Rename night mode to dark theme; abide by system-wide settings (API 29)

Closes issue #513

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

@@ -19,6 +19,8 @@
 
 package org.isoron.uhabits.activities
 
+import android.content.res.Configuration.*
+import android.os.Build.VERSION.*
 import android.support.v4.content.*
 import org.isoron.androidbase.activities.*
 import org.isoron.uhabits.*
@@ -33,6 +35,16 @@ class AndroidThemeSwitcher
         preferences: Preferences
 ) : ThemeSwitcher(preferences) {
 
+    override fun getSystemTheme(): Int {
+        if(SDK_INT < 29) return THEME_LIGHT;
+        val uiMode = activity.resources.configuration.uiMode
+        return if ((uiMode and UI_MODE_NIGHT_MASK) == UI_MODE_NIGHT_YES) {
+            THEME_DARK;
+        } else {
+            THEME_LIGHT;
+        }
+    }
+
     override fun applyDarkTheme() {
         activity.setTheme(R.style.AppBaseThemeDark)
         activity.window.navigationBarColor =

android/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.java

@@ -27,14 +27,14 @@ import android.provider.*;
 import android.support.annotation.*;
 import android.support.v7.preference.*;
 
-import org.isoron.uhabits.*;
 import org.isoron.uhabits.R;
+import org.isoron.uhabits.*;
 import org.isoron.uhabits.core.preferences.*;
 import org.isoron.uhabits.core.ui.*;
 import org.isoron.uhabits.notifications.*;
 
 import static android.media.RingtoneManager.*;
-import static android.os.Build.VERSION.SDK_INT;
+import static android.os.Build.VERSION.*;
 import static org.isoron.uhabits.activities.habits.list.ListHabitsScreenKt.*;
 
 public class SettingsFragment extends PreferenceFragmentCompat

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

@@ -169,9 +169,9 @@
     <string name="troubleshooting">Troubleshooting</string>
 
     <string name="help_translate">Help translate this app</string>
-    <string name="night_mode">Night mode</string>
-    <string name="use_pure_black">Use pure black in night mode</string>
-    <string name="pure_black_description">Replaces gray backgrounds with pure black in night mode. Reduces battery usage in phones with AMOLED display.</string>
+    <string name="night_mode">Dark theme</string>
+    <string name="use_pure_black">Use pure black in dark theme</string>
+    <string name="pure_black_description">Replaces gray backgrounds with pure black in dark theme. Reduces battery usage in phones with AMOLED display.</string>
     <string name="interface_preferences">Interface</string>
     <string name="reverse_days">Reverse order of days</string>
     <string name="reverse_days_description">Show days in reverse order on the main screen.</string>

android/uhabits-core/src/main/java/org/isoron/uhabits/core/preferences/Preferences.java

@@ -186,7 +186,7 @@ public class Preferences
 
     public int getTheme()
     {
-        return storage.getInt("pref_theme", ThemeSwitcher.THEME_LIGHT);
+        return storage.getInt("pref_theme", ThemeSwitcher.THEME_AUTOMATIC);
     }
 
     public void setTheme(int theme)

android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/ThemeSwitcher.java

@@ -27,7 +27,9 @@ public abstract class ThemeSwitcher
 {
     public static final int THEME_DARK = 1;
 
-    public static final int THEME_LIGHT = 0;
+    public static final int THEME_LIGHT = 2;
+
+    public static final int THEME_AUTOMATIC = 0;
 
     private final Preferences preferences;
 
@@ -38,7 +40,7 @@ public abstract class ThemeSwitcher
 
     public void apply()
     {
-        if (preferences.getTheme() == THEME_DARK)
+        if (isNightMode())
         {
             if (preferences.isPureBlackEnabled()) applyPureBlackTheme();
             else applyDarkTheme();
@@ -55,19 +57,36 @@ public abstract class ThemeSwitcher
 
     public abstract void applyPureBlackTheme();
 
+    public abstract int getSystemTheme();
+
     public boolean isNightMode()
     {
-        return preferences.getTheme() == THEME_DARK;
-    }
+        int systemTheme = getSystemTheme();
+        int userTheme = preferences.getTheme();
 
-    public void setTheme(int theme)
-    {
-        preferences.setTheme(theme);
+        return (userTheme == THEME_DARK ||
+                (systemTheme == THEME_DARK && userTheme == THEME_AUTOMATIC));
     }
 
     public void toggleNightMode()
     {
-        if (isNightMode()) setTheme(THEME_LIGHT);
-        else setTheme(THEME_DARK);
+        int systemTheme = getSystemTheme();
+        int userTheme = preferences.getTheme();
+
+        if(userTheme == THEME_AUTOMATIC)
+        {
+            if(systemTheme == THEME_LIGHT) preferences.setTheme(THEME_DARK);
+            if(systemTheme == THEME_DARK) preferences.setTheme(THEME_LIGHT);
+        }
+        else if(userTheme == THEME_LIGHT)
+        {
+            if (systemTheme == THEME_LIGHT) preferences.setTheme(THEME_DARK);
+            if (systemTheme == THEME_DARK) preferences.setTheme(THEME_AUTOMATIC);
+        }
+        else if(userTheme == THEME_DARK)
+        {
+            if (systemTheme == THEME_LIGHT) preferences.setTheme(THEME_AUTOMATIC);
+            if (systemTheme == THEME_DARK) preferences.setTheme(THEME_LIGHT);
+        }
     }
 }