != null) {
+                selectedHabitGroups.add(hgr)
+            }
+        }
+        return selectedHabitGroups
+    }
+
     protected abstract fun getWidgetFromId(
         context: Context,
         id: Int
@@ -159,6 +175,7 @@ abstract class BaseWidgetProvider : AppWidgetProvider() {
     private fun updateDependencies(context: Context) {
         val app = context.applicationContext as HabitsApplication
         habits = app.component.habitList
+        habitGroups = app.component.habitGroupList
         preferences = app.component.preferences
         widgetPrefs = app.component.widgetPreferences
     }

uhabits-android/src/main/java/org/isoron/uhabits/widgets/FrequencyWidget.kt

@@ -25,32 +25,51 @@ import android.view.View
 import org.isoron.platform.gui.toInt
 import org.isoron.uhabits.activities.common.views.FrequencyChart
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.ui.screens.habits.show.views.FrequencyCardPresenter
 import org.isoron.uhabits.core.ui.views.WidgetTheme
 import org.isoron.uhabits.widgets.views.GraphWidgetView
 
-class FrequencyWidget(
+class FrequencyWidget private constructor(
     context: Context,
     widgetId: Int,
-    private val habit: Habit,
+    private val habit: Habit?,
+    private val habitGroup: HabitGroup?,
     private val firstWeekday: Int,
-    stacked: Boolean = false
+    stacked: Boolean
 ) : BaseWidget(context, widgetId, stacked) {
+
+    constructor(context: Context, widgetId: Int, habit: Habit, firstWeekday: Int, stacked: Boolean = false) : this(context, widgetId, habit, null, firstWeekday, stacked)
+    constructor(context: Context, widgetId: Int, habitGroup: HabitGroup, firstWeekday: Int, stacked: Boolean = false) : this(context, widgetId, null, habitGroup, firstWeekday, stacked)
+
     override val defaultHeight: Int = 200
     override val defaultWidth: Int = 200
 
-    override fun getOnClickPendingIntent(context: Context): PendingIntent =
+    override fun getOnClickPendingIntent(context: Context): PendingIntent {
-        pendingIntentFactory.showHabit(habit)
+        return if (habit != null) {
+            pendingIntentFactory.showHabit(habit)
+        } else {
+            pendingIntentFactory.showHabitGroup(habitGroup!!)
+        }
+    }
 
     override fun refreshData(v: View) {
         val widgetView = v as GraphWidgetView
-        widgetView.setTitle(habit.name)
+        widgetView.setTitle(habit?.name ?: habitGroup!!.name)
         widgetView.setBackgroundAlpha(preferedBackgroundAlpha)
         if (preferedBackgroundAlpha >= 255) widgetView.setShadowAlpha(0x4f)
+        val color = habit?.color ?: habitGroup!!.color
+        val isNumerical = habit?.isNumerical ?: true
+        val frequency = if (habit != null) {
+            habit.originalEntries.computeWeekdayFrequency(habit.isNumerical)
+        } else {
+            FrequencyCardPresenter.getFrequenciesFromHabitGroup(habitGroup!!)
+        }
         (widgetView.dataView as FrequencyChart).apply {
             setFirstWeekday(firstWeekday)
-            setColor(WidgetTheme().color(habit.color).toInt())
+            setColor(WidgetTheme().color(color).toInt())
-            setIsNumerical(habit.isNumerical)
+            setIsNumerical(isNumerical)
-            setFrequency(habit.originalEntries.computeWeekdayFrequency(habit.isNumerical))
+            setFrequency(frequency)
         }
     }
 

uhabits-android/src/main/java/org/isoron/uhabits/widgets/FrequencyWidgetProvider.kt

@@ -24,15 +24,29 @@ import android.content.Context
 class FrequencyWidgetProvider : BaseWidgetProvider() {
     override fun getWidgetFromId(context: Context, id: Int): BaseWidget {
         val habits = getHabitsFromWidgetId(id)
-        return if (habits.size == 1) {
+        if (habits.isNotEmpty()) {
-            FrequencyWidget(
+            return if (habits.size == 1) {
-                context,
+                FrequencyWidget(
-                id,
+                    context,
-                habits[0],
+                    id,
-                preferences.firstWeekdayInt
+                    habits[0],
-            )
+                    preferences.firstWeekdayInt
+                )
+            } else {
+                StackWidget(context, id, StackWidgetType.FREQUENCY, habits)
+            }
         } else {
-            StackWidget(context, id, StackWidgetType.FREQUENCY, habits)
+            val habitGroups = getHabitGroupsFromWidgetId(id)
+            return if (habitGroups.size == 1) {
+                FrequencyWidget(
+                    context,
+                    id,
+                    habitGroups[0],
+                    preferences.firstWeekdayInt
+                )
+            } else {
+                StackWidget(context, id, StackWidgetType.FREQUENCY, habitGroups, true)
+            }
         }
     }
 }

uhabits-android/src/main/java/org/isoron/uhabits/widgets/ScoreWidget.kt

@@ -25,42 +25,62 @@ import android.view.View
 import org.isoron.platform.gui.toInt
 import org.isoron.uhabits.activities.common.views.ScoreChart
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.ui.screens.habits.show.views.ScoreCardPresenter
 import org.isoron.uhabits.core.ui.views.WidgetTheme
 import org.isoron.uhabits.widgets.views.GraphWidgetView
 
-class ScoreWidget(
+class ScoreWidget private constructor(
     context: Context,
     id: Int,
-    private val habit: Habit,
+    private val habit: Habit?,
-    stacked: Boolean = false
+    private val habitGroup: HabitGroup?,
+    stacked: Boolean
 ) : BaseWidget(context, id, stacked) {
+    constructor(context: Context, id: Int, habit: Habit, stacked: Boolean = false) : this(context, id, habit, null, stacked)
+    constructor(context: Context, id: Int, habitGroup: HabitGroup, stacked: Boolean = false) : this(context, id, null, habitGroup, stacked)
+
     override val defaultHeight: Int = 300
     override val defaultWidth: Int = 300
 
-    override fun getOnClickPendingIntent(context: Context): PendingIntent =
+    override fun getOnClickPendingIntent(context: Context): PendingIntent {
-        pendingIntentFactory.showHabit(habit)
+        return if (habit != null) {
+            pendingIntentFactory.showHabit(habit)
+        } else {
+            pendingIntentFactory.showHabitGroup(habitGroup!!)
+        }
+    }
 
     override fun refreshData(view: View) {
-        val viewModel = ScoreCardPresenter.buildState(
+        val viewModel = if (habit != null) {
-            habit = habit,
+            ScoreCardPresenter.buildState(
-            firstWeekday = prefs.firstWeekdayInt,
+                habit = habit,
-            spinnerPosition = prefs.scoreCardSpinnerPosition,
+                firstWeekday = prefs.firstWeekdayInt,
-            theme = WidgetTheme()
+                spinnerPosition = prefs.scoreCardSpinnerPosition,
-        )
+                theme = WidgetTheme()
+            )
+        } else {
+            ScoreCardPresenter.buildState(
+                habitGroup = habitGroup!!,
+                firstWeekday = prefs.firstWeekdayInt,
+                spinnerPosition = prefs.scoreCardSpinnerPosition,
+                theme = WidgetTheme()
+            )
+        }
         val widgetView = view as GraphWidgetView
         widgetView.setBackgroundAlpha(preferedBackgroundAlpha)
         if (preferedBackgroundAlpha >= 255) widgetView.setShadowAlpha(0x4f)
+        val color = habit?.color ?: habitGroup!!.color
         (widgetView.dataView as ScoreChart).apply {
             setIsTransparencyEnabled(true)
             setBucketSize(viewModel.bucketSize)
-            setColor(WidgetTheme().color(habit.color).toInt())
+            setColor(WidgetTheme().color(color).toInt())
             setScores(viewModel.scores)
         }
     }
 
     override fun buildView() =
         GraphWidgetView(context, ScoreChart(context)).apply {
-            setTitle(habit.name)
+            setTitle(habit?.name ?: habitGroup!!.name)
         }
 }

uhabits-android/src/main/java/org/isoron/uhabits/widgets/ScoreWidgetProvider.kt

@@ -23,10 +23,19 @@ import android.content.Context
 class ScoreWidgetProvider : BaseWidgetProvider() {
     override fun getWidgetFromId(context: Context, id: Int): BaseWidget {
         val habits = getHabitsFromWidgetId(id)
-        return if (habits.size == 1) {
+        if (habits.isNotEmpty()) {
-            ScoreWidget(context, id, habits[0])
+            return if (habits.size == 1) {
+                ScoreWidget(context, id, habits[0])
+            } else {
+                StackWidget(context, id, StackWidgetType.SCORE, habits)
+            }
         } else {
-            StackWidget(context, id, StackWidgetType.SCORE, habits)
+            val habitGroups = getHabitGroupsFromWidgetId(id)
+            return if (habitGroups.size == 1) {
+                ScoreWidget(context, id, habitGroups[0])
+            } else {
+                StackWidget(context, id, StackWidgetType.SCORE, habitGroups, true)
+            }
         }
     }
 }

uhabits-android/src/main/java/org/isoron/uhabits/widgets/StackWidget.kt

@@ -28,14 +28,20 @@ import android.view.View
 import android.widget.RemoteViews
 import org.isoron.platform.utils.StringUtils
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 
-class StackWidget(
+class StackWidget private constructor(
     context: Context,
     widgetId: Int,
     private val widgetType: StackWidgetType,
-    private val habits: List<Habit>,
+    private val habits: List<Habit>?,
-    stacked: Boolean = true
+    private val habitGroups: List<HabitGroup>?,
+    stacked: Boolean
 ) : BaseWidget(context, widgetId, stacked) {
+
+    constructor(context: Context, widgetId: Int, widgetType: StackWidgetType, habits: List<Habit>, stacked: Boolean = true) : this(context, widgetId, widgetType, habits, null, stacked)
+    constructor(context: Context, widgetId: Int, widgetType: StackWidgetType, habitGroups: List<HabitGroup>, stacked: Boolean = true, isHabitGroups: Boolean = false) : this(context, widgetId, widgetType, null, habitGroups, stacked)
+
     override val defaultHeight: Int = 0
     override val defaultWidth: Int = 0
 
@@ -55,7 +61,11 @@ class StackWidget(
         val remoteViews =
             RemoteViews(context.packageName, StackWidgetType.getStackWidgetLayoutId(widgetType))
         val serviceIntent = Intent(context, StackWidgetService::class.java)
-        val habitIds = StringUtils.joinLongs(habits.map { it.id!! }.toLongArray())
+        val habitIds = if (habits != null) {
+            StringUtils.joinLongs(habits.map { it.id!! }.toLongArray())
+        } else {
+            StringUtils.joinLongs(habitGroups!!.map { it.id!! }.toLongArray())
+        }
 
         serviceIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, id)
         serviceIntent.putExtra(StackWidgetService.WIDGET_TYPE, widgetType.value)
@@ -73,9 +83,14 @@ class StackWidget(
             StackWidgetType.getStackWidgetAdapterViewId(widgetType),
             StackWidgetType.getStackWidgetEmptyViewId(widgetType)
         )
+        val pendingIntentTemplate = if (habits != null) {
+            StackWidgetType.getPendingIntentTemplate(pendingIntentFactory, widgetType, habits)
+        } else {
+            StackWidgetType.getPendingIntentTemplate(pendingIntentFactory, widgetType, true)
+        }
         remoteViews.setPendingIntentTemplate(
             StackWidgetType.getStackWidgetAdapterViewId(widgetType),
-            StackWidgetType.getPendingIntentTemplate(pendingIntentFactory, widgetType, habits)
+            pendingIntentTemplate
         )
         return remoteViews
     }

uhabits-android/src/main/java/org/isoron/uhabits/widgets/StackWidgetType.kt

@@ -24,7 +24,6 @@ import org.isoron.uhabits.R
 import org.isoron.uhabits.core.models.Habit
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.intents.PendingIntentFactory
-import java.lang.IllegalStateException
 
 enum class StackWidgetType(val value: Int) {
     CHECKMARK(0), FREQUENCY(1), SCORE(2), // habit strength widget
@@ -95,6 +94,17 @@ enum class StackWidgetType(val value: Int) {
             }
         }
 
+        fun getPendingIntentTemplate(
+            factory: PendingIntentFactory,
+            widgetType: StackWidgetType,
+            isHabitGroups: Boolean
+        ): PendingIntent {
+            return when (widgetType) {
+                CHECKMARK, HISTORY, STREAKS, TARGET -> throw RuntimeException()
+                FREQUENCY, SCORE -> factory.showHabitGroupTemplate()
+            }
+        }
+
         fun getIntentFillIn(
             factory: PendingIntentFactory,
             widgetType: StackWidgetType,

uhabits-android/src/main/java/org/isoron/uhabits/widgets/activities/HabitPickerDialog.kt

@@ -25,7 +25,6 @@ import android.appwidget.AppWidgetManager.INVALID_APPWIDGET_ID
 import android.content.Intent
 import android.os.Bundle
 import android.widget.ArrayAdapter
-import android.widget.Button
 import android.widget.ListView
 import android.widget.TextView
 import org.isoron.uhabits.HabitsApplication
@@ -44,6 +43,10 @@ class NumericalHabitPickerDialog : HabitPickerDialog() {
     override fun getEmptyMessage() = R.string.no_numerical_habits
 }
 
+class HabitAndGroupPickerDialog : HabitPickerDialog() {
+    override fun shouldShowGroups(): Boolean = true
+}
+
 open class HabitPickerDialog : Activity() {
 
     private var widgetId = 0
@@ -52,6 +55,8 @@ open class HabitPickerDialog : Activity() {
 
     protected open fun shouldHideNumerical() = false
     protected open fun shouldHideBoolean() = false
+
+    protected open fun shouldShowGroups() = false
     protected open fun getEmptyMessage() = R.string.no_habits
 
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -59,6 +64,7 @@ open class HabitPickerDialog : Activity() {
         val component = (applicationContext as HabitsApplication).component
         AndroidThemeSwitcher(this, component.preferences).apply()
         val habitList = component.habitList
+        val habitGroupList = component.habitGroupList
         widgetPreferences = component.widgetPreferences
         widgetUpdater = component.widgetUpdater
         widgetId = intent.extras?.getInt(EXTRA_APPWIDGET_ID, INVALID_APPWIDGET_ID) ?: 0
@@ -73,6 +79,21 @@ open class HabitPickerDialog : Activity() {
             habitNames.add(h.name)
         }
 
+        for (hgr in habitGroupList) {
+            if (hgr.isArchived) continue
+            if (shouldShowGroups()) {
+                habitIds.add(hgr.id!!)
+                habitNames.add(hgr.name)
+            }
+
+            for (h in hgr.habitList) {
+                if (h.isArchived) continue
+                if (!h.isNumerical and shouldHideBoolean()) continue
+                habitIds.add(h.id!!)
+                habitNames.add(h.name)
+            }
+        }
+
         if (habitNames.isEmpty()) {
             setContentView(R.layout.widget_empty_activity)
             findViewById<TextView>(R.id.message).setText(getEmptyMessage())
@@ -81,7 +102,6 @@ open class HabitPickerDialog : Activity() {
 
         setContentView(R.layout.widget_configure_activity)
         val listView = findViewById<ListView>(R.id.listView)
-        val saveButton = findViewById<Button>(R.id.buttonSave)
 
         with(listView) {
             adapter = ArrayAdapter(

uhabits-android/src/main/res/layout/activity_edit_habit_group.xml

@@ -0,0 +1,163 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:background="?attr/contrast0"
+    android:fitsSystemWindows="true"
+    android:orientation="vertical"
+    tools:context=".activities.habits.edit.EditHabitGroupActivity">
+
+    <com.google.android.material.appbar.AppBarLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content">
+
+        <androidx.appcompat.widget.Toolbar
+            android:id="@+id/toolbar"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:background="?attr/colorPrimary"
+            android:elevation="2dp"
+            android:gravity="end"
+            android:minHeight="?attr/actionBarSize"
+            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
+            app:title="@string/create_habit_group"
+            app:titleTextColor="@color/white">
+
+            <com.google.android.material.button.MaterialButton
+                android:id="@+id/buttonSave"
+                style="@style/Widget.MaterialComponents.Button.OutlinedButton"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_gravity="end"
+                android:layout_marginEnd="16dp"
+                android:text="@string/save"
+                android:textColor="@color/white"
+                app:rippleColor="@color/white"
+                app:strokeColor="@color/white" />
+        </androidx.appcompat.widget.Toolbar>
+
+    </com.google.android.material.appbar.AppBarLayout>
+
+    <ScrollView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior">
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="vertical"
+            android:paddingTop="8dp"
+            android:paddingLeft="4dp"
+            android:paddingRight="4dp">
+
+            <!-- Title and color -->
+
+            <LinearLayout
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:orientation="horizontal"
+                android:baselineAligned="false">
+
+                <!-- Habit Title -->
+                <FrameLayout
+                    style="@style/FormOuterBox"
+                    android:layout_width="0dp"
+                    android:layout_weight="1">
+                    <LinearLayout style="@style/FormInnerBox">
+                        <TextView
+                            style="@style/FormLabel"
+                            android:text="@string/name" />
+                        <EditText
+                            android:id="@+id/nameInput"
+                            style="@style/FormInput"
+                            android:maxLines="1"
+                            android:inputType="textCapSentences"
+                            android:hint="@string/yes_or_no_short_example"
+                            />
+                    </LinearLayout>
+                </FrameLayout>
+
+                <!-- Habit Color -->
+                <FrameLayout
+                    style="@style/FormOuterBox"
+                    android:layout_width="80dp"
+                    android:layout_height="match_parent">
+                    <LinearLayout style="@style/FormInnerBox">
+                        <TextView
+                            style="@style/FormLabel"
+                            android:text="@string/color" />
+                        <androidx.appcompat.widget.AppCompatButton
+                            android:id="@+id/colorButton"
+                            android:layout_width="match_parent"
+                            android:layout_height="match_parent"
+                            android:layout_marginLeft="16dp"
+                            android:layout_marginTop="8dp"
+                            android:layout_marginRight="16dp"
+                            android:layout_marginBottom="8dp"
+                            android:backgroundTint="#E23673" />
+
+                    </LinearLayout>
+                </FrameLayout>
+            </LinearLayout>
+
+            <!-- Habit Question -->
+            <FrameLayout style="@style/FormOuterBox">
+                <LinearLayout style="@style/FormInnerBox">
+                    <TextView
+                        style="@style/FormLabel"
+                        android:text="@string/question" />
+                    <EditText
+                        android:id="@+id/questionInput"
+                        style="@style/FormInput"
+                        android:inputType="textCapSentences|textMultiLine"
+                        android:hint="@string/example_question_boolean"
+                        />
+                </LinearLayout>
+            </FrameLayout>
+
+            <!-- Reminder -->
+            <FrameLayout style="@style/FormOuterBox">
+                <LinearLayout style="@style/FormInnerBox">
+                    <TextView
+                        style="@style/FormLabel"
+                        android:text="@string/reminder" />
+
+                    <TextView
+                        style="@style/FormDropdown"
+                        android:id="@+id/reminderTimePicker"
+                        android:text="@string/reminder_off" />
+
+                    <View
+                        style="@style/FormDivider"
+                        android:id="@+id/reminderDivider"/>
+
+                    <TextView
+                        style="@style/FormDropdown"
+                        android:id="@+id/reminderDatePicker"
+                        android:text="" />
+                </LinearLayout>
+            </FrameLayout>
+
+
+            <!-- Notes -->
+            <FrameLayout style="@style/FormOuterBox">
+                <LinearLayout style="@style/FormInnerBox">
+                    <TextView
+                        style="@style/FormLabel"
+                        android:text="@string/notes" />
+
+                    <EditText
+                        android:id="@+id/notesInput"
+                        style="@style/FormInput"
+                        android:inputType="textCapSentences|textMultiLine"
+                        android:hint="@string/example_notes" />
+                </LinearLayout>
+            </FrameLayout>
+        </LinearLayout>
+    </ScrollView>
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>

uhabits-android/src/main/res/layout/select_habit_type.xml

@@ -67,6 +67,25 @@
             android:text="@string/measurable_example" />
     </LinearLayout>
 
