Implement auto backups

app/src/main/java/org/isoron/helpers/ReplayableActivity.java

@@ -1,6 +1,7 @@
 package org.isoron.helpers;
 
 import android.app.Activity;
+import android.app.backup.BackupManager;
 import android.os.Bundle;
 import android.widget.Toast;
 
@@ -28,6 +29,7 @@ abstract public class ReplayableActivity extends Activity
     public void executeCommand(Command command)
     {
         executeCommand(command, false);
+        BackupManager.dataChanged("org.isoron.uhabits");
     }
 
     protected void undo()

app/src/main/java/org/isoron/uhabits/HabitsBackupAgent.java

@@ -0,0 +1,15 @@
+package org.isoron.uhabits;
+
+import android.app.backup.BackupAgentHelper;
+import android.app.backup.FileBackupHelper;
+import android.app.backup.SharedPreferencesBackupHelper;
+
+public class HabitsBackupAgent extends BackupAgentHelper
+{
+    @Override
+    public void onCreate()
+    {
+        addHelper("preferences", new SharedPreferencesBackupHelper(this, "preferences"));
+        addHelper("database", new FileBackupHelper(this, "../databases/uhabits.db"));
+    }
+}

app/src/main/java/org/isoron/uhabits/dialogs/SettingsFragment.java

@@ -1,12 +1,14 @@
 package org.isoron.uhabits.dialogs;
 
 
+import android.app.backup.BackupManager;
+import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.preference.PreferenceFragment;
 
 import org.isoron.uhabits.R;
 
-public class SettingsFragment extends PreferenceFragment
+public class SettingsFragment extends PreferenceFragment implements SharedPreferences.OnSharedPreferenceChangeListener
 {
     @Override
     public void onCreate(Bundle savedInstanceState)
@@ -14,4 +16,26 @@ public class SettingsFragment extends PreferenceFragment
         super.onCreate(savedInstanceState);
         addPreferencesFromResource(R.xml.preferences);
     }
+
+    @Override
+    public void onResume()
+    {
+        super.onResume();
+        getPreferenceManager().getSharedPreferences().
+                registerOnSharedPreferenceChangeListener(this);
+    }
+
+    @Override
+    public void onPause()
+    {
+        getPreferenceManager().getSharedPreferences().
+                unregisterOnSharedPreferenceChangeListener(this);
+        super.onPause();
+    }
+
+    @Override
+    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key)
+    {
+        BackupManager.dataChanged("org.isoron.uhabits");
+    }
 }