MapViewExample.java

public class ExampleActivity extends AppCompatActivity implements OnMapReadyCallback {

    private MapViewObserver mapView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_estimate);
        MapView view = findViewById(R.id.map_view);
        mapView = new MapViewObserver(getLifecycle(), view, this);
        mapView.onCreate(savedInstanceState);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        // do whatever
    }

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

}

MapViewOberver.java

public class MapViewObserver implements LifecycleObserver {

    private static final String MAPVIEW_BUNDLE_KEY = "MapViewBundleKey";

    private final MapView mapView;
    private final Lifecycle lifecycle;
    private final OnMapReadyCallback callback;

    public MapViewObserver(@NonNull Lifecycle lifecycle,
                           @NonNull MapView mapView,
                           @NonNull OnMapReadyCallback callback) {

        this.lifecycle = Preconditions.checkNotNull(lifecycle);
        this.mapView = Preconditions.checkNotNull(mapView);
        this.callback = Preconditions.checkNotNull(callback);
        lifecycle.addObserver(this);
    }

    public void onCreate(Bundle bundle) {
        Bundle mapViewBundle = null;
        if (bundle != null) {
            mapViewBundle = bundle.getBundle(MAPVIEW_BUNDLE_KEY);
        }
        mapView.onCreate(mapViewBundle);
        mapView.getMapAsync(callback);
    }

    public void onSaveInstance(Bundle bundle) {
        Bundle mapViewBundle = bundle.getBundle(MAPVIEW_BUNDLE_KEY);

        if (mapViewBundle == null) {
            mapViewBundle = new Bundle();
            bundle.putBundle(MAPVIEW_BUNDLE_KEY, mapViewBundle);
        }

        mapView.onSaveInstanceState(mapViewBundle);
    }

    @OnLifecycleEvent(value = Lifecycle.Event.ON_RESUME)
    void onResume() {
        mapView.onResume();
    }

    @OnLifecycleEvent(value = Lifecycle.Event.ON_START)
    void onStart() {
        mapView.onStart();
    }

    @OnLifecycleEvent(value = Lifecycle.Event.ON_STOP)
    void onStop() {
        mapView.onStop();
    }

    @OnLifecycleEvent(value = Lifecycle.Event.ON_PAUSE)
    void onPause() {
        mapView.onPause();
    }

    @OnLifecycleEvent(value = Lifecycle.Event.ON_DESTROY)
    void onDestroy() {
        mapView.onDestroy();
        lifecycle.removeObserver(this);
    }
}