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:id="@+id/buttonHabitGroup"
+        style="@style/SelectHabitTypeButton">
+
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            style="@style/SelectHabitTypeButtonTitle"
+            android:text="@string/habit_group" />
+
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            style="@style/SelectHabitTypeButtonBody"
+            android:text="@string/habit_group_example" />
+    </LinearLayout>
+
 <!--    <LinearLayout-->
 <!--        android:layout_width="match_parent"-->
 <!--        android:layout_height="wrap_content"-->

uhabits-android/src/main/res/layout/show_habit_group.xml

@@ -0,0 +1,101 @@
+<!--
+  ~ Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+  ~
+  ~ This file is part of Loop Habit Tracker.
+  ~
+  ~ Loop Habit Tracker is free software: you can redistribute it and/or modify
+  ~ it under the terms of the GNU General Public License as published by the
+  ~ Free Software Foundation, either version 3 of the License, or (at your
+  ~ option) any later version.
+  ~
+  ~ Loop Habit Tracker is distributed in the hope that it will be useful, but
+  ~ WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+  ~ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+  ~ more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along
+  ~ with this program. If not, see <http://www.gnu.org/licenses/>.
+  -->
+
+<RelativeLayout
+    android:id="@+id/container"
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <androidx.appcompat.widget.Toolbar
+        android:id="@+id/toolbar"
+        style="@style/Toolbar"
+        app:popupTheme="?toolbarPopupTheme"
+        android:layout_alignParentTop="true"/>
+
+    <ScrollView
+        android:id="@+id/scrollView"
+        android:layout_width="fill_parent"
+        android:layout_height="wrap_content"
+        android:layout_below="@id/toolbar"
+        android:background="?windowBackgroundColor"
+        android:clipToPadding="false">
+
+        <LinearLayout
+            style="@style/CardList"
+            android:clipToPadding="false">
+
+            <org.isoron.uhabits.activities.habits.show.views.SubtitleCardView
+                android:id="@+id/subtitleCard"
+                style="@style/ShowHabit.Subtitle"/>
+
+            <org.isoron.uhabits.activities.habits.show.views.NotesCardView
+                android:id="@+id/notesCard"
+                style="@style/Card"
+                android:gravity="center" />
+
+            <org.isoron.uhabits.activities.habits.show.views.OverviewCardView
+                android:id="@+id/overviewCard"
+                style="@style/Card"
+                android:paddingTop="12dp"/>
+
+            <FrameLayout
+                android:id="@+id/noSubHabitsCard"
+                style="@style/Card"
+                android:layout_width="match_parent"
+                android:layout_height="match_parent"
+                android:paddingTop="12dp"
+                android:visibility="gone">
+
+                <TextView
+                    android:id="@+id/textView"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:text="@string/no_sub_habits" />
+            </FrameLayout>
+
+            <org.isoron.uhabits.activities.habits.show.views.TargetCardView
+                android:id="@+id/targetCard"
+                style="@style/Card"
+                android:paddingTop="12dp"/>
+
+            <org.isoron.uhabits.activities.habits.show.views.ScoreCardView
+                android:id="@+id/scoreCard"
+                style="@style/Card"
+                android:gravity="center"/>
+
+            <org.isoron.uhabits.activities.habits.show.views.BarCardView
+                android:id="@+id/barCard"
+                style="@style/Card"
+                android:gravity="center"/>
+
+            <org.isoron.uhabits.activities.habits.show.views.StreakCardView
+                android:id="@+id/streakCard"
+                style="@style/Card"/>
+
+            <org.isoron.uhabits.activities.habits.show.views.FrequencyCardView
+                android:id="@+id/frequencyCard"
+                style="@style/Card"/>
+
+        </LinearLayout>
+    </ScrollView>
+
+</RelativeLayout>

uhabits-android/src/main/res/layout/show_habit_subtitle.xml

@@ -76,7 +76,7 @@
             android:text="@string/every_day"
             android:textColor="?attr/contrast60"
             android:layout_marginStart="4dp"
-            android:layout_marginEnd="16dp"
+            android:layout_marginEnd="8dp"
             android:textSize="@dimen/smallTextSize" />
 
         <TextView
@@ -92,10 +92,31 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:paddingTop="1dp"
-            android:textColor="?attr/contrast60"
             android:text="8:00 AM"
             android:layout_marginStart="4dp"
             android:textSize="@dimen/smallTextSize" />
 
     </LinearLayout>
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="2dp"
+        android:gravity="center_vertical"
+        android:orientation="horizontal"
+        tools:visibility="visible">
+
+        <TextView
+            android:id="@+id/skipLabel"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:paddingTop="1dp"
+            android:textColor="?attr/contrast60"
+            android:text=""
+            android:layout_marginStart="4dp"
+            android:layout_marginEnd="16dp"
+            android:textSize="@dimen/smallTextSize" />
+
+    </LinearLayout>
+
+
 </merge>

uhabits-android/src/main/res/menu/list_habits_selection.xml

@@ -41,6 +41,16 @@
         android:title="@string/unarchive"
         app:showAsAction="never"/>
 
+    <item
+        android:id="@+id/action_add_to_group"
+        android:title="@string/add_to_group"
+        app:showAsAction="never"/>
+
+    <item
+        android:id="@+id/action_remove_from_group"
+        android:title="@string/remove_from_group"
+        app:showAsAction="never"/>
+
     <item
         android:id="@+id/action_delete"
         android:title="@string/delete"

uhabits-android/src/main/res/menu/show_habit_group.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+  ~
+  ~ This file is part of Loop Habit Tracker.
+  ~
+  ~ Loop Habit Tracker is free software: you can redistribute it and/or modify
+  ~ it under the terms of the GNU General Public License as published by the
+  ~ Free Software Foundation, either version 3 of the License, or (at your
+  ~ option) any later version.
+  ~
+  ~ Loop Habit Tracker is distributed in the hope that it will be useful, but
+  ~ WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+  ~ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+  ~ more details.
+  ~
+  ~ You should have received a copy of the GNU General Public License along
+  ~ with this program. If not, see <http://www.gnu.org/licenses/>.
+  -->
+
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+      xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/action_delete"
+        android:title="@string/delete"
+        app:showAsAction="never"/>
+
+    <item
+        android:id="@+id/action_edit_habit_group"
+        android:icon="?iconEdit"
+        android:title="@string/edit"
+        app:showAsAction="ifRoom"/>
+
+</menu>

uhabits-android/src/main/res/values/fontawesome.xml

@@ -24,6 +24,9 @@
 	<string translatable="false" name="fa_arrow_circle_down">&#xf0ab;</string>
 	<string translatable="false" name="fa_check">&#xf00c;</string>
 	<string translatable="false" name="fa_times">&#xf00d;</string>
+	<string translatable="false" name="fa_plus">&#xf067;</string>
+	<string translatable="false" name="fa_angle_left">&#xf053;</string>
+	<string translatable="false" name="fa_angle_down">&#xf078;</string>
 	<string translatable="false" name="fa_skipped">&#xf068;</string>
     <string translatable="false" name="fa_bell_o">&#xf0f3;</string>
 	<string translatable="false" name="fa_calendar">&#xf073;</string>

uhabits-android/src/main/res/values/strings.xml

@@ -29,6 +29,8 @@
     <string name="delete">Delete</string>
     <string name="archive">Archive</string>
     <string name="unarchive">Unarchive</string>
+    <string name="remove_from_group">Remove from group</string>
+    <string name="add_to_group">Add to group</string>
     <string name="add_habit">Add habit</string>
     <string name="color_picker_default_title">Change color</string>
     <string name="toast_habit_created">Habit created</string>
@@ -62,6 +64,8 @@
     <string name="reminder_off">Off</string>
     <string name="create_habit">Create habit</string>
     <string name="edit_habit">Edit habit</string>
+    <string name="create_habit_group">Create habit group</string>
+    <string name="edit_habit_group">Edit habit group</string>
     <string name="check">Check</string>
     <string name="snooze">Later</string>
     <string name="intro_title_1">Welcome</string>
@@ -206,6 +210,8 @@
     <string name="yes_or_no_example">e.g. Did you wake up early today? Did you exercise? Did you play chess?</string>
     <string name="measurable">Measurable</string>
     <string name="measurable_example">e.g. How many miles did you run today? How many pages did you read?</string>
+    <string name="habit_group">Habit Group</string>
+    <string name="habit_group_example">A group to organize similar habits together. E.g. Exercise: Running, Cycling, Gym, etc.</string>
     <string name="x_times_per_week">%d times per week</string>
     <string name="x_times_per_month">%d times per month</string>
     <string name="x_times_per_y_days">%d times in %d days</string>
@@ -233,4 +239,6 @@
     <string name="activity_not_found">No app was found to support this action</string>
     <string name="pref_midnight_delay_title">Extend day a few hours past midnight</string>
     <string name="pref_midnight_delay_description">Wait until 3:00 AM to show a new day. Useful if you typically go to sleep after midnight. Requires app restart.</string>
+    <string name="no_sub_habits">Group contains no habits.</string>
+    <string name="no_habit_groups">No habit groups</string>
 </resources>

uhabits-android/src/main/res/xml/widget_frequency_info.xml

@@ -27,7 +27,7 @@
                     android:previewImage="@drawable/widget_preview_frequency"
                     android:resizeMode="vertical|horizontal"
                     android:updatePeriodMillis="3600000"
-                    android:configure="org.isoron.uhabits.widgets.activities.HabitPickerDialog"
+                    android:configure="org.isoron.uhabits.widgets.activities.HabitAndGroupPickerDialog"
                     android:widgetCategory="home_screen">
 
 </appwidget-provider>

uhabits-android/src/main/res/xml/widget_score_info.xml

@@ -27,7 +27,7 @@
                     android:previewImage="@drawable/widget_preview_score"
                     android:resizeMode="vertical|horizontal"
                     android:updatePeriodMillis="3600000"
-                    android:configure="org.isoron.uhabits.widgets.activities.HabitPickerDialog"
+                    android:configure="org.isoron.uhabits.widgets.activities.HabitAndGroupPickerDialog"
                     android:widgetCategory="home_screen">
 
 </appwidget-provider>

uhabits-core-legacy/assets/main/migrations/024.sql

@@ -0,0 +1,2 @@
+alter table Habits add column skip_days integer not null default 0
+alter table Habits add column skip_days_list integer not null default 0

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/Constants.kt

@@ -20,4 +20,4 @@ package org.isoron.uhabits.core
 
 const val DATABASE_FILENAME = "uhabits.db"
 
-const val DATABASE_VERSION = 25
+const val DATABASE_VERSION = 26

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/AddToGroupCommand.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitList
+
+data class AddToGroupCommand(
+    val habitList: HabitList,
+    val hgr: HabitGroup,
+    val selected: List<Habit>
+) : Command {
+    override fun run() {
+        for (habit in selected) {
+            val entries = habit.originalEntries.getKnown()
+            val oldGroup = habit.group
+            (oldGroup?.habitList ?: habitList).remove(habit)
+            habit.groupId = hgr.id
+            habit.groupUUID = hgr.uuid
+            habit.group = hgr
+            hgr.habitList.add(habit)
+            entries.forEach { habit.originalEntries.add(it) }
+            habit.observable.notifyListeners()
+        }
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/ArchiveHabitGroupsCommand.kt

@@ -0,0 +1,19 @@
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+
+data class ArchiveHabitGroupsCommand(
+    val habitGroupList: HabitGroupList,
+    val selected: List<HabitGroup>
+) : Command {
+    override fun run() {
+        for (hgr in selected) {
+            hgr.isArchived = true
+            for (h in hgr.habitList) {
+                h.isArchived = true
+            }
+        }
+        habitGroupList.update(selected)
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/ChangeHabitGroupColorCommand.kt

@@ -0,0 +1,16 @@
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.PaletteColor
+
+data class ChangeHabitGroupColorCommand(
+    val habitGroupList: HabitGroupList,
+    val selected: List<HabitGroup>,
+    val newColor: PaletteColor
+) : Command {
+    override fun run() {
+        for (hgr in selected) hgr.color = newColor
+        habitGroupList.update(selected)
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/CreateHabitGroupCommand.kt

@@ -0,0 +1,18 @@
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.ModelFactory
+
+data class CreateHabitGroupCommand(
+    val modelFactory: ModelFactory,
+    val habitGroupList: HabitGroupList,
+    val model: HabitGroup
+) : Command {
+    override fun run() {
+        val habitGroup = modelFactory.buildHabitGroup()
+        habitGroup.copyFrom(model)
+        habitGroupList.add(habitGroup)
+        habitGroup.recompute()
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/DeleteHabitGroupsCommand.kt

@@ -0,0 +1,13 @@
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+
+data class DeleteHabitGroupsCommand(
+    val habitGroupList: HabitGroupList,
+    val selected: List<HabitGroup>
+) : Command {
+    override fun run() {
+        for (hgr in selected) habitGroupList.remove(hgr)
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/DeleteHabitsCommand.kt

@@ -19,6 +19,7 @@
 package org.isoron.uhabits.core.commands
 
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.HabitList
 
 data class DeleteHabitsCommand(
@@ -26,6 +27,13 @@ data class DeleteHabitsCommand(
     val selected: List<Habit>
 ) : Command {
     override fun run() {
-        for (h in selected) habitList.remove(h)
+        for (h in selected) {
+            if (!h.isSubHabit()) {
+                habitList.remove(h)
+            } else {
+                val list = (h.group as HabitGroup).habitList
+                list.remove(h)
+            }
+        }
     }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/EditHabitGroupCommand.kt

@@ -0,0 +1,20 @@
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.HabitNotFoundException
+
+data class EditHabitGroupCommand(
+    val habitGroupList: HabitGroupList,
+    val habitGroupId: Long,
+    val modified: HabitGroup
+) : Command {
+    override fun run() {
+        val habitGroup = habitGroupList.getById(habitGroupId) ?: throw HabitNotFoundException()
+        habitGroup.copyFrom(modified)
+        habitGroupList.update(habitGroup)
+        habitGroup.observable.notifyListeners()
+        habitGroup.recompute()
+        habitGroupList.resort()
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/RefreshParentGroupCommand.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroupList
+
+data class RefreshParentGroupCommand(
+    val habit: Habit,
+    val habitGroupList: HabitGroupList
+) : Command {
+    override fun run() {
+        if (!habit.isSubHabit()) return
+        val hgr = habit.group
+        hgr!!.recompute()
+        habitGroupList.resort()
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/RemoveFromGroupCommand.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitList
+
+data class RemoveFromGroupCommand(
+    val habitList: HabitList,
+    val selected: List<Habit>
+) : Command {
+    override fun run() {
+        for (habit in selected) {
+            val hgr = habit.group!!
+            val entries = habit.originalEntries.getKnown()
+            hgr.habitList.remove(habit)
+            habit.groupId = null
+            habit.group = null
+            habit.groupUUID = null
+            habitList.add(habit)
+            entries.forEach { habit.originalEntries.add(it) }
+            habit.observable.notifyListeners()
+        }
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/commands/UnarchiveHabitGroupsCommand.kt

@@ -0,0 +1,19 @@
+package org.isoron.uhabits.core.commands
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+
+data class UnarchiveHabitGroupsCommand(
+    val habitGroupList: HabitGroupList,
+    val selected: List<HabitGroup>
+) : Command {
+    override fun run() {
+        for (hgr in selected) {
+            hgr.isArchived = false
+            for (h in hgr.habitList) {
+                h.isArchived = false
+            }
+        }
+        habitGroupList.update(selected)
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/database/JdbcDatabase.kt

@@ -24,7 +24,6 @@ import java.sql.Connection
 import java.sql.PreparedStatement
 import java.sql.SQLException
 import java.sql.Types
-import java.util.ArrayList
 
 class JdbcDatabase(private val connection: Connection) : Database {
     private var transactionSuccessful = false
@@ -51,6 +50,14 @@ class JdbcDatabase(private val connection: Connection) : Database {
                 valuesStr.add(value.toString())
             }
             valuesStr.addAll(listOf(*params))
+            if (tableName == "habits") {
+                val groupIdx = fields.indexOf("group_id=?")
+                if (valuesStr[groupIdx] == "null") {
+                    valuesStr.removeAt(groupIdx)
+                    fields.removeAt(groupIdx)
+                }
+            }
+
             val query = String.format(
                 "update %s set %s where %s",
                 tableName,

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/database/Repository.kt

@@ -22,8 +22,6 @@ import org.apache.commons.lang3.StringUtils
 import org.apache.commons.lang3.tuple.ImmutablePair
 import org.apache.commons.lang3.tuple.Pair
 import java.lang.reflect.Field
-import java.util.ArrayList
-import java.util.HashMap
 import java.util.LinkedList
 
 class Repository<T>(
@@ -130,6 +128,26 @@ class Repository<T>(
         }
     }
 
+    /**
+     * Gets the shared id for tables that need to maintain unique ids across tables
+     * like habits and habit groups
+     */
+
+    fun getNextAvailableId(name: String): Long {
+        val query = "SELECT next_id FROM SharedIds WHERE name = ?"
+        val cursor = db.query(query, name)
+        val nextId: Long
+        cursor.use { c ->
+            if (cursor.moveToNext()) {
+                nextId = cursor.getLong(0) ?: throw IllegalStateException("Cannot fetch shared ID for $name")
+                execSQL("UPDATE SharedIds SET next_id = next_id + 1 WHERE name = ?", name)
+            } else {
+                throw IllegalStateException("Cannot fetch shared ID for $name")
+            }
+        }
+        return nextId
+    }
+
     private fun cursorToMultipleRecords(c: Cursor): List<T> {
         val records: MutableList<T> = LinkedList()
         while (c.moveToNext()) records.add(cursorToSingleRecord(c))

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/io/LoopDBImporter.kt

@@ -22,15 +22,19 @@ import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.DATABASE_VERSION
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateHabitCommand
+import org.isoron.uhabits.core.commands.CreateHabitGroupCommand
 import org.isoron.uhabits.core.commands.EditHabitCommand
+import org.isoron.uhabits.core.commands.EditHabitGroupCommand
 import org.isoron.uhabits.core.database.DatabaseOpener
 import org.isoron.uhabits.core.database.MigrationHelper
 import org.isoron.uhabits.core.database.Repository
 import org.isoron.uhabits.core.models.Entry
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.ModelFactory
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.models.sqlite.records.EntryRecord
+import org.isoron.uhabits.core.models.sqlite.records.HabitGroupRecord
 import org.isoron.uhabits.core.models.sqlite.records.HabitRecord
 import org.isoron.uhabits.core.utils.isSQLite3File
 import java.io.File
@@ -42,6 +46,7 @@ import javax.inject.Inject
 class LoopDBImporter
 @Inject constructor(
     @AppScope val habitList: HabitList,
+    @AppScope val habitGroupList: HabitGroupList,
     @AppScope val modelFactory: ModelFactory,
     @AppScope val opener: DatabaseOpener,
     @AppScope val runner: CommandRunner,
@@ -74,26 +79,66 @@ class LoopDBImporter
         helper.migrateTo(DATABASE_VERSION)
 
         val habitsRepository = Repository(HabitRecord::class.java, db)
+        val habitGroupsRepository = Repository(HabitGroupRecord::class.java, db)
         val entryRepository = Repository(EntryRecord::class.java, db)
 
