Android: saving and restoring the state of a fragment

Question

I'm using a fragment (v4) inside an activity. The fragment shows a GoogleMap and I I would like to save the camera position/state of the map when the app goes into the background and restore the camera once it comes to foreground again.

android.support.v4.app.Fragment

The camera state is saved in onSaveInstanceState(Bundle) and restored in onViewStateRestored(Bundle). But I wonder if those methods are the correct one. Why? Because onSaveInstanceState is called when you switch to another activity in the same app but also when you go back to the home screen or if you start another app. Everything's fine. But the onViewStateRestored method is never ever called.

Q: So what's wrong?

public class MapFragment extends Fragment implements OnMapReadyCallback {

    private final String SAVED_CAMERA_STATE = "state_map_camera";

    private GoogleMap map;
    private CameraPosition camera;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_map, container, false);

        SupportMapFragment mapFragment = (SupportMapFragment)getChildFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

        if (savedInstanceState != null)
            camera = savedInstanceState.getParcelable(SAVED_CAMERA_STATE);
        return view;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);

        if (map == null)
            return;

        // save camera state
        outState.putParcelable(SAVED_CAMERA_STATE, map.getCameraPosition());
    }

    @Override
    public void onViewStateRestored(@Nullable Bundle savedInstanceState) {
        super.onViewStateRestored(savedInstanceState);

        if (savedInstanceState == null)
            return;

        camera = savedInstanceState.getParcelable(SAVED_CAMERA_STATE);

        // restore the camera state;
        if (map != null && camera != null)
            map.moveCamera(CameraUpdateFactory.newCameraPosition(camera));
    }

    @Override
    public void onMapReady(GoogleMap map) {

        this.map = map;

        // ToDo: add your markers to the map

        // restore the camera state
        if (camera != null) {
            map.moveCamera(CameraUpdateFactory.newCameraPosition(camera));
    }
}

I hope your problem solved through link http://stackoverflow.com/a/41256696/2291566 — Nilesh Savaliya, Dec 21 '16 at 08:40

score 0 · Accepted Answer · answered Jul 16 '15 at 17:01

0

The example from the Android documentation shows the values being restored in the fragment's onActivityCreated() method. See the example at the bottom of this page: http://developer.android.com/guide/components/fragments.html#Lifecycle.

answered Jul 16 '15 at 17:01

H-Man

81
4

True, but still save... is called all the time and restore... never. – Matthias Jul 16 '15 at 17:14
1

It is explained well here: http://stackoverflow.com/questions/24605182/android-activity-and-fragment-lifecycle-issues-in-case-of-app-minimization – H-Man Jul 16 '15 at 17:26
Thanks for the hint, but that one is saving the whole fragment and not only it's state. But good idea anyway. – Matthias Dec 22 '16 at 10:13

Android: saving and restoring the state of a fragment

1 Answers1