How to move back from Preferences subscreen to main screen in PreferenceFragmentCompat?

Question

I am trying to implement a Settings screen using PreferenceFragmentCompat. My preference xml has a preference subscreen like this:

preferences.xml

    <CheckBoxPreference
        android:defaultValue="false"
        android:key="@string/pref_sound_key"
        android:summary="@string/pref_sound_summary"
        android:title="@string/pref_sound_title" />

    <PreferenceScreen android:title="Inner Screen">
        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_1"
            android:title="@string/title_1" />

        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_1"
            android:title="@string/title_1" />

        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_2"
            android:title="@string/title_2" />

        <CheckBoxPreference
            android:defaultValue="true"
            android:key="@string/key_3"
            android:title="@string/title_3" />
    </PreferenceScreen>

</PreferenceScreen>

Preference Main Screen

Now, in the app, the subscreen does not open until I implement PreferenceFragmentCompat.OnPreferenceStartScreenCallback interface in parent activity, as specified in PreferenceFragmentCompat doc.

MainActivity.java

public boolean onPreferenceStartScreen(PreferenceFragmentCompat preferenceFragmentCompat,
 PreferenceScreen preferenceScreen) {    
    preferenceFragmentCompat.setPreferenceScreen(preferenceScreen);
    return true;
}

Here's where the problem arises. On implementing the interface, the subscreen opens, but then there is no way I can find to move back to first screen.

Preference Subscreen

Pressing back key closes the app.

Is there any way I can put a back arrow on app bar so that pressing it will bring the main screen back?

Answer 1

By using setPreferenceScreen you are setting the root preference screen to the sub preference screen which is preventing you from having a hierarchy of preference screens to navigate back through.

I suggest that you treat each PreferenceScreen as a Fragment and add a new Fragment when you navigate into a sub screen.

@Override
public boolean onPreferenceStartScreen(PreferenceFragmentCompat preferenceFragmentCompat,
                                       PreferenceScreen preferenceScreen) {
    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    MyPreferenceFragment fragment = new MyPreferenceFragment();
    Bundle args = new Bundle();
    args.putString(PreferenceFragmentCompat.ARG_PREFERENCE_ROOT, preferenceScreen.getKey());
    fragment.setArguments(args);
    ft.add(R.id.fragment_container, fragment, preferenceScreen.getKey());
    ft.addToBackStack(preferenceScreen.getKey());
    ft.commit();
    return true;
}

MyPreferenceFragment

public class MyPreferenceFragment extends AppPreferenceFragment {

   public static final String FRAGMENT_TAG = "my_preference_fragment";

   public MyPreferenceFragment() {
   }

   @Override
   public void onCreatePreferences(Bundle bundle, String rootKey) {
       setPreferencesFromResource(R.xml.preferences, rootKey);
   }
}

AppPreferenceFragment

public abstract class AppPreferenceFragment extends PreferenceFragmentCompat {

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    // Set the default white background in the view so as to avoid transparency
      view.setBackgroundColor(
              ContextCompat.getColor(getContext(), R.color.background_material_light));

  }
}

That way when you press the back button each Fragment will be popped from the stack.

For more information see this GitHub project