+        for (groupRecord in habitGroupsRepository.findAll("order by position")) {
+            var hgr = habitGroupList.getByUUID(groupRecord.uuid)
+
+            if (hgr == null) {
+                hgr = modelFactory.buildHabitGroup()
+                groupRecord.id = null
+                groupRecord.copyTo(hgr)
+                CreateHabitGroupCommand(modelFactory, habitGroupList, hgr).run()
+            } else {
+                val modified = modelFactory.buildHabitGroup()
+                groupRecord.id = hgr.id
+                groupRecord.copyTo(modified)
+                EditHabitGroupCommand(habitGroupList, hgr.id!!, modified).run()
+            }
+        }
+
         for (habitRecord in habitsRepository.findAll("order by position")) {
-            var habit = habitList.getByUUID(habitRecord.uuid)
+            var habit = habitList.getByUUID(habitRecord.uuid) ?: habitGroupList.getHabitByUUID(habitRecord.uuid)
             val entryRecords = entryRepository.findAll("where habit = ?", habitRecord.id.toString())
 
             if (habit == null) {
                 habit = modelFactory.buildHabit()
                 habitRecord.id = null
                 habitRecord.copyTo(habit)
-                CreateHabitCommand(modelFactory, habitList, habit).run()
+                val list = if (habit.groupId != null) {
+                    val hgr = habitGroupList.getByUUID(habit.groupUUID)
+                    if (hgr != null) {
+                        habit.group = hgr
+                        habit.groupId = hgr.id
+                        hgr.habitList
+                    } else {
+                        habit.group = null
+                        habit.groupId = null
+                        habit.groupUUID = null
+                        habitList
+                    }
+                } else {
+                    habitList
+                }
+                CreateHabitCommand(modelFactory, list, habit).run()
             } else {
                 val modified = modelFactory.buildHabit()
                 habitRecord.id = habit.id
                 habitRecord.copyTo(modified)
-                EditHabitCommand(habitList, habit.id!!, modified).run()
+                val list = if (habit.group != null) {
+                    modified.group = habit.group
+                    modified.groupId = habit.groupId
+                    modified.groupUUID = habit.groupUUID
+                    habit.group!!.habitList
+                } else {
+                    habitList
+                }
+                EditHabitCommand(list, habit.id!!, modified).run()
             }
 
             // Reload saved version of the habit
-            habit = habitList.getByUUID(habitRecord.uuid)!!
+            habit = habitList.getByUUID(habitRecord.uuid) ?: habitGroupList.getHabitByUUID(habitRecord.uuid)!!
             val entries = habit.originalEntries
 
             // Import entries
@@ -106,6 +151,9 @@ class LoopDBImporter
             }
             habit.recompute()
         }
+
+        habitGroupList.forEach { it.recompute() }
+        habitGroupList.resort()
         habitList.resort()
         db.close()
     }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/EntryList.kt

@@ -24,12 +24,12 @@ import org.isoron.uhabits.core.models.Entry.Companion.UNKNOWN
 import org.isoron.uhabits.core.models.Entry.Companion.YES_AUTO
 import org.isoron.uhabits.core.models.Entry.Companion.YES_MANUAL
 import org.isoron.uhabits.core.utils.DateUtils
-import java.util.ArrayList
 import java.util.Calendar
 import javax.annotation.concurrent.ThreadSafe
 import kotlin.collections.set
 import kotlin.math.max
 import kotlin.math.min
+import kotlin.math.roundToInt
 
 @ThreadSafe
 open class EntryList {
@@ -151,6 +151,22 @@ open class EntryList {
         return map
     }
 
+    @Synchronized fun normalizeEntries(
+        isNumerical: Boolean,
+        frequency: Frequency,
+        targetValue: Double
+    ): EntryList {
+        val entries = getKnown()
+        val normalized = EntryList()
+        val dailyTarget = frequency.toDouble() * (if (isNumerical) targetValue else 0.001)
+        for (entry in entries) {
+            if (!isNumerical && entry.value != YES_MANUAL) continue
+            val newValue = (entry.value.toDouble() / dailyTarget).roundToInt()
+            normalized.add(Entry(entry.timestamp, newValue))
+        }
+        return normalized
+    }
+
     data class Interval(val begin: Timestamp, val center: Timestamp, val end: Timestamp) {
         val length: Int
             get() = begin.daysUntil(end) + 1
@@ -318,6 +334,16 @@ fun List<Entry>.groupedSum(
     }
 }
 
+fun List<Entry>.groupedSum(): List<Entry> {
+    return this
+        .groupBy { entry -> entry.timestamp }
+        .entries.map { (timestamp, entries) ->
+            Entry(timestamp, entries.sumOf { it.value })
+        }.sortedBy { (timestamp, _) ->
+            -timestamp.unixTime
+        }
+}
+
 /**
  * Counts the number of days with vaLue SKIP in the given period.
  */

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/Habit.kt

@@ -39,12 +39,15 @@ data class Habit(
     val computedEntries: EntryList,
     val originalEntries: EntryList,
     val scores: ScoreList,
-    val streaks: StreakList
+    val streaks: StreakList,
+    var groupId: Long? = null,
+    var groupUUID: String? = null
 ) {
     init {
         if (uuid == null) this.uuid = UUID.randomUUID().toString().replace("-", "")
     }
 
+    var group: HabitGroup? = null
     var observable = ModelObservable()
 
     val isNumerical: Boolean
@@ -53,6 +56,10 @@ data class Habit(
     val uriString: String
         get() = "content://org.isoron.uhabits/habit/$id"
 
+    var collapsed = false
+
+    fun isSubHabit(): Boolean = groupUUID != null
+
     fun hasReminder(): Boolean = reminder != null
 
     fun isCompletedToday(): Boolean {
@@ -104,6 +111,10 @@ data class Habit(
         )
     }
 
+    fun firstEntryDate(): Timestamp {
+        return computedEntries.getKnown().lastOrNull()?.timestamp ?: DateUtils.getTodayWithOffset()
+    }
+
     fun copyFrom(other: Habit) {
         this.color = other.color
         this.description = other.description
@@ -119,6 +130,9 @@ data class Habit(
         this.type = other.type
         this.unit = other.unit
         this.uuid = other.uuid
+        this.group = other.group
+        this.groupId = other.groupId
+        this.groupUUID = other.groupUUID
     }
 
     override fun equals(other: Any?): Boolean {
@@ -139,6 +153,8 @@ data class Habit(
         if (type != other.type) return false
         if (unit != other.unit) return false
         if (uuid != other.uuid) return false
+        if (groupId != other.groupId) return false
+        if (groupUUID != other.groupUUID) return false
 
         return true
     }
@@ -158,6 +174,8 @@ data class Habit(
         result = 31 * result + type.value
         result = 31 * result + unit.hashCode()
         result = 31 * result + (uuid?.hashCode() ?: 0)
+        result = 31 * result + (groupId?.hashCode() ?: 0)
+        result = 31 * result + (groupUUID?.hashCode() ?: 0)
         return result
     }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/HabitGroup.kt

@@ -0,0 +1,148 @@
+package org.isoron.uhabits.core.models
+
+import org.isoron.uhabits.core.utils.DateUtils
+import java.util.UUID
+
+data class HabitGroup(
+    var color: PaletteColor = PaletteColor(8),
+    var description: String = "",
+    var id: Long? = null,
+    var isArchived: Boolean = false,
+    var name: String = "",
+    var position: Int = 0,
+    var question: String = "",
+    var reminder: Reminder? = null,
+    var uuid: String? = null,
+    var habitList: HabitList,
+    val scores: ScoreList,
+    val streaks: StreakList
+) {
+
+    constructor(
+        parent: HabitGroup,
+        matcher: HabitMatcher
+    ) : this(
+        parent.color,
+        parent.description,
+        parent.id,
+        parent.isArchived,
+        parent.name,
+        parent.position,
+        parent.question,
+        parent.reminder,
+        parent.uuid,
+        parent.habitList.getFiltered(matcher),
+        parent.scores,
+        parent.streaks
+    ) {
+        this.collapsed = parent.collapsed
+        this.parent = parent
+    }
+
+    init {
+        if (uuid == null) this.uuid = UUID.randomUUID().toString().replace("-", "")
+    }
+
+    var observable = ModelObservable()
+
+    var parent: HabitGroup? = null
+
+    val uriString: String
+        get() = "content://org.isoron.uhabits/habitgroup/$id"
+
+    var collapsed = false
+        set(value) {
+            field = value
+            habitList.collapsed = value
+            if (parent != null) parent!!.collapsed = value
+        }
+
+    fun hasReminder(): Boolean = reminder != null
+
+    fun isCompletedToday(): Boolean {
+        if (habitList.isEmpty) return false
+        return habitList.all { it.isCompletedToday() }
+    }
+
+    fun isEnteredToday(): Boolean {
+        if (habitList.isEmpty) return false
+        return habitList.all { it.isEnteredToday() }
+    }
+
+    fun firstEntryDate(): Timestamp {
+        val today = DateUtils.getTodayWithOffset()
+        var earliest = today
+        for (h in habitList) {
+            val first = h.firstEntryDate()
+            if (earliest.isNewerThan(first)) earliest = first
+        }
+        return earliest
+    }
+
+    fun recompute() {
+        for (h in habitList) h.recompute()
+
+        val today = DateUtils.getTodayWithOffset()
+        val to = today.plus(30)
+        var from = firstEntryDate()
+        if (from.isNewerThan(to)) from = to
+
+        scores.combineFrom(
+            habitList = habitList,
+            from = from,
+            to = to
+        )
+
+        streaks.combineFrom(
+            habitList = habitList,
+            from = from,
+            to = to
+        )
+    }
+
+    fun copyFrom(other: HabitGroup) {
+        this.color = other.color
+        this.description = other.description
+        // this.id should not be copied
+        this.isArchived = other.isArchived
+        this.name = other.name
+        this.position = other.position
+        this.question = other.question
+        this.reminder = other.reminder
+        this.uuid = other.uuid
+        this.habitList.groupId = this.id
+    }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is HabitGroup) return false
+
+        if (color != other.color) return false
+        if (description != other.description) return false
+        if (id != other.id) return false
+        if (isArchived != other.isArchived) return false
+        if (name != other.name) return false
+        if (position != other.position) return false
+        if (question != other.question) return false
+        if (reminder != other.reminder) return false
+        if (uuid != other.uuid) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = color.hashCode()
+        result = 31 * result + description.hashCode()
+        result = 31 * result + (id?.hashCode() ?: 0)
+        result = 31 * result + isArchived.hashCode()
+        result = 31 * result + name.hashCode()
+        result = 31 * result + position
+        result = 31 * result + question.hashCode()
+        result = 31 * result + (reminder?.hashCode() ?: 0)
+        result = 31 * result + (uuid?.hashCode() ?: 0)
+        return result
+    }
+
+    fun getHabitByUUID(uuid: String?): Habit? =
+        habitList.getByUUID(uuid)
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/HabitGroupList.kt

@@ -0,0 +1,221 @@
+package org.isoron.uhabits.core.models
+
+import com.opencsv.CSVWriter
+import org.isoron.uhabits.core.models.HabitList.Order
+import java.io.IOException
+import java.io.Writer
+import java.util.LinkedList
+import javax.annotation.concurrent.ThreadSafe
+
+/**
+ * An ordered collection of [HabitGroup]s.
+ */
+@ThreadSafe
+abstract class HabitGroupList : Iterable<HabitGroup> {
+    val observable: ModelObservable
+
+    @JvmField
+    protected val filter: HabitMatcher
+
+    /**
+     * Creates a new HabitGroupList.
+     *
+     * Depending on the implementation, this list can either be empty or be
+     * populated by some pre-existing habitgroups, for example, from a certain
+     * database.
+     */
+    constructor() {
+        observable = ModelObservable()
+        filter = HabitMatcher(isArchivedAllowed = true)
+    }
+
+    protected constructor(filter: HabitMatcher) {
+        observable = ModelObservable()
+        this.filter = filter
+    }
+
+    /**
+     * Inserts a new habit group in the list.
+     *
+     * If the id of the habit group is null, the list will assign it a new id, which
+     * is guaranteed to be unique in the scope of the list. If id is not null,
+     * the caller should make sure that the list does not already contain
+     * another habit group with same id, otherwise a RuntimeException will be thrown.
+     *
+     * @param habitGroup the habit to be inserted
+     * @throws IllegalArgumentException if the habit is already on the list.
+     */
+    @Throws(IllegalArgumentException::class)
+    abstract fun add(habitGroup: HabitGroup)
+
+    /**
+     * Returns the habit group with specified id.
+     *
+     * @param id the id of the habit group
+     * @return the habit group, or null if none exist
+     */
+    abstract fun getById(id: Long): HabitGroup?
+
+    /**
+     * Returns the habit group with specified UUID.
+     *
+     * @param uuid the UUID of the habit group
+     * @return the habit group, or null if none exist
+     */
+    abstract fun getByUUID(uuid: String?): HabitGroup?
+
+    /**
+     *  Returns the habit with the specified UUID which is
+     *  present in any of the habit groups within this habit group list.
+     */
+    fun getHabitByUUID(uuid: String?): Habit? {
+        for (hgr in this) {
+            val habit = hgr.getHabitByUUID(uuid)
+            if (habit != null) {
+                return habit
+            }
+        }
+        return null
+    }
+
+    /**
+     *  Returns the habit with the specified UUID which is
+     *  present in any of the habit groups within this habit group list.
+     */
+    fun getHabitByID(id: Long): Habit? {
+        for (hgr in this) {
+            val habit = hgr.habitList.getById(id)
+            if (habit != null) {
+                return habit
+            }
+        }
+        return null
+    }
+
+    /**
+     * Returns the habit group that occupies a certain position.
+     *
+     * @param position the position of the desired habit group
+     * @return the habit group at that position
+     * @throws IndexOutOfBoundsException when the position is invalid
+     */
+    abstract fun getByPosition(position: Int): HabitGroup
+
+    /**
+     * Returns the list of habit groups that match a given condition.
+     *
+     * @param matcher the matcher that checks the condition
+     * @return the list of matching habit groups
+     */
+    abstract fun getFiltered(matcher: HabitMatcher?): HabitGroupList
+    abstract var primaryOrder: Order
+    abstract var secondaryOrder: Order
+
+    /**
+     * Returns the index of the given habit group in the list, or -1 if the list does
+     * not contain the habit group.
+     *
+     * @param h the habit group
+     * @return the index of the habit group, or -1 if not in the list
+     */
+    abstract fun indexOf(h: HabitGroup): Int
+    val isEmpty: Boolean
+        get() = size() == 0
+
+    /**
+     * Removes the given habit group from the list.
+     *
+     * If the given habit group is not in the list, does nothing.
+     *
+     * @param h the habit group to be removed.
+     */
+    abstract fun remove(h: HabitGroup)
+
+    /**
+     * Removes all the habit groups from the list.
+     */
+    open fun removeAll() {
+        val copy: MutableList<HabitGroup> = LinkedList()
+        for (h in this) copy.add(h)
+        for (h in copy) remove(h)
+        observable.notifyListeners()
+    }
+
+    /**
+     * Changes the position of a habit group in the list.
+     *
+     * @param from the habit group that should be moved
+     * @param to   the habit group that currently occupies the desired position
+     */
+    abstract fun reorder(from: HabitGroup, to: HabitGroup)
+    open fun repair() {}
+
+    /**
+     * Returns the number of habit groups in this list.
+     *
+     * @return number of habit groups
+     */
+    abstract fun size(): Int
+
+    /**
+     * Notifies the list that a certain list of habit groups has been modified.
+     *
+     * Depending on the implementation, this operation might trigger a write to
+     * disk, or do nothing at all. To make sure that the habit groups get persisted,
+     * this operation must be called.
+     *
+     * @param habitGroups the list of habit groups that have been modified.
+     */
+    abstract fun update(habitGroups: List<HabitGroup>)
+
+    /**
+     * Notifies the list that a certain habit group has been modified.
+     *
+     * See [.update] for more details.
+     *
+     * @param habitGroup the habit groups that has been modified.
+     */
+    fun update(habitGroup: HabitGroup) {
+        update(listOf(habitGroup))
+    }
+
+    /**
+     * For each habit group, point all the habits in it
+     * to the group it is contained in
+     * */
+    abstract fun attachHabitsToGroups()
+
+    /**
+     * Writes the list of habit groups to the given writer, in CSV format. There is
+     * one line for each habit group, containing the fields name, description,
+     * , and color. The color is written in HTML format (#000000).
+     *
+     * @param out the writer that will receive the result
+     * @throws IOException if write operations fail
+     */
+    @Throws(IOException::class)
+    fun writeCSV(out: Writer) {
+        val header = arrayOf(
+            "Position",
+            "Name",
+            "Question",
+            "Description",
+            "Color"
+        )
+        val csv = CSVWriter(out)
+        csv.writeNext(header, false)
+        for (hgr in this) {
+            val cols = arrayOf(
+                String.format("%03d", indexOf(hgr) + 1),
+                hgr.name,
+                hgr.question,
+                hgr.description,
+                hgr.color.toCsvColor()
+            )
+            csv.writeNext(cols, false)
+        }
+        csv.close()
+    }
+
+    abstract fun resort()
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/HabitList.kt

@@ -34,6 +34,10 @@ abstract class HabitList : Iterable<Habit> {
     @JvmField
     protected val filter: HabitMatcher
 
+    abstract var collapsed: Boolean
+
+    var groupId: Long? = null
+
     /**
      * Creates a new HabitList.
      *
@@ -65,6 +69,20 @@ abstract class HabitList : Iterable<Habit> {
     @Throws(IllegalArgumentException::class)
     abstract fun add(habit: Habit)
 
+    /**
+     * Inserts a new habit in the list at the given position.
+     *
+     * If the id of the habit is null, the list will assign it a new id, which
+     * is guaranteed to be unique in the scope of the list. If id is not null,
+     * the caller should make sure that the list does not already contain
+     * another habit with same id, otherwise a RuntimeException will be thrown.
+     *
+     * @param habit the habit to be inserted
+     * @throws IllegalArgumentException if the habit is already on the list.
+     */
+    @Throws(IllegalArgumentException::class)
+    abstract fun add(position: Int, habit: Habit)
+
     /**
      * Returns the habit with specified id.
      *
@@ -120,6 +138,13 @@ abstract class HabitList : Iterable<Habit> {
      */
     abstract fun remove(h: Habit)
 
+    /**
+     * Removes the reference to the habit from the list at the given position.
+     *
+     * Does not affect the repository or records
+     */
+    abstract fun removeAt(position: Int)
+
     /**
      * Removes all the habits from the list.
      */

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/HabitMatcher.kt

@@ -29,6 +29,15 @@ data class HabitMatcher(
         if (isReminderRequired && !habit.hasReminder()) return false
         if (!isCompletedAllowed && habit.isCompletedToday()) return false
         if (!isEnteredAllowed && habit.isEnteredToday()) return false
+        if (habit.collapsed) return false
+        return true
+    }
+
+    fun matches(habitGroup: HabitGroup): Boolean {
+        if (!isArchivedAllowed && habitGroup.isArchived) return false
+        if (isReminderRequired && !habitGroup.hasReminder()) return false
+        if (!isCompletedAllowed && habitGroup.isCompletedToday()) return false
+        if (!isEnteredAllowed && habitGroup.isEnteredToday()) return false
         return true
     }
 

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/ModelFactory.kt

@@ -20,6 +20,7 @@ package org.isoron.uhabits.core.models
 
 import org.isoron.uhabits.core.database.Repository
 import org.isoron.uhabits.core.models.sqlite.records.EntryRecord
+import org.isoron.uhabits.core.models.sqlite.records.HabitGroupRecord
 import org.isoron.uhabits.core.models.sqlite.records.HabitRecord
 
 /**
@@ -38,11 +39,23 @@ interface ModelFactory {
             computedEntries = buildComputedEntries()
         )
     }
+    fun buildHabitGroup(): HabitGroup {
+        val habits = buildHabitList()
+        val scores = buildScoreList()
+        val streaks = buildStreakList()
+        return HabitGroup(
+            habitList = habits,
+            scores = scores,
+            streaks = streaks
+        )
+    }
     fun buildComputedEntries(): EntryList
     fun buildOriginalEntries(): EntryList
     fun buildHabitList(): HabitList
+    fun buildHabitGroupList(): HabitGroupList
     fun buildScoreList(): ScoreList
     fun buildStreakList(): StreakList
     fun buildHabitListRepository(): Repository<HabitRecord>
     fun buildRepetitionListRepository(): Repository<EntryRecord>
+    fun buildHabitGroupListRepository(): Repository<HabitGroupRecord>
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/ScoreList.kt

@@ -19,8 +19,6 @@
 package org.isoron.uhabits.core.models
 
 import org.isoron.uhabits.core.models.Score.Companion.compute
-import java.util.ArrayList
-import java.util.HashMap
 import javax.annotation.concurrent.ThreadSafe
 import kotlin.math.max
 import kotlin.math.min
@@ -138,4 +136,21 @@ class ScoreList {
             map[timestamp] = Score(timestamp, previousValue)
         }
     }
+
+    @Synchronized
+    fun combineFrom(
+        habitList: HabitList,
+        from: Timestamp,
+        to: Timestamp
+    ) {
+        var current = to
+        while (current >= from) {
+            val habitScores = habitList
+                .filter { !it.isArchived }
+                .map { it.scores[current].value }
+            val averageScore = if (habitScores.isNotEmpty()) habitScores.average() else 0.0
+            map[current] = Score(current, averageScore)
+            current = current.minus(1)
+        }
+    }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/Streak.kt

@@ -38,4 +38,8 @@ data class Streak(
 
     val length: Int
         get() = start.daysUntil(end) + 1
+
+    fun isInStreak(timestamp: Timestamp): Boolean {
+        return timestamp in start..end
+    }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/StreakList.kt

@@ -62,4 +62,38 @@ class StreakList {
         }
         list.add(Streak(begin, end))
     }
+
+    @Synchronized
+    fun isInStreaks(timestamp: Timestamp): Boolean {
+        return list.any { it.isInStreak(timestamp) }
+    }
+
+    @Synchronized
+    fun combineFrom(
+        habitList: HabitList,
+        from: Timestamp,
+        to: Timestamp
+    ) {
+        list.clear()
+        if (habitList.isEmpty) return
+        var current = from
+        var streakRunning = false
+        var streakStart = from
+        val notArchivedHabits = habitList.filter { !it.isArchived }
+        while (current <= to) {
+            if (notArchivedHabits.all { it.streaks.isInStreaks(current) }) {
+                if (!streakRunning) {
+                    streakStart = current
+                    streakRunning = true
+                }
+            } else {
+                if (streakRunning) {
+                    val streakEnd = current.minus(1)
+                    list.add(Streak(streakStart, streakEnd))
+                    streakRunning = false
+                }
+            }
+            current = current.plus(1)
+        }
+    }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/memory/MemoryHabitGroupList.kt

@@ -0,0 +1,225 @@
+package org.isoron.uhabits.core.models.memory
+
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.HabitList.Order
+import org.isoron.uhabits.core.models.HabitMatcher
+import org.isoron.uhabits.core.utils.DateUtils.Companion.getTodayWithOffset
+import java.util.LinkedList
+import java.util.Objects
+
+/**
+ * In-memory implementation of [HabitGroupList].
+ */
+class MemoryHabitGroupList : HabitGroupList {
+    private val list = LinkedList<HabitGroup>()
+
+    @get:Synchronized
+    override var primaryOrder = Order.BY_POSITION
+        set(value) {
+            field = value
+            comparator = getComposedComparatorByOrder(primaryOrder, secondaryOrder)
+            resort()
+        }
+
+    @get:Synchronized
+    override var secondaryOrder = Order.BY_NAME_ASC
+        set(value) {
+            field = value
+            comparator = getComposedComparatorByOrder(primaryOrder, secondaryOrder)
+            resort()
+        }
+
+    private var comparator: Comparator<HabitGroup>? =
+        getComposedComparatorByOrder(primaryOrder, secondaryOrder)
+    private var parent: MemoryHabitGroupList? = null
+
+    constructor() : super()
+    constructor(
+        matcher: HabitMatcher,
+        comparator: Comparator<HabitGroup>?,
+        parent: MemoryHabitGroupList
+    ) : super(matcher) {
+        this.parent = parent
+        this.comparator = comparator
+        primaryOrder = parent.primaryOrder
+        secondaryOrder = parent.secondaryOrder
+        parent.observable.addListener { loadFromParent() }
+        loadFromParent()
+    }
+
+    @Synchronized
+    @Throws(IllegalArgumentException::class)
+    override fun add(habitGroup: HabitGroup) {
+        throwIfHasParent()
+        require(!list.contains(habitGroup)) { "habit already added" }
+        val id = habitGroup.id
+        if (id != null && getById(id) != null) throw RuntimeException("duplicate id")
+        if (id == null) habitGroup.id = list.size.toLong()
+        list.addLast(habitGroup)
+        resort()
+    }
+
+    @Synchronized
+    override fun getById(id: Long): HabitGroup? {
+        for (h in list) {
+            checkNotNull(h.id)
+            if (h.id == id) return h
+        }
+        return null
+    }
+
+    @Synchronized
+    override fun getByUUID(uuid: String?): HabitGroup? {
+        for (h in list) if (Objects.requireNonNull(h.uuid) == uuid) return h
+        return null
+    }
+
+    @Synchronized
+    override fun getByPosition(position: Int): HabitGroup {
+        return list[position]
+    }
+
+    @Synchronized
+    override fun getFiltered(matcher: HabitMatcher?): HabitGroupList {
+        return MemoryHabitGroupList(matcher!!, comparator, this)
+    }
+
+    private fun getComposedComparatorByOrder(
+        firstOrder: Order,
+        secondOrder: Order?
+    ): Comparator<HabitGroup> {
+        return Comparator { h1: HabitGroup, h2: HabitGroup ->
+            val firstResult = getComparatorByOrder(firstOrder).compare(h1, h2)
+            if (firstResult != 0 || secondOrder == null) {
+                return@Comparator firstResult
+            }
+            getComparatorByOrder(secondOrder).compare(h1, h2)
+        }
+    }
+
+    private fun getComparatorByOrder(order: Order): Comparator<HabitGroup> {
+        val nameComparatorAsc = Comparator<HabitGroup> { habit1, habit2 ->
+            habit1.name.compareTo(habit2.name)
+        }
+        val nameComparatorDesc =
+            Comparator { h1: HabitGroup, h2: HabitGroup -> nameComparatorAsc.compare(h2, h1) }
+        val colorComparatorAsc = Comparator<HabitGroup> { (color1), (color2) ->
+            color1.compareTo(color2)
+        }
+        val colorComparatorDesc =
+            Comparator { h1: HabitGroup, h2: HabitGroup -> colorComparatorAsc.compare(h2, h1) }
+        val scoreComparatorDesc =
+            Comparator<HabitGroup> { habit1, habit2 ->
+                val today = getTodayWithOffset()
+                habit1.scores[today].value.compareTo(habit2.scores[today].value)
+            }
+        val scoreComparatorAsc =
+            Comparator { h1: HabitGroup, h2: HabitGroup -> scoreComparatorDesc.compare(h2, h1) }
+        val positionComparator =
+            Comparator<HabitGroup> { habit1, habit2 -> habit1.position.compareTo(habit2.position) }
+        val statusComparatorDesc = Comparator { h1: HabitGroup, h2: HabitGroup ->
+            if (h1.isCompletedToday() != h2.isCompletedToday()) {
+                return@Comparator if (h1.isCompletedToday()) -1 else 1
+            }
+            val today = getTodayWithOffset()
+            val v1 = h1.scores[today].value
+            val v2 = h2.scores[today].value
+            v2.compareTo(v1)
+        }
+        val statusComparatorAsc =
+            Comparator { h1: HabitGroup, h2: HabitGroup -> statusComparatorDesc.compare(h2, h1) }
+        return when {
+            order === Order.BY_POSITION -> positionComparator
+            order === Order.BY_NAME_ASC -> nameComparatorAsc
+            order === Order.BY_NAME_DESC -> nameComparatorDesc
+            order === Order.BY_COLOR_ASC -> colorComparatorAsc
+            order === Order.BY_COLOR_DESC -> colorComparatorDesc
+            order === Order.BY_SCORE_DESC -> scoreComparatorDesc
+            order === Order.BY_SCORE_ASC -> scoreComparatorAsc
+            order === Order.BY_STATUS_DESC -> statusComparatorDesc
+            order === Order.BY_STATUS_ASC -> statusComparatorAsc
+            else -> throw IllegalStateException()
+        }
+    }
+
+    @Synchronized
+    override fun indexOf(h: HabitGroup): Int {
+        return list.indexOf(h)
+    }
+
+    @Synchronized
+    override fun iterator(): Iterator<HabitGroup> {
+        return ArrayList(list).iterator()
+    }
+
+    @Synchronized
+    override fun remove(h: HabitGroup) {
+        throwIfHasParent()
+        list.remove(h)
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun reorder(from: HabitGroup, to: HabitGroup) {
+        throwIfHasParent()
+        check(!(primaryOrder !== Order.BY_POSITION)) { "cannot reorder automatically sorted list" }
+        require(indexOf(from) >= 0) { "list does not contain (from) habit" }
+        val toPos = indexOf(to)
+        require(toPos >= 0) { "list does not contain (to) habit" }
+        list.remove(from)
+        list.add(toPos, from)
+        var position = 0
+        for (h in list) h.position = position++
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun size(): Int {
+        return list.size
+    }
+
+    @Synchronized
+    override fun update(habitGroups: List<HabitGroup>) {
+        resort()
+    }
+
+    override fun attachHabitsToGroups() {
+        for (hgr in list) {
+            for (h in hgr.habitList) {
+                h.group = hgr
+            }
+        }
+    }
+
+    private fun throwIfHasParent() {
+        check(parent == null) {
+            "Filtered lists cannot be modified directly. " +
+                "You should modify the parent list instead."
+        }
+    }
+
+    @Synchronized
+    private fun loadFromParent() {
+        checkNotNull(parent)
+        list.clear()
+        for (hgr in parent!!) {
+            if (filter.matches(hgr)) {
+                val filteredHgr = HabitGroup(hgr, filter)
+                list.add(filteredHgr)
+            }
+        }
+        primaryOrder = parent!!.primaryOrder
+        secondaryOrder = parent!!.secondaryOrder
+    }
+
+    @Synchronized
+    override fun resort() {
+        for (hgr in list) {
+            hgr.habitList.primaryOrder = primaryOrder
+            hgr.habitList.secondaryOrder = secondaryOrder
+        }
+        if (comparator != null) list.sortWith(comparator!!)
+        observable.notifyListeners()
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/memory/MemoryHabitList.kt

@@ -22,8 +22,6 @@ import org.isoron.uhabits.core.models.Habit
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.HabitMatcher
 import org.isoron.uhabits.core.utils.DateUtils.Companion.getTodayWithOffset
-import java.util.ArrayList
-import java.util.Comparator
 import java.util.LinkedList
 import java.util.Objects
 
@@ -53,6 +51,13 @@ class MemoryHabitList : HabitList {
         getComposedComparatorByOrder(primaryOrder, secondaryOrder)
     private var parent: MemoryHabitList? = null
 
+    override var collapsed: Boolean = false
+        set(value) {
+            field = value
+            val habits = parent?.list ?: list
+            habits.forEach { it.collapsed = value }
+        }
+
     constructor() : super()
     constructor(
         matcher: HabitMatcher,
@@ -61,6 +66,7 @@ class MemoryHabitList : HabitList {
     ) : super(matcher) {
         this.parent = parent
         this.comparator = comparator
+        this.groupId = parent.groupId
         primaryOrder = parent.primaryOrder
         secondaryOrder = parent.secondaryOrder
         parent.observable.addListener { loadFromParent() }
@@ -79,6 +85,17 @@ class MemoryHabitList : HabitList {
         resort()
     }
 
+    @Synchronized
+    @Throws(IllegalArgumentException::class)
+    override fun add(position: Int, habit: Habit) {
+        throwIfHasParent()
+        require(!list.contains(habit)) { "habit already added" }
+        val id = habit.id
+        if (id != null && getById(id) != null) throw RuntimeException("duplicate id")
+        if (id == null) habit.id = list.size.toLong()
+        list.add(position, habit)
+    }
+
     @Synchronized
     override fun getById(id: Long): Habit? {
         for (h in list) {
@@ -182,6 +199,13 @@ class MemoryHabitList : HabitList {
         observable.notifyListeners()
     }
 
+    @Synchronized
+    override fun removeAt(position: Int) {
+        throwIfHasParent()
+        list.removeAt(position)
+        observable.notifyListeners()
+    }
+
     @Synchronized
     override fun reorder(from: Habit, to: Habit) {
         throwIfHasParent()
@@ -218,6 +242,8 @@ class MemoryHabitList : HabitList {
         checkNotNull(parent)
         list.clear()
         for (h in parent!!) if (filter.matches(h)) list.add(h)
+        primaryOrder = parent!!.primaryOrder
+        secondaryOrder = parent!!.secondaryOrder
         resort()
     }
 

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/memory/MemoryModelFactory.kt

@@ -27,8 +27,10 @@ class MemoryModelFactory : ModelFactory {
     override fun buildComputedEntries() = EntryList()
     override fun buildOriginalEntries() = EntryList()
     override fun buildHabitList() = MemoryHabitList()
+    override fun buildHabitGroupList() = MemoryHabitGroupList()
     override fun buildScoreList() = ScoreList()
     override fun buildStreakList() = StreakList()
     override fun buildHabitListRepository() = throw NotImplementedError()
     override fun buildRepetitionListRepository() = throw NotImplementedError()
+    override fun buildHabitGroupListRepository() = throw NotImplementedError()
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/sqlite/SQLModelFactory.kt

@@ -25,6 +25,7 @@ import org.isoron.uhabits.core.models.ModelFactory
 import org.isoron.uhabits.core.models.ScoreList
 import org.isoron.uhabits.core.models.StreakList
 import org.isoron.uhabits.core.models.sqlite.records.EntryRecord
+import org.isoron.uhabits.core.models.sqlite.records.HabitGroupRecord
 import org.isoron.uhabits.core.models.sqlite.records.HabitRecord
 import javax.inject.Inject
 
@@ -38,6 +39,8 @@ class SQLModelFactory
     override fun buildOriginalEntries() = SQLiteEntryList(database)
     override fun buildComputedEntries() = EntryList()
     override fun buildHabitList() = SQLiteHabitList(this)
+    override fun buildHabitGroupList() = SQLiteHabitGroupList(this)
+
     override fun buildScoreList() = ScoreList()
     override fun buildStreakList() = StreakList()
 
@@ -46,4 +49,7 @@ class SQLModelFactory
 
     override fun buildRepetitionListRepository() =
         Repository(EntryRecord::class.java, database)
+
+    override fun buildHabitGroupListRepository() =
+        Repository(HabitGroupRecord::class.java, database)
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/sqlite/SQLiteEntryList.kt

@@ -81,12 +81,4 @@ class SQLiteEntryList(database: Database) : EntryList() {
     override fun recomputeFrom(originalEntries: EntryList, frequency: Frequency, isNumerical: Boolean) {
         throw UnsupportedOperationException()
     }
-
-    override fun clear() {
-        super.clear()
-        repository.execSQL(
-            "delete from repetitions where habit = ?",
-            habitId.toString()
-        )
-    }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/sqlite/SQLiteHabitGroupList.kt

@@ -0,0 +1,205 @@
+package org.isoron.uhabits.core.models.sqlite
+
+import org.isoron.uhabits.core.database.Repository
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.HabitList.Order
+import org.isoron.uhabits.core.models.HabitMatcher
+import org.isoron.uhabits.core.models.ModelFactory
+import org.isoron.uhabits.core.models.memory.MemoryHabitGroupList
+import org.isoron.uhabits.core.models.sqlite.records.HabitGroupRecord
+import javax.inject.Inject
+
+/**
+ * Implementation of a [HabitGroupList] that is backed by SQLite.
+ */
+class SQLiteHabitGroupList @Inject constructor(private val modelFactory: ModelFactory) : HabitGroupList() {
+    private val repository: Repository<HabitGroupRecord> = modelFactory.buildHabitGroupListRepository()
+    private val list: MemoryHabitGroupList = MemoryHabitGroupList()
+    private var loaded = false
+    private fun loadRecords() {
+        if (loaded) return
+        loaded = true
+        list.removeAll()
+        val records = repository.findAll("order by position")
+        var shouldRebuildOrder = false
+        for ((expectedPosition, rec) in records.withIndex()) {
+            if (rec.position != expectedPosition) shouldRebuildOrder = true
+            val h = modelFactory.buildHabitGroup()
+            rec.copyTo(h)
+            list.add(h)
+        }
+        if (shouldRebuildOrder) rebuildOrder()
+    }
+
+    @Synchronized
+    override fun add(habitGroup: HabitGroup) {
+        loadRecords()
+        habitGroup.position = size()
+        habitGroup.id = repository.getNextAvailableId("habitandgroup")
+        val record = HabitGroupRecord()
+        record.copyFrom(habitGroup)
+        repository.save(record)
+        habitGroup.habitList.groupId = record.id
+        list.add(habitGroup)
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun getById(id: Long): HabitGroup? {
+        loadRecords()
+        return list.getById(id)
+    }
+
+    @Synchronized
+    override fun getByUUID(uuid: String?): HabitGroup? {
+        loadRecords()
+        return list.getByUUID(uuid)
+    }
+
+    @Synchronized
+    override fun getByPosition(position: Int): HabitGroup {
+        loadRecords()
+        return list.getByPosition(position)
+    }
+
+    @Synchronized
+    override fun getFiltered(matcher: HabitMatcher?): HabitGroupList {
+        loadRecords()
+        return list.getFiltered(matcher)
+    }
+
+    @set:Synchronized
+    override var primaryOrder: Order
+        get() = list.primaryOrder
+        set(order) {
+            list.primaryOrder = order
+            observable.notifyListeners()
+        }
+
+    @set:Synchronized
+    override var secondaryOrder: Order
+        get() = list.secondaryOrder
+        set(order) {
+            list.secondaryOrder = order
+            observable.notifyListeners()
+        }
+
+    @Synchronized
+    override fun indexOf(h: HabitGroup): Int {
+        loadRecords()
+        return list.indexOf(h)
+    }
+
+    @Synchronized
+    override fun iterator(): Iterator<HabitGroup> {
+        loadRecords()
+        return list.iterator()
+    }
+
+    @Synchronized
+    private fun rebuildOrder() {
+        val records = repository.findAll("order by position")
+        repository.executeAsTransaction {
+            for ((pos, r) in records.withIndex()) {
+                if (r.position != pos) {
+                    r.position = pos
+                    repository.save(r)
+                }
+            }
+        }
+    }
+
+    @Synchronized
+    override fun remove(h: HabitGroup) {
+        loadRecords()
+        list.remove(h)
+        val record = repository.find(
+            h.id!!
+        ) ?: throw RuntimeException("habit not in database")
+        repository.executeAsTransaction {
+            repository.remove(record)
+        }
+        rebuildOrder()
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun removeAll() {
+        list.removeAll()
+        repository.execSQL("delete from habits")
+        repository.execSQL("delete from repetitions")
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun reorder(from: HabitGroup, to: HabitGroup) {
+        loadRecords()
+        list.reorder(from, to)
+        val fromRecord = repository.find(
+            from.id!!
+        )
+        val toRecord = repository.find(
+            to.id!!
+        )
+        if (fromRecord == null) throw RuntimeException("habit not in database")
+        if (toRecord == null) throw RuntimeException("habit not in database")
+        if (toRecord.position!! < fromRecord.position!!) {
+            repository.execSQL(
+                "update habitgroups set position = position + 1 " +
+                    "where position >= ? and position < ?",
+                toRecord.position!!,
+                fromRecord.position!!
+            )
+        } else {
+            repository.execSQL(
+                "update habitgroups set position = position - 1 " +
+                    "where position > ? and position <= ?",
+                fromRecord.position!!,
+                toRecord.position!!
+            )
+        }
+        fromRecord.position = toRecord.position
+        repository.save(fromRecord)
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun repair() {
+        loadRecords()
+        rebuildOrder()
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    override fun size(): Int {
+        loadRecords()
+        return list.size()
+    }
+
+    @Synchronized
+    override fun update(habitGroups: List<HabitGroup>) {
+        loadRecords()
+        list.update(habitGroups)
+        for (h in habitGroups) {
+            val record = repository.find(h.id!!) ?: continue
+            record.copyFrom(h)
+            repository.save(record)
+        }
+        observable.notifyListeners()
+    }
+
+    override fun attachHabitsToGroups() {
+        list.attachHabitsToGroups()
+    }
+
+    override fun resort() {
+        list.resort()
+        observable.notifyListeners()
+    }
+
+    @Synchronized
+    fun reload() {
+        loaded = false
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/sqlite/SQLiteHabitList.kt

@@ -37,15 +37,23 @@ class SQLiteHabitList @Inject constructor(private val modelFactory: ModelFactory
     private fun loadRecords() {
         if (loaded) return
         loaded = true
+        list.groupId = this.groupId
         list.removeAll()
-        val records = repository.findAll("order by position")
+        val records = repository.findAll("order by group_id, position")
         var shouldRebuildOrder = false
-        for ((expectedPosition, rec) in records.withIndex()) {
+        var currentGroup: Long? = null
+        var expectedPosition = 0
+        for (rec in records) {
+            if (currentGroup != rec.groupId) {
+                currentGroup = rec.groupId
+                expectedPosition = 0
+            }
             if (rec.position != expectedPosition) shouldRebuildOrder = true
             val h = modelFactory.buildHabit()
             rec.copyTo(h)
             (h.originalEntries as SQLiteEntryList).habitId = h.id
-            list.add(h)
+            if (h.groupId == list.groupId) list.add(h)
+            expectedPosition++
         }
         if (shouldRebuildOrder) rebuildOrder()
     }
@@ -54,15 +62,48 @@ class SQLiteHabitList @Inject constructor(private val modelFactory: ModelFactory
     override fun add(habit: Habit) {
         loadRecords()
         habit.position = size()
+        habit.id = repository.getNextAvailableId("habitandgroup")
         val record = HabitRecord()
         record.copyFrom(habit)
         repository.save(record)
-        habit.id = record.id
         (habit.originalEntries as SQLiteEntryList).habitId = record.id
         list.add(habit)
         observable.notifyListeners()
     }
 
+    @Synchronized
+    private fun rebuildOrder() {
+        val records = repository.findAll("order by group_id, position")
+        repository.executeAsTransaction {
+            var currentGroup: Long? = null
+            var expectedPosition = 0
+            for (r in records) {
+                if (currentGroup != r.groupId) {
+                    currentGroup = r.groupId
+                    expectedPosition = 0
+                }
+                if (r.position != expectedPosition) {
+                    r.position = expectedPosition
+                    repository.save(r)
+                }
+                expectedPosition++
+            }
+        }
+    }
+
+    @Synchronized
+    override fun add(position: Int, habit: Habit) {
+        loadRecords()
+        habit.position = size()
+        val record = HabitRecord()
+        record.copyFrom(habit)
+        repository.save(record)
+        habit.id = record.id
+        (habit.originalEntries as SQLiteEntryList).habitId = record.id
+        list.add(position, habit)
+        observable.notifyListeners()
+    }
+
     @Synchronized
     override fun getById(id: Long): Habit? {
         loadRecords()
@@ -103,6 +144,12 @@ class SQLiteHabitList @Inject constructor(private val modelFactory: ModelFactory
             observable.notifyListeners()
         }
 
+    override var collapsed: Boolean = list.collapsed
+        set(value) {
+            field = value
+            list.collapsed = value
+        }
+
     @Synchronized
     override fun indexOf(h: Habit): Int {
         loadRecords()
@@ -115,19 +162,6 @@ class SQLiteHabitList @Inject constructor(private val modelFactory: ModelFactory
         return list.iterator()
     }
 
-    @Synchronized
-    private fun rebuildOrder() {
-        val records = repository.findAll("order by position")
-        repository.executeAsTransaction {
-            for ((pos, r) in records.withIndex()) {
-                if (r.position != pos) {
-                    r.position = pos
-                    repository.save(r)
-                }
-            }
-        }
-    }
-
     @Synchronized
     override fun remove(h: Habit) {
         loadRecords()
@@ -143,6 +177,12 @@ class SQLiteHabitList @Inject constructor(private val modelFactory: ModelFactory
         observable.notifyListeners()
     }
 
+    @Synchronized
+    override fun removeAt(position: Int) {
+        loadRecords()
+        list.removeAt(position)
+    }
+
     @Synchronized
     override fun removeAll() {
         list.removeAll()

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/sqlite/records/HabitGroupRecord.kt

@@ -0,0 +1,91 @@
+package org.isoron.uhabits.core.models.sqlite.records
+
+import org.isoron.uhabits.core.database.Column
+import org.isoron.uhabits.core.database.Table
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.PaletteColor
+import org.isoron.uhabits.core.models.Reminder
+import org.isoron.uhabits.core.models.WeekdayList
+import java.util.Objects.requireNonNull
+
+/**
+ * The SQLite database record corresponding to a [HabitGroup].
+ */
+@Table(name = "habitgroups")
+class HabitGroupRecord {
+    @field:Column
+    var description: String? = null
+
+    @field:Column
+    var question: String? = null
+
+    @field:Column
+    var name: String? = null
+
+    @field:Column
+    var color: Int? = null
+
+    @field:Column
+    var position: Int? = null
+
+    @field:Column(name = "reminder_hour")
+    var reminderHour: Int? = null
+
+    @field:Column(name = "reminder_min")
+    var reminderMin: Int? = null
+
+    @field:Column(name = "reminder_days")
+    var reminderDays: Int? = null
+
+    @field:Column
+    var highlight: Int? = null
+
+    @field:Column
+    var archived: Int? = null
+
+    @field:Column
+    var id: Long? = null
+
+    @field:Column
+    var uuid: String? = null
+
+    fun copyFrom(model: HabitGroup) {
+        id = model.id
+        name = model.name
+        description = model.description
+        highlight = 0
+        color = model.color.paletteIndex
+        archived = if (model.isArchived) 1 else 0
+        position = model.position
+        question = model.question
+        uuid = model.uuid
+        reminderDays = 0
+        reminderMin = null
+        reminderHour = null
+        if (model.hasReminder()) {
+            val reminder = model.reminder
+            reminderHour = requireNonNull(reminder)!!.hour
+            reminderMin = reminder!!.minute
+            reminderDays = reminder.days.toInteger()
+        }
+    }
+
+    fun copyTo(habitGroup: HabitGroup) {
+        habitGroup.id = id
+        habitGroup.name = name!!
+        habitGroup.description = description!!
+        habitGroup.question = question!!
+        habitGroup.color = PaletteColor(color!!)
+        habitGroup.isArchived = archived != 0
+        habitGroup.position = position!!
+        habitGroup.uuid = uuid
+        habitGroup.habitList.groupId = id
+        if (reminderHour != null && reminderMin != null) {
+            habitGroup.reminder = Reminder(
+                reminderHour!!,
+                reminderMin!!,
+                WeekdayList(reminderDays!!)
+            )
+        }
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/models/sqlite/records/HabitRecord.kt

@@ -88,6 +88,12 @@ class HabitRecord {
     @field:Column
     var uuid: String? = null
 
+    @field:Column(name = "group_id")
+    var groupId: Long? = null
+
+    @field:Column(name = "group_uuid")
+    var groupUUID: String? = null
+
     fun copyFrom(model: Habit) {
         id = model.id
         name = model.name
@@ -102,6 +108,8 @@ class HabitRecord {
         position = model.position
         question = model.question
         uuid = model.uuid
+        groupId = model.groupId
+        groupUUID = model.groupUUID
         val (numerator, denominator) = model.frequency
         freqNum = numerator
         freqDen = denominator
@@ -130,6 +138,8 @@ class HabitRecord {
         habit.unit = unit!!
         habit.position = position!!
         habit.uuid = uuid
+        habit.groupId = groupId
+        habit.groupUUID = groupUUID
         if (reminderHour != null && reminderMin != null) {
             habit.reminder = Reminder(
                 reminderHour!!,

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/reminders/ReminderScheduler.kt

@@ -24,6 +24,8 @@ import org.isoron.uhabits.core.commands.Command
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateRepetitionCommand
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.HabitMatcher
 import org.isoron.uhabits.core.preferences.WidgetPreferences
@@ -39,6 +41,7 @@ import javax.inject.Inject
 class ReminderScheduler @Inject constructor(
     private val commandRunner: CommandRunner,
     private val habitList: HabitList,
+    private val habitGroupList: HabitGroupList,
     private val sys: SystemScheduler,
     private val widgetPreferences: WidgetPreferences
 ) : CommandRunner.Listener {
@@ -83,6 +86,40 @@ class ReminderScheduler @Inject constructor(
         scheduleAtTime(habit, reminderTime)
     }
 
+    @Synchronized
+    fun schedule(habitGroup: HabitGroup) {
+        if (habitGroup.id == null) {
+            sys.log("ReminderScheduler", "Habit group has null id. Returning.")
+            return
+        }
+        if (!habitGroup.hasReminder()) {
+            sys.log("ReminderScheduler", "habit group=" + habitGroup.id + " has no reminder. Skipping.")
+            return
+        }
+        var reminderTime = Objects.requireNonNull(habitGroup.reminder)!!.timeInMillis
+        val snoozeReminderTime = widgetPreferences.getSnoozeTime(habitGroup.id!!)
+        if (snoozeReminderTime != 0L) {
+            val now = applyTimezone(getLocalTime())
+            sys.log(
+                "ReminderScheduler",
+                String.format(
+                    Locale.US,
+                    "Habit group %d has been snoozed until %d",
+                    habitGroup.id,
+                    snoozeReminderTime
+                )
+            )
+            if (snoozeReminderTime > now) {
+                sys.log("ReminderScheduler", "Snooze time is in the future. Accepting.")
+                reminderTime = snoozeReminderTime
+            } else {
+                sys.log("ReminderScheduler", "Snooze time is in the past. Discarding.")
+                widgetPreferences.removeSnoozeTime(habitGroup.id!!)
+            }
+        }
+        scheduleAtTime(habitGroup, reminderTime)
+    }
+
     @Synchronized
     fun scheduleAtTime(habit: Habit, reminderTime: Long) {
         sys.log("ReminderScheduler", "Scheduling alarm for habit=" + habit.id)
@@ -108,16 +145,48 @@ class ReminderScheduler @Inject constructor(
         sys.scheduleShowReminder(reminderTime, habit, timestamp)
     }
 
+    @Synchronized
+    fun scheduleAtTime(habitGroup: HabitGroup, reminderTime: Long) {
+        sys.log("ReminderScheduler", "Scheduling alarm for habit group=" + habitGroup.id)
+        if (!habitGroup.hasReminder()) {
+            sys.log("ReminderScheduler", "habit group=" + habitGroup.id + " has no reminder. Skipping.")
+            return
+        }
+        if (habitGroup.isArchived) {
+            sys.log("ReminderScheduler", "habit group=" + habitGroup.id + " is archived. Skipping.")
+            return
+        }
+        val timestamp = getStartOfDayWithOffset(removeTimezone(reminderTime))
+        sys.log(
+            "ReminderScheduler",
+            String.format(
+                Locale.US,
+                "reminderTime=%d removeTimezone=%d timestamp=%d",
+                reminderTime,
+                removeTimezone(reminderTime),
+                timestamp
+            )
+        )
+        sys.scheduleShowReminder(reminderTime, habitGroup, timestamp)
+    }
+
     @Synchronized
     fun scheduleAll() {
         sys.log("ReminderScheduler", "Scheduling all alarms")
         val reminderHabits = habitList.getFiltered(HabitMatcher.WITH_ALARM)
+        val reminderSubHabits = habitGroupList.map { it.habitList.getFiltered(HabitMatcher.WITH_ALARM) }.flatten()
+        val reminderHabitGroups = habitGroupList.getFiltered(HabitMatcher.WITH_ALARM)
         for (habit in reminderHabits) schedule(habit)
+        for (habit in reminderSubHabits) schedule(habit)
+        for (hgr in reminderHabitGroups) schedule(hgr)
     }
 
     @Synchronized
     fun hasHabitsWithReminders(): Boolean {
-        return !habitList.getFiltered(HabitMatcher.WITH_ALARM).isEmpty
+        if (!habitList.getFiltered(HabitMatcher.WITH_ALARM).isEmpty) return true
+        if (habitGroupList.map { it.habitList.getFiltered(HabitMatcher.WITH_ALARM) }.flatten().isNotEmpty()) return true
+        if (!habitGroupList.getFiltered(HabitMatcher.WITH_ALARM).isEmpty) return true
+        return false
     }
 
     @Synchronized
@@ -138,6 +207,14 @@ class ReminderScheduler @Inject constructor(
         schedule(habit)
     }
 
+    @Synchronized
+    fun snoozeReminder(habitGroup: HabitGroup, minutes: Long) {
+        val now = applyTimezone(getLocalTime())
+        val snoozedUntil = now + minutes * 60 * 1000
+        widgetPreferences.setSnoozeTime(habitGroup.id!!, snoozedUntil)
+        schedule(habitGroup)
+    }
+
     interface SystemScheduler {
         fun scheduleShowReminder(
             reminderTime: Long,
@@ -145,6 +222,12 @@ class ReminderScheduler @Inject constructor(
             timestamp: Long
         ): SchedulerResult
 
+        fun scheduleShowReminder(
+            reminderTime: Long,
+            habitGroup: HabitGroup,
+            timestamp: Long
+        ): SchedulerResult
+
         fun scheduleWidgetUpdate(updateTime: Long): SchedulerResult?
         fun log(componentName: String, msg: String)
     }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/test/HabitGroupFixtures.kt

@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.isoron.uhabits.core.test
+
+import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.models.HabitList
+import org.isoron.uhabits.core.models.ModelFactory
+import org.isoron.uhabits.core.models.NumericalHabitType
+import org.isoron.uhabits.core.models.PaletteColor
+import org.isoron.uhabits.core.models.sqlite.SQLiteHabitList
+
+class HabitGroupFixtures(private val modelFactory: ModelFactory, private val habitList: HabitList, private val habitGroupList: HabitGroupList) {
+    private val habitFixtures = HabitFixtures(modelFactory, habitList)
+
+    fun createEmptyHabitGroup(
+        name: String = "Exercise",
+        color: PaletteColor = PaletteColor(3),
+        position: Int = 0,
+        id: Long = 0L
+    ): HabitGroup {
+        val hgr = modelFactory.buildHabitGroup()
+        hgr.name = name
+        hgr.id = id
+        hgr.question = "Did you exercise today?"
+        hgr.color = color
+        hgr.position = position
+        saveIfSQLite(hgr)
+        return hgr
+    }
+
+    fun createGroupWithEmptyHabits(
+        name: String = "Exercise",
+        color: PaletteColor = PaletteColor(3),
+        position: Int = 0,
+        numHabits: Int = 1,
+        id: Long = 0L
+    ): HabitGroup {
+        val hgr = createEmptyHabitGroup(name, color, position, id)
+        for (i in 1..numHabits) {
+            val h = habitFixtures.createEmptyHabit()
+            h.id = id + i
+            addGroupId(h, hgr)
+            hgr.habitList.add(h)
+        }
+        saveIfSQLite(hgr)
+        return hgr
+    }
+
+    fun createGroupWithEmptyNumericalHabits(
+        name: String = "Exercise",
+        color: PaletteColor = PaletteColor(3),
+        position: Int = 0,
+        targetType: NumericalHabitType = NumericalHabitType.AT_LEAST,
+        numHabits: Int = 1,
+        id: Long = 0L
+    ): HabitGroup {
+        val hgr = createEmptyHabitGroup(name, color, position, id)
+        for (i in 1..numHabits) {
+            val h = habitFixtures.createEmptyNumericalHabit(targetType)
+            h.id = id + i
+            addGroupId(h, hgr)
+            hgr.habitList.add(h)
+        }
+        saveIfSQLite(hgr)
+        return hgr
+    }
+
+    fun createGroupWithNumericalHabits(
+        name: String = "Exercise",
+        color: PaletteColor = PaletteColor(3),
+        position: Int = 0,
+        numHabits: Int = 1,
+        id: Long = 0L
+    ): HabitGroup {
+        val hgr = createEmptyHabitGroup(name, color, position, id)
+        for (i in 1..numHabits) {
+            val h = habitFixtures.createNumericalHabit()
+            h.id = id + i
+            addGroupId(h, hgr)
+            hgr.habitList.add(h)
+        }
+        saveIfSQLite(hgr)
+        return hgr
+    }
+
+    fun createGroupWithLongHabits(
+        name: String = "Exercise",
+        color: PaletteColor = PaletteColor(3),
+        position: Int = 0,
+        numHabits: Int = 1,
+        id: Long = 0L
+    ): HabitGroup {
+        val hgr = createEmptyHabitGroup(name, color, position, id)
+        for (i in 1..numHabits) {
+            val h = habitFixtures.createLongHabit()
+            h.id = id + i
+            addGroupId(h, hgr)
+            hgr.habitList.add(h)
+        }
+        saveIfSQLite(hgr)
+        return hgr
+    }
+
+    fun createGroupWithShortHabits(
+        name: String = "Exercise",
+        color: PaletteColor = PaletteColor(3),
+        position: Int = 0,
+        numHabits: Int = 1,
+        id: Long = 0L
+    ): HabitGroup {
+        val hgr = createEmptyHabitGroup(name, color, position, id)
+        for (i in 1..numHabits) {
+            val h = habitFixtures.createShortHabit()
+            h.id = id + i
+            addGroupId(h, hgr)
+            hgr.habitList.add(h)
+        }
+        saveIfSQLite(hgr)
+        return hgr
+    }
+
+    private fun saveIfSQLite(hgr: HabitGroup) {
+        if (hgr.habitList !is SQLiteHabitList) return
+        habitGroupList.add(hgr)
+    }
+
+    private fun addGroupId(h: Habit, hgr: HabitGroup) {
+        h.groupId = hgr.id
+        h.group = hgr
+        h.groupUUID = hgr.uuid
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/NotificationTray.kt

@@ -22,13 +22,14 @@ import org.isoron.uhabits.core.AppScope
 import org.isoron.uhabits.core.commands.Command
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateRepetitionCommand
+import org.isoron.uhabits.core.commands.DeleteHabitGroupsCommand
 import org.isoron.uhabits.core.commands.DeleteHabitsCommand
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.preferences.Preferences
 import org.isoron.uhabits.core.tasks.Task
 import org.isoron.uhabits.core.tasks.TaskRunner
-import java.util.HashMap
 import java.util.Locale
 import java.util.Objects
 import javax.inject.Inject
@@ -40,11 +41,18 @@ class NotificationTray @Inject constructor(
     private val preferences: Preferences,
     private val systemTray: SystemTray
 ) : CommandRunner.Listener, Preferences.Listener {
-    private val active: HashMap<Habit, NotificationData> = HashMap()
+    private val activeHabits: HashMap<Habit, NotificationData> = HashMap()
+    private val activeHabitGroups: HashMap<HabitGroup, NotificationData> = HashMap()
     fun cancel(habit: Habit) {
         val notificationId = getNotificationId(habit)
         systemTray.removeNotification(notificationId)
-        active.remove(habit)
+        activeHabits.remove(habit)
+    }
+
+    fun cancel(habitGroup: HabitGroup) {
+        val notificationId = getNotificationId(habitGroup)
+        systemTray.removeNotification(notificationId)
+        activeHabitGroups.remove(habitGroup)
     }
 
     override fun onCommandFinished(command: Command) {
@@ -56,6 +64,13 @@ class NotificationTray @Inject constructor(
             val (_, deleted) = command
             for (habit in deleted) cancel(habit)
         }
+        if (command is DeleteHabitGroupsCommand) {
+            val (_, deletedGroups) = command
+            for (hgr in deletedGroups) {
+                for (h in hgr.habitList) cancel(h)
+                cancel(hgr)
+            }
+        }
     }
 
     override fun onNotificationsChanged() {
@@ -64,10 +79,16 @@ class NotificationTray @Inject constructor(
 
     fun show(habit: Habit, timestamp: Timestamp, reminderTime: Long) {
         val data = NotificationData(timestamp, reminderTime)
-        active[habit] = data
+        activeHabits[habit] = data
         taskRunner.execute(ShowNotificationTask(habit, data))
     }
 
+    fun show(habitGroup: HabitGroup, timestamp: Timestamp, reminderTime: Long) {
+        val data = NotificationData(timestamp, reminderTime)
+        activeHabitGroups[habitGroup] = data
+        taskRunner.execute(ShowNotificationTask(habitGroup, data))
+    }
+
     fun startListening() {
         commandRunner.addListener(this)
         preferences.addListener(this)
@@ -83,18 +104,32 @@ class NotificationTray @Inject constructor(
         return (id % Int.MAX_VALUE).toInt()
     }
 
+    private fun getNotificationId(habitGroup: HabitGroup): Int {
+        val id = habitGroup.id ?: return 0
+        return (id % Int.MAX_VALUE).toInt()
+    }
+
     private fun reshowAll() {
-        for ((habit, data) in active.entries) {
+        for ((habit, data) in activeHabits.entries) {
             taskRunner.execute(ShowNotificationTask(habit, data))
         }
+        for ((habitGroup, data) in activeHabitGroups.entries) {
+            taskRunner.execute(ShowNotificationTask(habitGroup, data))
+        }
     }
 
     fun reshow(habit: Habit) {
-        active[habit]?.let {
+        activeHabits[habit]?.let {
             taskRunner.execute(ShowNotificationTask(habit, it))
         }
     }
 
+    fun reshow(habitGroup: HabitGroup) {
+        activeHabitGroups[habitGroup]?.let {
+            taskRunner.execute(ShowNotificationTask(habitGroup, it))
+        }
+    }
+
     interface SystemTray {
         fun removeNotification(notificationId: Int)
         fun showNotification(
@@ -104,48 +139,79 @@ class NotificationTray @Inject constructor(
             reminderTime: Long
         )
 
+        fun showNotification(
+            habitGroup: HabitGroup,
+            notificationId: Int,
+            timestamp: Timestamp,
+            reminderTime: Long
+        )
+
         fun log(msg: String)
     }
 
     internal class NotificationData(val timestamp: Timestamp, val reminderTime: Long)
-    private inner class ShowNotificationTask(private val habit: Habit, data: NotificationData) :
+    private inner class ShowNotificationTask private constructor(
-        Task {
+        private val habit: Habit? = null,
+        private val habitGroup: HabitGroup? = null,
+        data: NotificationData
+    ) : Task {
+        // Secondary constructor for Habit
+        constructor(habit: Habit, data: NotificationData) : this(habit, null, data)
+
+        // Secondary constructor for HabitGroup
+        constructor(habitGroup: HabitGroup, data: NotificationData) : this(null, habitGroup, data)
+
         var isCompleted = false
         private val timestamp: Timestamp = data.timestamp
         private val reminderTime: Long = data.reminderTime
 
+        private val type = if (habit != null) "habit" else "habitgroup"
+        private val id = habit?.id ?: habitGroup?.id
+        private val hasReminder = habit?.hasReminder() ?: habitGroup!!.hasReminder()
+        private val isArchived = habit?.isArchived ?: habitGroup!!.isArchived
+
         override fun doInBackground() {
-            isCompleted = habit.isCompletedToday()
+            isCompleted = habit?.isCompletedToday() ?: habitGroup!!.isCompletedToday()
         }
 
         override fun onPostExecute() {
-            systemTray.log("Showing notification for habit=" + habit.id)
+            systemTray.log(
+                String.format(
+                    Locale.US,
+                    "Showing notification for %s=%d",
+                    type,
+                    id
+                )
+            )
             if (isCompleted) {
                 systemTray.log(
                     String.format(
                         Locale.US,
-                        "Habit %d already checked. Skipping.",
+                        "%s %d already checked. Skipping.",
-                        habit.id
+                        type,
+                        id
                     )
                 )
                 return
             }
-            if (!habit.hasReminder()) {
+            if (!hasReminder) {
                 systemTray.log(
                     String.format(
                         Locale.US,
-                        "Habit %d does not have a reminder. Skipping.",
+                        "%s %d does not have a reminder. Skipping.",
-                        habit.id
+                        type,
+                        id
                     )
                 )
                 return
             }
-            if (habit.isArchived) {
+            if (isArchived) {
                 systemTray.log(
                     String.format(
                         Locale.US,
-                        "Habit %d is archived. Skipping.",
+                        "%s %d is archived. Skipping.",
-                        habit.id
+                        type,
+                        id
                     )
                 )
                 return
@@ -154,23 +220,33 @@ class NotificationTray @Inject constructor(
                 systemTray.log(
                     String.format(
                         Locale.US,
-                        "Habit %d not supposed to run today. Skipping.",
+                        "%s %d not supposed to run today. Skipping.",
-                        habit.id
+                        type,
+                        id
                     )
                 )
                 return
             }
-            systemTray.showNotification(
+            if (habit != null) {
-                habit,
+                systemTray.showNotification(
-                getNotificationId(habit),
+                    habit,
-                timestamp,
+                    getNotificationId(habit),
-                reminderTime
+                    timestamp,
-            )
+                    reminderTime
+                )
+            } else {
+                systemTray.showNotification(
+                    habitGroup!!,
+                    getNotificationId(habitGroup),
+                    timestamp,
+                    reminderTime
+                )
+            }
         }
 
         private fun shouldShowReminderToday(): Boolean {
-            if (!habit.hasReminder()) return false
+            if (!hasReminder) return false
-            val reminder = habit.reminder
+            val reminder = habit?.reminder ?: habitGroup!!.reminder
             val reminderDays = Objects.requireNonNull(reminder)!!.days.toArray()
             val weekday = timestamp.weekday
             return reminderDays[weekday]

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/list/HabitCardListCache.kt

@@ -25,15 +25,15 @@ import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateRepetitionCommand
 import org.isoron.uhabits.core.io.Logging
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.HabitList.Order
 import org.isoron.uhabits.core.models.HabitMatcher
 import org.isoron.uhabits.core.tasks.Task
 import org.isoron.uhabits.core.tasks.TaskRunner
 import org.isoron.uhabits.core.utils.DateUtils.Companion.getTodayWithOffset
-import java.util.ArrayList
 import java.util.Arrays
-import java.util.HashMap
 import java.util.LinkedList
 import java.util.TreeSet
 import javax.inject.Inject
@@ -53,7 +53,8 @@ import javax.inject.Inject
  */
 @AppScope
 class HabitCardListCache @Inject constructor(
-    private val allHabits: HabitList,
+    private val habits: HabitList,
+    private val habitGroups: HabitGroupList,
     private val commandRunner: CommandRunner,
     taskRunner: TaskRunner,
     logging: Logging
@@ -66,6 +67,7 @@ class HabitCardListCache @Inject constructor(
     private var listener: Listener
     private val data: CacheData
     private var filteredHabits: HabitList
+    private var filteredHabitGroups: HabitGroupList
     private val taskRunner: TaskRunner
 
     @Synchronized
@@ -74,42 +76,86 @@ class HabitCardListCache @Inject constructor(
     }
 
     @Synchronized
-    fun getCheckmarks(habitId: Long): IntArray {
+    fun getCheckmarks(habitID: Long): IntArray {
-        return data.checkmarks[habitId]!!
+        return data.checkmarks[habitID]!!
     }
 
     @Synchronized
-    fun getNotes(habitId: Long): Array<String> {
+    fun getNotes(habitID: Long): Array<String> {
-        return data.notes[habitId]!!
+        return data.notes[habitID]!!
     }
 
     @Synchronized
     fun hasNoHabit(): Boolean {
-        return allHabits.isEmpty
+        return habits.isEmpty
+    }
+
+    @Synchronized
+    fun hasNoHabitGroup(): Boolean {
+        return habitGroups.isEmpty
+    }
+
+    @Synchronized
+    fun hasNoSubHabits(): Boolean {
+        return habitGroups.all { it.habitList.isEmpty }
     }
 
     /**
      * Returns the habits that occupies a certain position on the list.
      *
-     * @param position the position of the habit
+     * @param position the position of the list of habits and groups
      * @return the habit at given position or null if position is invalid
      */
     @Synchronized
     fun getHabitByPosition(position: Int): Habit? {
-        return if (position < 0 || position >= data.habits.size) null else data.habits[position]
+        return data.positionToHabit[position]
+    }
+
+    /**
+     * Returns the habit groups that occupies a certain position on the list.
+     *
+     * @param position the position of the list of habits and groups
+     * @return the habit group at given position or null if position is invalid
+     */
+    @Synchronized
+    fun getHabitGroupByPosition(position: Int): HabitGroup? {
+        return data.positionToHabitGroup[position]
+    }
+
+    @Synchronized
+    fun getIdByPosition(position: Int): Long? {
+        return if (data.positionTypes[position] == STANDALONE_HABIT || data.positionTypes[position] == SUB_HABIT) {
+            data.positionToHabit[position]!!.id
+        } else {
+            data.positionToHabitGroup[position]!!.id
+        }
     }
 
+    @get:Synchronized
+    val itemCount: Int
+        get() = habitCount + habitGroupCount + subHabitCount
+
     @get:Synchronized
     val habitCount: Int
         get() = data.habits.size
 
+    @get:Synchronized
+    val habitGroupCount: Int
+        get() = data.habitGroups.size
+
+    @get:Synchronized
+    val subHabitCount: Int
+        get() = data.subHabits.sumOf { it.size }
+
     @get:Synchronized
     @set:Synchronized
     var primaryOrder: Order
         get() = filteredHabits.primaryOrder
         set(order) {
-            allHabits.primaryOrder = order
+            habits.primaryOrder = order
+            habitGroups.primaryOrder = order
             filteredHabits.primaryOrder = order
+            filteredHabitGroups.primaryOrder = order
             refreshAllHabits()
         }
 
@@ -118,14 +164,16 @@ class HabitCardListCache @Inject constructor(
     var secondaryOrder: Order
         get() = filteredHabits.secondaryOrder
         set(order) {
-            allHabits.secondaryOrder = order
+            habits.secondaryOrder = order
+            habitGroups.secondaryOrder = order
             filteredHabits.secondaryOrder = order
+            filteredHabitGroups.secondaryOrder = order
             refreshAllHabits()
         }
 
     @Synchronized
-    fun getScore(habitId: Long): Double {
+    fun getScore(id: Long): Double {
-        return data.scores[habitId]!!
+        return data.scores[id]!!
     }
 
     @Synchronized
@@ -163,22 +211,59 @@ class HabitCardListCache @Inject constructor(
 
     @Synchronized
     fun remove(id: Long) {
-        val h = data.idToHabit[id] ?: return
+        val position = data.idToPosition[id] ?: return
-        val position = data.habits.indexOf(h)
+        val type = data.positionTypes[position]
-        data.habits.removeAt(position)
+        if (type == STANDALONE_HABIT) {
-        data.idToHabit.remove(id)
+            val h = data.idToHabit[id]
-        data.checkmarks.remove(id)
+            if (h != null) {
-        data.notes.remove(id)
+                data.habits.removeAt(position)
-        data.scores.remove(id)
+                data.removeWithID(id)
-        listener.onItemRemoved(position)
+                data.removeWithPos(position)
+                data.decrementPositions(position + 1, data.positionTypes.size)
+                listener.onItemRemoved(position)
+            }
+        } else if (type == SUB_HABIT) {
+            val h = data.idToHabit[id]
+            if (h != null) {
+                val hgrID = h.groupId
+                val hgr = data.idToHabitGroup[hgrID]
+                val hgrIdx = data.habitGroups.indexOf(hgr)
+                data.subHabits[hgrIdx].remove(h)
+                data.removeWithID(id)
+                data.removeWithPos(position)
+                data.decrementPositions(position + 1, data.positionTypes.size)
+                listener.onItemRemoved(position)
+            }
+        } else if (type == HABIT_GROUP) {
+            val hgr = data.idToHabitGroup[id]
+            if (hgr != null) {
+                val hgrIdx = data.positionIndices[position]
+
+                for (habit in data.subHabits[hgrIdx].reversed()) {
+                    val habitPos = data.idToPosition[habit.id]!!
+                    data.removeWithID(habit.id)
+                    listener.onItemRemoved(habitPos)
+                }
+                data.subHabits.removeAt(hgrIdx)
+                data.habitGroups.removeAt(hgrIdx)
+                data.removeWithID(hgr.id)
+                data.rebuildPositions()
+                listener.onItemRemoved(position)
+            }
+        }
     }
 
     @Synchronized
     fun reorder(from: Int, to: Int) {
-        val fromHabit = data.habits[from]
+        if (from == to) return
-        data.habits.removeAt(from)
+        val type = data.positionTypes[from]
-        data.habits.add(to, fromHabit)
+        if (type == STANDALONE_HABIT || type == SUB_HABIT) {
-        listener.onItemMoved(from, to)
+            val habit = data.positionToHabit[from]!!
+            data.performMove(habit, from, to)
+        } else {
+            val habitGroup = data.positionToHabitGroup[from]!!
+            data.performMove(habitGroup, from, to)
+        }
     }
 
     @Synchronized
@@ -188,7 +273,8 @@ class HabitCardListCache @Inject constructor(
 
     @Synchronized
     fun setFilter(matcher: HabitMatcher) {
-        filteredHabits = allHabits.getFiltered(matcher)
+        filteredHabits = habits.getFiltered(matcher)
+        filteredHabitGroups = habitGroups.getFiltered(matcher)
     }
 
     @Synchronized
@@ -210,7 +296,15 @@ class HabitCardListCache @Inject constructor(
 
     private inner class CacheData {
         val idToHabit: HashMap<Long?, Habit> = HashMap()
+        val idToHabitGroup: HashMap<Long?, HabitGroup> = HashMap()
         val habits: MutableList<Habit>
+        val habitGroups: MutableList<HabitGroup>
+        val subHabits: MutableList<MutableList<Habit>>
+        val idToPosition: HashMap<Long?, Int>
+        val positionTypes: MutableList<Int>
+        val positionIndices: MutableList<Int>
+        val positionToHabit: HashMap<Int, Habit>
+        val positionToHabitGroup: HashMap<Int, HabitGroup>
         val checkmarks: HashMap<Long?, IntArray>
         val scores: HashMap<Long?, Double>
         val notes: HashMap<Long?, Array<String>>
@@ -243,12 +337,20 @@ class HabitCardListCache @Inject constructor(
 
         @Synchronized
         fun copyScoresFrom(oldData: CacheData) {
-            for (id in idToHabit.keys) {
+            for (uuid in idToHabit.keys) {
-                if (oldData.scores.containsKey(id)) {
+                if (oldData.scores.containsKey(uuid)) {
-                    scores[id] =
+                    scores[uuid] =
-                        oldData.scores[id]!!
+                        oldData.scores[uuid]!!
+                } else {
+                    scores[uuid] = 0.0
+                }
+            }
+            for (uuid in idToHabitGroup.keys) {
+                if (oldData.scores.containsKey(uuid)) {
+                    scores[uuid] =
+                        oldData.scores[uuid]!!
                 } else {
-                    scores[id] = 0.0
+                    scores[uuid] = 0.0
                 }
             }
         }
@@ -256,17 +358,221 @@ class HabitCardListCache @Inject constructor(
         @Synchronized
         fun fetchHabits() {
             for (h in filteredHabits) {
-                if (h.id == null) continue
+                if (h.uuid == null) continue
                 habits.add(h)
+            }
+
+            for (hgr in filteredHabitGroups) {
+                if (hgr.uuid == null) continue
+                habitGroups.add(hgr)
+                val habitList = LinkedList<Habit>()
+                for (h in hgr.habitList) {
+                    habitList.add(h)
+                }
+                subHabits.add(habitList)
+            }
+        }
+
+        @Synchronized
+        fun rebuildPositions() {
+            positionToHabit.clear()
+            positionToHabitGroup.clear()
+            idToPosition.clear()
+            positionTypes.clear()
+            positionIndices.clear()
+            var position = 0
+            for ((idx, h) in habits.withIndex()) {
                 idToHabit[h.id] = h
+                idToPosition[h.id] = position
+                positionToHabit[position] = h
+                positionTypes.add(STANDALONE_HABIT)
+                positionIndices.add(idx)
+                position++
+            }
+
+            for ((idx, hgr) in habitGroups.withIndex()) {
+                idToHabitGroup[hgr.id] = hgr
+                idToPosition[hgr.id] = position
+                positionToHabitGroup[position] = hgr
+                positionTypes.add(HABIT_GROUP)
+                positionIndices.add(idx)
+                val habitList = subHabits[idx]
+                position++
+
+                for ((hIdx, h) in habitList.withIndex()) {
+                    idToHabit[h.id] = h
+                    idToPosition[h.id] = position
+                    positionToHabit[position] = h
+                    positionTypes.add(SUB_HABIT)
+                    positionIndices.add(hIdx)
+                    position++
+                }
+            }
+        }
+
+        @Synchronized
+        fun isValidInsert(habit: Habit, position: Int): Boolean {
+            if (habit.groupId == null) {
+                return position <= habits.size
+            } else {
+                val parent = idToHabitGroup[habit.groupId] ?: return false
+                val parentPosition = idToPosition[habit.groupId]!!
+                val parentIndex = habitGroups.indexOf(parent)
+                val nextGroup = habitGroups.getOrNull(parentIndex + 1)
+                val nextGroupPosition = idToPosition[nextGroup?.id]
+                return (position > parentPosition && position <= positionTypes.size) && (nextGroupPosition == null || position <= nextGroupPosition)
             }
         }
 
+        @Synchronized
+        fun isValidInsert(habitGroup: HabitGroup, position: Int): Boolean {
+            return (position == positionTypes.size) || (positionTypes[position] == HABIT_GROUP)
+        }
+
+        @Synchronized
+        fun incrementPositions(from: Int, to: Int) {
+            for (pos in positionToHabit.keys.sortedDescending()) {
+                if (pos in from..to) {
+                    positionToHabit[pos + 1] = positionToHabit[pos]!!
+                    positionToHabit.remove(pos)
+                }
+            }
+            for (pos in positionToHabitGroup.keys.sortedDescending()) {
+                if (pos in from..to) {
+                    positionToHabitGroup[pos + 1] = positionToHabitGroup[pos]!!
+                    positionToHabitGroup.remove(pos)
+                }
+            }
+            for ((key, pos) in idToPosition.entries) {
+                if (pos in from..to) {
+                    idToPosition[key] = pos + 1
+                }
+            }
+        }
+
+        @Synchronized
+        fun decrementPositions(fromPosition: Int, toPosition: Int) {
+            for (pos in positionToHabit.keys.sorted()) {
+                if (pos in fromPosition..toPosition) {
+                    positionToHabit[pos - 1] = positionToHabit[pos]!!
+                    positionToHabit.remove(pos)
+                }
+            }
+            for (pos in positionToHabitGroup.keys.sorted()) {
+                if (pos in fromPosition..toPosition) {
+                    positionToHabitGroup[pos - 1] = positionToHabitGroup[pos]!!
+                    positionToHabitGroup.remove(pos)
+                }
+            }
+            for ((key, pos) in idToPosition.entries) {
+                if (pos in fromPosition..toPosition) {
+                    idToPosition[key] = pos - 1
+                }
+            }
+        }
+
+        @Synchronized
+        fun performMove(
+            habit: Habit,
+            fromPosition: Int,
+            toPosition: Int
+        ) {
+            val type = positionTypes[fromPosition]
+            if (type == HABIT_GROUP) return
+
+            // Workaround for https://github.com/iSoron/uhabits/issues/968
+            val checkedToPosition = if (toPosition >= positionTypes.size) {
+                logger.error("performMove: $toPosition for habit is strictly higher than ${habits.size}")
+                positionTypes.size - 1
+            } else {
+                toPosition
+            }
+
+            val verifyPosition = if (fromPosition > checkedToPosition) checkedToPosition else checkedToPosition + 1
+            if (!isValidInsert(habit, verifyPosition)) return
+
+            if (type == STANDALONE_HABIT) {
+                habits.removeAt(fromPosition)
+                removeWithPos(fromPosition)
+                if (fromPosition < checkedToPosition) {
+                    decrementPositions(fromPosition + 1, checkedToPosition)
+                } else {
+                    incrementPositions(checkedToPosition, fromPosition - 1)
+                }
+                habits.add(checkedToPosition, habit)
+                positionTypes.add(checkedToPosition, STANDALONE_HABIT)
+                positionIndices.add(checkedToPosition, checkedToPosition)
+            } else {
+                val hgr = idToHabitGroup[habit.groupId]
+                val hgrIdx = habitGroups.indexOf(hgr)
+                val fromIdx = positionIndices[fromPosition]
+                subHabits[hgrIdx].removeAt(fromIdx)
+                removeWithPos(fromPosition)
+                if (fromPosition < checkedToPosition) {
+                    decrementPositions(fromPosition + 1, checkedToPosition)
+                } else {
+                    incrementPositions(checkedToPosition, fromPosition - 1)
+                }
+                val toIdx = checkedToPosition - idToPosition[hgr!!.id]!! - 1
+                subHabits[hgrIdx].add(toIdx, habit)
+                positionTypes.add(checkedToPosition, SUB_HABIT)
+                positionIndices.add(checkedToPosition, toIdx)
+            }
+
+            positionToHabit[checkedToPosition] = habit
+            idToPosition[habit.id] = checkedToPosition
+            listener.onItemMoved(fromPosition, checkedToPosition)
+        }
+
+        @Synchronized
+        fun performMove(
+            habitGroup: HabitGroup,
+            fromPosition: Int,
+            toPosition: Int
+        ) {
+            if (positionTypes[fromPosition] != HABIT_GROUP) return
+            if (!isValidInsert(habitGroup, toPosition)) return
+            val fromIdx = positionIndices[fromPosition]
+            val habitList = subHabits[fromIdx]
+            val toIdx = habitGroups.indexOf(positionToHabitGroup[toPosition])
+
+            habitGroups.removeAt(fromIdx)
+            subHabits.removeAt(fromIdx)
+
+            habitGroups.add(toIdx, habitGroup)
+            subHabits.add(toIdx, habitList)
+
+            rebuildPositions()
+            listener.onItemMoved(fromPosition, toPosition)
+        }
+
+        fun removeWithID(id: Long?) {
+            idToPosition.remove(id)
+            idToHabit.remove(id)
+            idToHabitGroup.remove(id)
+            scores.remove(id)
+            notes.remove(id)
+            checkmarks.remove(id)
+        }
+
+        fun removeWithPos(pos: Int) {
+            positionTypes.removeAt(pos)
+            positionIndices.removeAt(pos)
+            positionToHabit.remove(pos)
+        }
+
         /**
          * Creates a new CacheData without any content.
          */
         init {
             habits = LinkedList()
+            habitGroups = LinkedList()
+            subHabits = LinkedList()
+            positionTypes = LinkedList()
+            positionIndices = LinkedList()
+            idToPosition = HashMap()
+            positionToHabit = HashMap()
+            positionToHabitGroup = HashMap()
             checkmarks = HashMap()
             scores = HashMap()
             notes = HashMap()
@@ -275,19 +581,19 @@ class HabitCardListCache @Inject constructor(
 
     private inner class RefreshTask : Task {
         private val newData: CacheData
-        private val targetId: Long?
+        private val targetID: Long?
         private var isCancelled = false
         private var runner: TaskRunner? = null
 
         constructor() {
             newData = CacheData()
-            targetId = null
+            targetID = null
             isCancelled = false
         }
 
-        constructor(targetId: Long) {
+        constructor(targetID: Long) {
             newData = CacheData()
-            this.targetId = targetId
+            this.targetID = targetID
         }
 
         @Synchronized
@@ -298,27 +604,35 @@ class HabitCardListCache @Inject constructor(
         @Synchronized
         override fun doInBackground() {
             newData.fetchHabits()
+            newData.rebuildPositions()
             newData.copyScoresFrom(data)
             newData.copyCheckmarksFrom(data)
             newData.copyNoteIndicatorsFrom(data)
             val today = getTodayWithOffset()
             val dateFrom = today.minus(checkmarkCount - 1)
             if (runner != null) runner!!.publishProgress(this, -1)
-            for (position in newData.habits.indices) {
+            for ((position, type) in newData.positionTypes.withIndex()) {
                 if (isCancelled) return
-                val habit = newData.habits[position]
+                if (type == STANDALONE_HABIT || type == SUB_HABIT) {
-                if (targetId != null && targetId != habit.id) continue
+                    val habit = newData.positionToHabit[position]!!
-                newData.scores[habit.id] = habit.scores[today].value
+                    if (targetID != null && targetID != habit.id) continue
-                val list: MutableList<Int> = ArrayList()
+                    newData.scores[habit.id] = habit.scores[today].value
-                val notes: MutableList<String> = ArrayList()
+                    val list: MutableList<Int> = ArrayList()
-                for ((_, value, note) in habit.computedEntries.getByInterval(dateFrom, today)) {
+                    val notes: MutableList<String> = ArrayList()
-                    list.add(value)
+                    for ((_, value, note) in habit.computedEntries.getByInterval(dateFrom, today)) {
-                    notes.add(note)
+                        list.add(value)
+                        notes.add(note)
+                    }
+                    val entries = list.toTypedArray()
+                    newData.checkmarks[habit.id] = ArrayUtils.toPrimitive(entries)
+                    newData.notes[habit.id] = notes.toTypedArray()
+                    runner!!.publishProgress(this, position)
+                } else if (type == HABIT_GROUP) {
+                    val habitGroup = newData.positionToHabitGroup[position]!!
+                    if (targetID != null && targetID != habitGroup.id) continue
+                    newData.scores[habitGroup.id] = habitGroup.scores[today].value
+                    runner!!.publishProgress(this, position)
                 }
-                val entries = list.toTypedArray()
-                newData.checkmarks[habit.id] = ArrayUtils.toPrimitive(entries)
-                newData.notes[habit.id] = notes.toTypedArray()
-                runner!!.publishProgress(this, position)
             }
         }
 
@@ -340,8 +654,23 @@ class HabitCardListCache @Inject constructor(
 
         @Synchronized
         private fun performInsert(habit: Habit, position: Int) {
+            if (!data.isValidInsert(habit, position)) return
             val id = habit.id
-            data.habits.add(position, habit)
+            if (habit.groupId == null) {
+                data.habits.add(position, habit)
+                data.positionTypes.add(position, STANDALONE_HABIT)
+                data.positionIndices.add(position, position)
+            } else {
+                val hgrPos = data.idToPosition[habit.groupId]!!
+                val hgrIdx = data.positionIndices[hgrPos]
+                val habitIndex = newData.positionIndices[position]
+                data.subHabits[hgrIdx].add(habitIndex, habit)
+                data.positionTypes.add(position, SUB_HABIT)
+                data.positionIndices.add(position, habitIndex)
+            }
+            data.incrementPositions(position, data.positionTypes.size - 1)
+            data.positionToHabit[position] = habit
+            data.idToPosition[id] = position
             data.idToHabit[id] = habit
             data.scores[id] = newData.scores[id]!!
             data.checkmarks[id] = newData.checkmarks[id]!!
@@ -350,76 +679,119 @@ class HabitCardListCache @Inject constructor(
         }
 
         @Synchronized
-        private fun performMove(
+        private fun performInsert(habitGroup: HabitGroup, position: Int) {
-            habit: Habit,
+            if (!data.isValidInsert(habitGroup, position)) return
-            fromPosition: Int,
+            val id = habitGroup.id
-            toPosition: Int
+            val prevIdx = newData.positionIndices[position]
-        ) {
+            val habitList = newData.subHabits[prevIdx]
-            data.habits.removeAt(fromPosition)
+            val idx = if (position < data.positionIndices.size) {
-
+                data.positionIndices[position]
-            // Workaround for https://github.com/iSoron/uhabits/issues/968
-            val checkedToPosition = if (toPosition > data.habits.size) {
-                logger.error("performMove: $toPosition is strictly higher than ${data.habits.size}")
-                data.habits.size
             } else {
-                toPosition
+                data.habitGroups.size
             }
 
-            data.habits.add(checkedToPosition, habit)
+            data.habitGroups.add(idx, habitGroup)
-            listener.onItemMoved(fromPosition, checkedToPosition)
+            data.subHabits.add(idx, habitList)
+            data.scores[id] = newData.scores[id]!!
+            for (h in habitList) {
+                data.scores[h.id] = newData.scores[h.id]!!
+                data.checkmarks[h.id] = newData.checkmarks[h.id]!!
+                data.notes[h.id] = newData.notes[h.id]!!
+            }
+            data.rebuildPositions()
+            listener.onItemInserted(position)
         }
 
         @Synchronized
         private fun performUpdate(id: Long, position: Int) {
+            var unchanged = true
             val oldScore = data.scores[id]!!
-            val oldCheckmarks = data.checkmarks[id]
-            val oldNoteIndicators = data.notes[id]
             val newScore = newData.scores[id]!!
-            val newCheckmarks = newData.checkmarks[id]!!
-            val newNoteIndicators = newData.notes[id]!!
-            var unchanged = true
             if (oldScore != newScore) unchanged = false
-            if (!Arrays.equals(oldCheckmarks, newCheckmarks)) unchanged = false
+
-            if (!Arrays.equals(oldNoteIndicators, newNoteIndicators)) unchanged = false
+            if (data.positionTypes[position] != HABIT_GROUP) {
+                val oldCheckmarks = data.checkmarks[id]
+                val newCheckmarks = newData.checkmarks[id]!!
+                val oldNoteIndicators = data.notes[id]
+                val newNoteIndicators = newData.notes[id]!!
+                if (!Arrays.equals(oldCheckmarks, newCheckmarks)) unchanged = false
+                if (!Arrays.equals(oldNoteIndicators, newNoteIndicators)) unchanged = false
+                if (unchanged) return
+                data.checkmarks[id] = newCheckmarks
+                data.notes[id] = newNoteIndicators
+            }
+
             if (unchanged) return
             data.scores[id] = newScore
-            data.checkmarks[id] = newCheckmarks
-            data.notes[id] = newNoteIndicators
             listener.onItemChanged(position)
         }
 
         @Synchronized
         private fun processPosition(currentPosition: Int) {
-            val habit = newData.habits[currentPosition]
+            val type = newData.positionTypes[currentPosition]
-            val id = habit.id
+
-            val prevPosition = data.habits.indexOf(habit)
+            if (type == STANDALONE_HABIT || type == SUB_HABIT) {
-            if (prevPosition < 0) {
+                val habit = newData.positionToHabit[currentPosition]!!
-                performInsert(habit, currentPosition)
+                val id = habit.id ?: throw NullPointerException()
-            } else {
+                val prevPosition = data.idToPosition[id] ?: -1
-                if (prevPosition != currentPosition) {
+                val newPosition = if (type == STANDALONE_HABIT) {
-                    performMove(
+                    currentPosition
-                        habit,
+                } else {
-                        prevPosition,
+                    val hgrPos = data.idToPosition[habit.groupId]!!
-                        currentPosition
+                    val hgrIdx = data.positionIndices[hgrPos]
-                    )
+                    newData.subHabits[hgrIdx].indexOf(habit) + hgrPos + 1
+                }
+                if (prevPosition < 0) {
+                    performInsert(habit, newPosition)
+                } else {
+                    if (prevPosition != newPosition) {
+                        data.performMove(
+                            habit,
+                            prevPosition,
+                            newPosition
+                        )
+                    }
+                    performUpdate(id, currentPosition)
+                }
+            } else if (type == HABIT_GROUP) {
+                val habitGroup = newData.positionToHabitGroup[currentPosition]!!
+                val id = habitGroup.id ?: throw NullPointerException()
+                val prevPosition = data.idToPosition[id] ?: -1
+                if (prevPosition < 0) {
+                    performInsert(habitGroup, currentPosition)
+                } else {
+                    if (prevPosition != currentPosition) {
+                        data.performMove(
+                            habitGroup,
+                            prevPosition,
+                            currentPosition
+                        )
+                    }
+                    performUpdate(id, currentPosition)
                 }
-                if (id == null) throw NullPointerException()
-                performUpdate(id, currentPosition)
             }
         }
 
         @Synchronized
         private fun processRemovedHabits() {
-            val before: Set<Long?> = data.idToHabit.keys
+            val before: Set<Long?> = (data.idToHabit.keys).union(data.idToHabitGroup.keys)
-            val after: Set<Long?> = newData.idToHabit.keys
+            val after: Set<Long?> = (newData.idToHabit.keys).union(newData.idToHabitGroup.keys)
             val removed: MutableSet<Long?> = TreeSet(before)
             removed.removeAll(after)
-            for (id in removed) remove(id!!)
+            for (id in removed.sortedBy { data.idToPosition[it] }) remove(id!!)
         }
     }
 
+    companion object {
+        const val STANDALONE_HABIT = 0
+        const val HABIT_GROUP = 1
+        const val SUB_HABIT = 2
+    }
+
     init {
-        filteredHabits = allHabits
+        filteredHabits = habits
+        filteredHabitGroups = habitGroups
+
         this.taskRunner = taskRunner
         listener = object : Listener {}
         data = CacheData()

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/list/ListHabitsBehavior.kt

@@ -20,8 +20,11 @@ package org.isoron.uhabits.core.ui.screens.habits.list
 
 import org.isoron.uhabits.core.commands.CommandRunner
 import org.isoron.uhabits.core.commands.CreateRepetitionCommand
+import org.isoron.uhabits.core.commands.RefreshParentGroupCommand
 import org.isoron.uhabits.core.models.Entry.Companion.YES_MANUAL
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.HabitType
 import org.isoron.uhabits.core.models.NumericalHabitType.AT_LEAST
@@ -40,6 +43,7 @@ import kotlin.math.roundToInt
 
 open class ListHabitsBehavior @Inject constructor(
     private val habitList: HabitList,
+    private val habitGroupList: HabitGroupList,
     private val dirFinder: DirFinder,
     private val taskRunner: TaskRunner,
     private val screen: Screen,
@@ -51,7 +55,12 @@ open class ListHabitsBehavior @Inject constructor(
         screen.showHabitScreen(h)
     }
 
+    fun onClickHabitGroup(hgr: HabitGroup) {
+        screen.showHabitGroupScreen(hgr)
+    }
+
     fun onEdit(habit: Habit, timestamp: Timestamp?) {
+        val list = if (habit.isSubHabit()) habit.group!!.habitList else habitList
         val entry = habit.computedEntries.get(timestamp!!)
         if (habit.type == HabitType.NUMERICAL) {
             val oldValue = entry.value.toDouble() / 1000
@@ -65,7 +74,8 @@ open class ListHabitsBehavior @Inject constructor(
                         screen.showConfetti(habit.color, x, y)
                     }
                 }
-                commandRunner.run(CreateRepetitionCommand(habitList, habit, timestamp, value, newNotes))
+                commandRunner.run(CreateRepetitionCommand(list, habit, timestamp, value, newNotes))
+                commandRunner.run(RefreshParentGroupCommand(habit, habitGroupList))
             }
         } else {
             screen.showCheckmarkPopup(
@@ -74,7 +84,8 @@ open class ListHabitsBehavior @Inject constructor(
                 habit.color
             ) { newValue: Int, newNotes: String, x: Float, y: Float ->
                 if (newValue != entry.value && newValue == YES_MANUAL) screen.showConfetti(habit.color, x, y)
-                commandRunner.run(CreateRepetitionCommand(habitList, habit, timestamp, newValue, newNotes))
+                commandRunner.run(CreateRepetitionCommand(list, habit, timestamp, newValue, newNotes))
+                commandRunner.run(RefreshParentGroupCommand(habit, habitGroupList))
             }
         }
     }
@@ -103,7 +114,14 @@ open class ListHabitsBehavior @Inject constructor(
     }
 
     fun onReorderHabit(from: Habit, to: Habit) {
-        taskRunner.execute { habitList.reorder(from, to) }
+        if (from.group == to.group) {
+            val list = from.group?.habitList ?: habitList
+            taskRunner.execute { list.reorder(from, to) }
+        }
+    }
+
+    fun onReorderHabitGroup(from: HabitGroup, to: HabitGroup) {
+        taskRunner.execute { habitGroupList.reorder(from, to) }
     }
 
     fun onRepairDB() {
@@ -130,8 +148,12 @@ open class ListHabitsBehavior @Inject constructor(
     }
 
     fun onToggle(habit: Habit, timestamp: Timestamp, value: Int, notes: String, x: Float, y: Float) {
+        val list = if (habit.isSubHabit()) habit.group!!.habitList else habitList
+        commandRunner.run(
+            CreateRepetitionCommand(list, habit, timestamp, value, notes)
+        )
         commandRunner.run(
-            CreateRepetitionCommand(habitList, habit, timestamp, value, notes)
+            RefreshParentGroupCommand(habit, habitGroupList)
         )
         if (value == YES_MANUAL) screen.showConfetti(habit.color, x, y)
     }
@@ -178,6 +200,7 @@ open class ListHabitsBehavior @Inject constructor(
 
     interface Screen {
         fun showHabitScreen(h: Habit)
+        fun showHabitGroupScreen(hgr: HabitGroup)
         fun showIntroScreen()
         fun showMessage(m: Message)
         fun showNumberPopup(

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/list/ListHabitsMenuBehavior.kt

@@ -33,8 +33,8 @@ class ListHabitsMenuBehavior @Inject constructor(
     private var showCompleted: Boolean
     private var showArchived: Boolean
 
-    fun onCreateHabit() {
+    fun onCreateHabit(groupId: Long? = null) {
-        screen.showSelectHabitTypeDialog()
+        screen.showSelectHabitTypeDialog(groupId)
     }
 
     fun onViewFAQ() {
@@ -132,7 +132,7 @@ class ListHabitsMenuBehavior @Inject constructor(
         fun showAboutScreen()
         fun showFAQScreen()
         fun showSettingsScreen()
-        fun showSelectHabitTypeDialog()
+        fun showSelectHabitTypeDialog(groupId: Long? = null)
     }
 
     init {

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/list/ListHabitsSelectionMenuBehavior.kt

@@ -18,12 +18,20 @@
  */
 package org.isoron.uhabits.core.ui.screens.habits.list
 
+import org.isoron.uhabits.core.commands.ArchiveHabitGroupsCommand
 import org.isoron.uhabits.core.commands.ArchiveHabitsCommand
 import org.isoron.uhabits.core.commands.ChangeHabitColorCommand
+import org.isoron.uhabits.core.commands.ChangeHabitGroupColorCommand
 import org.isoron.uhabits.core.commands.CommandRunner
+import org.isoron.uhabits.core.commands.DeleteHabitGroupsCommand
 import org.isoron.uhabits.core.commands.DeleteHabitsCommand
+import org.isoron.uhabits.core.commands.RefreshParentGroupCommand
+import org.isoron.uhabits.core.commands.RemoveFromGroupCommand
+import org.isoron.uhabits.core.commands.UnarchiveHabitGroupsCommand
 import org.isoron.uhabits.core.commands.UnarchiveHabitsCommand
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
 import org.isoron.uhabits.core.models.HabitList
 import org.isoron.uhabits.core.models.PaletteColor
 import org.isoron.uhabits.core.ui.callbacks.OnColorPickedCallback
@@ -32,33 +40,67 @@ import javax.inject.Inject
 
 class ListHabitsSelectionMenuBehavior @Inject constructor(
     private val habitList: HabitList,
+    private val habitGroupList: HabitGroupList,
     private val screen: Screen,
     private val adapter: Adapter,
     var commandRunner: CommandRunner
 ) {
     fun canArchive(): Boolean {
-        for (habit in adapter.getSelected()) if (habit.isArchived) return false
+        for (habit in adapter.getSelectedHabits()) if (habit.isArchived) return false
+        for (hgr in adapter.getSelectedHabitGroups()) if (hgr.isArchived) return false
         return true
     }
 
     fun canEdit(): Boolean {
-        return adapter.getSelected().size == 1
+        return (adapter.getSelectedHabits().size + adapter.getSelectedHabitGroups().size == 1)
     }
 
     fun canUnarchive(): Boolean {
-        for (habit in adapter.getSelected()) if (!habit.isArchived) return false
+        for (habit in adapter.getSelectedHabits()) if (!habit.isArchived) return false
+        for (hgr in adapter.getSelectedHabitGroups()) if (!hgr.isArchived) return false
         return true
     }
 
+    fun areSubHabits(): Boolean {
+        if (adapter.getSelectedHabitGroups().isNotEmpty()) return false
+        return (adapter.getSelectedHabits().all { it.isSubHabit() })
+    }
+
+    fun areHabits(): Boolean {
+        return adapter.getSelectedHabitGroups().isEmpty()
+    }
+
     fun onArchiveHabits() {
-        commandRunner.run(ArchiveHabitsCommand(habitList, adapter.getSelected()))
+        commandRunner.run(ArchiveHabitsCommand(habitList, adapter.getSelectedHabits()))
+        commandRunner.run(ArchiveHabitGroupsCommand(habitGroupList, adapter.getSelectedHabitGroups()))
+        for (habit in adapter.getSelectedHabits()) {
+            commandRunner.run(RefreshParentGroupCommand(habit, habitGroupList))
+        }
         adapter.clearSelection()
     }
 
     fun onChangeColor() {
-        val (color) = adapter.getSelected()[0]
+        val color = if (adapter.getSelectedHabits().isNotEmpty()) {
+            adapter.getSelectedHabits()[0].color
+        } else {
+            adapter.getSelectedHabitGroups()[0].color
+        }
+
         screen.showColorPicker(color) { selectedColor: PaletteColor ->
-            commandRunner.run(ChangeHabitColorCommand(habitList, adapter.getSelected(), selectedColor))
+            commandRunner.run(
+                ChangeHabitColorCommand(
+                    habitList,
+                    adapter.getSelectedHabits(),
+                    selectedColor
+                )
+            )
+            commandRunner.run(
+                ChangeHabitGroupColorCommand(
+                    habitGroupList,
+                    adapter.getSelectedHabitGroups(),
+                    selectedColor
+                )
+            )
             adapter.clearSelection()
         }
     }
@@ -66,29 +108,58 @@ class ListHabitsSelectionMenuBehavior @Inject constructor(
     fun onDeleteHabits() {
         screen.showDeleteConfirmationScreen(
             {
-                adapter.performRemove(adapter.getSelected())
+                adapter.performRemove(adapter.getSelectedHabits())
-                commandRunner.run(DeleteHabitsCommand(habitList, adapter.getSelected()))
+                adapter.performRemoveHabitGroup(adapter.getSelectedHabitGroups())
+                commandRunner.run(DeleteHabitGroupsCommand(habitGroupList, adapter.getSelectedHabitGroups()))
+                commandRunner.run(DeleteHabitsCommand(habitList, adapter.getSelectedHabits()))
+                for (habit in adapter.getSelectedHabits()) {
+                    commandRunner.run(RefreshParentGroupCommand(habit, habitGroupList))
+                }
                 adapter.clearSelection()
             },
-            adapter.getSelected().size
+            adapter.getSelectedHabits().size + adapter.getSelectedHabitGroups().size
         )
     }
 
     fun onEditHabits() {
-        val selected = adapter.getSelected()
+        val selected = adapter.getSelectedHabits()
-        if (selected.isNotEmpty()) screen.showEditHabitsScreen(selected)
+        if (selected.isNotEmpty()) {
+            screen.showEditHabitsScreen(selected)
+        } else {
+            val selectedGroup = adapter.getSelectedHabitGroups()
+            screen.showEditHabitGroupScreen(selectedGroup)
+        }
+
         adapter.clearSelection()
     }
 
     fun onUnarchiveHabits() {
-        commandRunner.run(UnarchiveHabitsCommand(habitList, adapter.getSelected()))
+        commandRunner.run(UnarchiveHabitsCommand(habitList, adapter.getSelectedHabits()))
+        commandRunner.run(UnarchiveHabitGroupsCommand(habitGroupList, adapter.getSelectedHabitGroups()))
+        for (habit in adapter.getSelectedHabits()) {
+            commandRunner.run(RefreshParentGroupCommand(habit, habitGroupList))
+        }
+        adapter.clearSelection()
+    }
+
+    fun onRemoveFromGroup() {
+        adapter.performRemove(adapter.getSelectedHabits())
+        commandRunner.run(RemoveFromGroupCommand(habitList, adapter.getSelectedHabits()))
+        adapter.clearSelection()
+    }
+
+    fun onAddToGroup() {
+        adapter.performRemove(adapter.getSelectedHabits())
+        screen.showHabitGroupPickerDialog(adapter.getSelectedHabits())
         adapter.clearSelection()
     }
 
     interface Adapter {
         fun clearSelection()
-        fun getSelected(): List<Habit>
+        fun getSelectedHabits(): List<Habit>
+        fun getSelectedHabitGroups(): List<HabitGroup>
         fun performRemove(selected: List<Habit>)
+        fun performRemoveHabitGroup(selected: List<HabitGroup>)
     }
 
     interface Screen {
@@ -103,5 +174,8 @@ class ListHabitsSelectionMenuBehavior @Inject constructor(
         )
 
         fun showEditHabitsScreen(selected: List<Habit>)
+
+        fun showEditHabitGroupScreen(selected: List<HabitGroup>)
+        fun showHabitGroupPickerDialog(selected: List<Habit>)
     }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/show/ShowHabitGroup.kt

@@ -0,0 +1,117 @@
+package org.isoron.uhabits.core.ui.screens.habits.show
+
+import org.isoron.uhabits.core.commands.CommandRunner
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.PaletteColor
+import org.isoron.uhabits.core.preferences.Preferences
+import org.isoron.uhabits.core.ui.screens.habits.show.views.BarCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.BarCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.FrequencyCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.FrequencyCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.NotesCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.NotesCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.OverviewCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.OverviewCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.ScoreCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.ScoreCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.StreakCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.StreakCartPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.SubtitleCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.SubtitleCardState
+import org.isoron.uhabits.core.ui.screens.habits.show.views.TargetCardPresenter
+import org.isoron.uhabits.core.ui.screens.habits.show.views.TargetCardState
+import org.isoron.uhabits.core.ui.views.Theme
+
+data class ShowHabitGroupState(
+    val title: String = "",
+    val isEmpty: Boolean = false,
+    val isNumerical: Boolean = false,
+    val isBoolean: Boolean = false,
+    val color: PaletteColor = PaletteColor(1),
+    val subtitle: SubtitleCardState,
+    val overview: OverviewCardState,
+    val notes: NotesCardState,
+    val target: TargetCardState,
+    val streaks: StreakCardState,
+    val scores: ScoreCardState,
+    val frequency: FrequencyCardState,
+    val bar: BarCardState,
+    val theme: Theme
+)
+
+class ShowHabitGroupPresenter(
+    val habitGroup: HabitGroup,
+    val preferences: Preferences,
+    val screen: Screen,
+    val commandRunner: CommandRunner
+) {
+
+    val barCardPresenter = BarCardPresenter(
+        preferences = preferences,
+        screen = screen
+    )
+
+    val scoreCardPresenter = ScoreCardPresenter(
+        preferences = preferences,
+        screen = screen
+    )
+
+    companion object {
+        fun buildState(
+            habitGroup: HabitGroup,
+            preferences: Preferences,
+            theme: Theme
+        ): ShowHabitGroupState {
+            return ShowHabitGroupState(
+                title = habitGroup.name,
+                isEmpty = habitGroup.habitList.isEmpty,
+                isNumerical = habitGroup.habitList.all { it.isNumerical },
+                isBoolean = habitGroup.habitList.all { !it.isNumerical },
+                color = habitGroup.color,
+                theme = theme,
+                subtitle = SubtitleCardPresenter.buildState(
+                    habitGroup = habitGroup,
+                    theme = theme
+                ),
+                overview = OverviewCardPresenter.buildState(
+                    habitGroup = habitGroup,
+                    theme = theme
+                ),
+                notes = NotesCardPresenter.buildState(
+                    habitGroup = habitGroup
+                ),
+                target = TargetCardPresenter.buildState(
+                    habitGroup = habitGroup,
+                    firstWeekday = preferences.firstWeekdayInt,
+                    theme = theme
+                ),
+                streaks = StreakCartPresenter.buildState(
+                    habitGroup = habitGroup,
+                    theme = theme
+                ),
+                scores = ScoreCardPresenter.buildState(
+                    spinnerPosition = preferences.scoreCardSpinnerPosition,
+                    habitGroup = habitGroup,
+                    firstWeekday = preferences.firstWeekdayInt,
+                    theme = theme
+                ),
+                frequency = FrequencyCardPresenter.buildState(
+                    habitGroup = habitGroup,
+                    firstWeekday = preferences.firstWeekdayInt,
+                    theme = theme
+                ),
+                bar = BarCardPresenter.buildState(
+                    habitGroup = habitGroup,
+                    firstWeekday = preferences.firstWeekdayInt,
+                    boolSpinnerPosition = preferences.barCardBoolSpinnerPosition,
+                    numericalSpinnerPosition = preferences.barCardNumericalSpinnerPosition,
+                    theme = theme
+                )
+            )
+        }
+    }
+
+    interface Screen :
+        BarCardPresenter.Screen,
+        ScoreCardPresenter.Screen
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/show/ShowHabitGroupMenuPresenter.kt

@@ -0,0 +1,43 @@
+package org.isoron.uhabits.core.ui.screens.habits.show
+
+import org.isoron.uhabits.core.commands.CommandRunner
+import org.isoron.uhabits.core.commands.DeleteHabitGroupsCommand
+import org.isoron.uhabits.core.models.HabitGroup
+import org.isoron.uhabits.core.models.HabitGroupList
+import org.isoron.uhabits.core.ui.callbacks.OnConfirmedCallback
+import java.io.File
+
+class ShowHabitGroupMenuPresenter(
+    private val commandRunner: CommandRunner,
+    private val habitGroup: HabitGroup,
+    private val habitGroupList: HabitGroupList,
+    private val screen: Screen
+) {
+    fun onEditHabitGroup() {
+        screen.showEditHabitGroupScreen(habitGroup)
+    }
+
+    fun onDeleteHabitGroup() {
+        screen.showDeleteConfirmationScreen {
+            commandRunner.run(DeleteHabitGroupsCommand(habitGroupList, listOf(habitGroup)))
+            screen.close()
+        }
+    }
+
+    enum class Message {
+        COULD_NOT_EXPORT
+    }
+
+    interface Screen {
+        fun showEditHabitGroupScreen(habitGroup: HabitGroup)
+        fun showMessage(m: Message?)
+        fun showSendFileScreen(filename: String)
+        fun showDeleteConfirmationScreen(callback: OnConfirmedCallback)
+        fun close()
+        fun refresh()
+    }
+
+    interface System {
+        fun getCSVOutputDir(): File
+    }
+}

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/show/views/BarCard.kt

@@ -21,6 +21,7 @@ package org.isoron.uhabits.core.ui.screens.habits.show.views
 
 import org.isoron.uhabits.core.models.Entry
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.PaletteColor
 import org.isoron.uhabits.core.models.groupedSum
 import org.isoron.uhabits.core.preferences.Preferences
@@ -74,6 +75,53 @@ class BarCardPresenter(
                 boolSpinnerPosition = boolSpinnerPosition
             )
         }
+
+        fun buildState(
+            habitGroup: HabitGroup,
+            firstWeekday: Int,
+            numericalSpinnerPosition: Int,
+            boolSpinnerPosition: Int,
+            theme: Theme
+        ): BarCardState {
+            val isNumerical = habitGroup.habitList.all { it.isNumerical }
+            val isBoolean = habitGroup.habitList.all { !it.isNumerical }
+            if ((!isNumerical && !isBoolean) || habitGroup.habitList.isEmpty) {
+                return BarCardState(
+                    theme = theme,
+                    entries = listOf(Entry(DateUtils.getTodayWithOffset(), 0)),
+                    bucketSize = 1,
+                    color = habitGroup.color,
+                    isNumerical = isNumerical,
+                    numericalSpinnerPosition = numericalSpinnerPosition,
+                    boolSpinnerPosition = boolSpinnerPosition
+                )
+            }
+            val bucketSize = if (isNumerical) {
+                numericalBucketSizes[numericalSpinnerPosition]
+            } else {
+                boolBucketSizes[boolSpinnerPosition]
+            }
+            val today = DateUtils.getTodayWithOffset()
+            val allEntries = habitGroup.habitList.map { habit ->
+                val oldest = habit.computedEntries.getKnown().lastOrNull()?.timestamp ?: today
+                habit.computedEntries.getByInterval(oldest, today).groupedSum(
+                    truncateField = ScoreCardPresenter.getTruncateField(bucketSize),
+                    firstWeekday = firstWeekday,
+                    isNumerical = habit.isNumerical
+                )
+            }.flatten()
+
+            val summedEntries = allEntries.groupedSum()
+            return BarCardState(
+                theme = theme,
+                entries = summedEntries,
+                bucketSize = bucketSize,
+                color = habitGroup.color,
+                isNumerical = isNumerical,
+                numericalSpinnerPosition = numericalSpinnerPosition,
+                boolSpinnerPosition = boolSpinnerPosition
+            )
+        }
     }
 
     fun onNumericalSpinnerPosition(position: Int) {

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/show/views/FrequencyCard.kt

@@ -20,10 +20,10 @@
 package org.isoron.uhabits.core.ui.screens.habits.show.views
 
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.PaletteColor
 import org.isoron.uhabits.core.models.Timestamp
 import org.isoron.uhabits.core.ui.views.Theme
-import java.util.HashMap
 
 data class FrequencyCardState(
     val color: PaletteColor,
@@ -42,11 +42,57 @@ class FrequencyCardPresenter {
         ) = FrequencyCardState(
             color = habit.color,
             isNumerical = habit.isNumerical,
-            frequency = habit.originalEntries.computeWeekdayFrequency(
+            frequency = habit.computedEntries.computeWeekdayFrequency(
                 isNumerical = habit.isNumerical
             ),
             firstWeekday = firstWeekday,
             theme = theme
         )
+
+        fun buildState(
+            habitGroup: HabitGroup,
+            firstWeekday: Int,
+            theme: Theme
+        ): FrequencyCardState {
+            val frequencies = if (habitGroup.habitList.isEmpty) {
+                hashMapOf<Timestamp, Array<Int>>()
+            } else {
+                getFrequenciesFromHabitGroup(habitGroup)
+            }
+
+            return FrequencyCardState(
+                color = habitGroup.color,
+                isNumerical = true,
+                frequency = frequencies,
+                firstWeekday = firstWeekday,
+                theme = theme
+            )
+        }
+
+        fun getFrequenciesFromHabitGroup(habitGroup: HabitGroup): HashMap<Timestamp, Array<Int>> {
+            val normalizedEntries = habitGroup.habitList.map {
+                it.computedEntries.normalizeEntries(it.isNumerical, it.frequency, it.targetValue)
+            }
+            val frequencies = normalizedEntries.map {
+                it.computeWeekdayFrequency(isNumerical = true)
+            }.reduce { acc, hashMap ->
+                mergeMaps(acc, hashMap) { value1, value2 -> addArray(value1, value2) }
+            }
+            return frequencies
+        }
+
+        private fun <K, V> mergeMaps(map1: HashMap<K, V>, map2: HashMap<K, V>, mergeFunction: (V, V) -> V): HashMap<K, V> {
+            val result = map1 // Step 1
+            for ((key, value) in map2) { // Step 2
+                result[key] = result[key]?.let { existingValue ->
+                    mergeFunction(existingValue, value) // Step 3 (merge logic)
+                } ?: value
+            }
+            return result // Step 4
+        }
+
+        private fun addArray(array1: Array<Int>, array2: Array<Int>): Array<Int> {
+            return array1.zip(array2) { a, b -> a + b }.toTypedArray()
+        }
     }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/show/views/NotesCard.kt

@@ -20,6 +20,7 @@
 package org.isoron.uhabits.core.ui.screens.habits.show.views
 
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 
 data class NotesCardState(
     val description: String
@@ -30,5 +31,9 @@ class NotesCardPresenter {
         fun buildState(habit: Habit) = NotesCardState(
             description = habit.description
         )
+
+        fun buildState(habitGroup: HabitGroup) = NotesCardState(
+            description = habitGroup.description
+        )
     }
 }

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/ui/screens/habits/show/views/OverviewCard.kt

@@ -21,6 +21,7 @@ package org.isoron.uhabits.core.ui.screens.habits.show.views
 
 import org.isoron.uhabits.core.models.Entry
 import org.isoron.uhabits.core.models.Habit
+import org.isoron.uhabits.core.models.HabitGroup
 import org.isoron.uhabits.core.models.PaletteColor
 import org.isoron.uhabits.core.ui.views.Theme
 import org.isoron.uhabits.core.utils.DateUtils
@@ -57,5 +58,27 @@ class OverviewCardPresenter {
                 theme = theme
             )
         }
+
+        fun buildState(habitGroup: HabitGroup, theme: Theme): OverviewCardState {
+            val today = DateUtils.getTodayWithOffset()
+            val lastMonth = today.minus(30)
+            val lastYear = today.minus(365)
+            val scores = habitGroup.scores
+            val scoreToday = scores[today].value.toFloat()
+            val scoreLastMonth = scores[lastMonth].value.toFloat()
+            val scoreLastYear = scores[lastYear].value.toFloat()
+            val totalCount = habitGroup.habitList.sumOf { habit ->
+                habit.originalEntries.getKnown().count { it.value == Entry.YES_MANUAL }
+                    .toLong()
+            }
+            return OverviewCardState(
+                color = habitGroup.color,
+                scoreToday = scoreToday,
+                scoreMonthDiff = scoreToday - scoreLastMonth,
+                scoreYearDiff = scoreToday - scoreLastYear,
+                totalCount = totalCount,
+                theme = theme
+            )
+        }
     }
 }