ac_pois_map_fragment.java

public class PoisMapFragment extends Fragment implements OnMapReadyCallback {

    private AcFragmentPoisMapBinding mBinding;

    /* Might be null if Google Play services APK is not available. */
    private GoogleMap mMap = null;
    private static final String MAPVIEW_BUNDLE_KEY = "MapViewBundleKey";
    private static final LatLng bergamo = new LatLng(45.6983, 9.6773);
    private static final LatLng rome = new LatLng(41.9028, 12.4964);


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        /* Inflate the layout for this fragment */
        mBinding = DataBindingUtil.inflate(inflater, R.layout.ac_fragment_pois_map, container, false);

        initMap(savedInstanceState);

        return mBinding.getRoot();
    }

    public void setViewModel(PoisViewModel viewModel) {
        this.mViewModel = viewModel;
    }

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

        if (getParentViewModel() != null) {
            getParentViewModel().getObservableAllPois().observe(this, list -> {
                if (list != null) {
                    Log.d(LOG_TAG, "New data received. Size: " + list.size());
                    updateMap(list);
                }
            });
        }
    }
    
    private PoisViewModel getParentViewModel() {
        if (getActivity() != null)
            return ((MainActivity) getActivity()).getViewModel();
        else
            return null;
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        this.mMap = googleMap;

        if (getParentViewModel() != null) {
            updateMap(getParentViewModel().getObservableAllPois().getValue());
        }
    }

    private void initMap(Bundle savedInstanceState) {
        Bundle mapViewBundle = null;
        if (savedInstanceState != null) {
            mapViewBundle = savedInstanceState.getBundle(MAPVIEW_BUNDLE_KEY);
        }

        mBinding.map.onCreate(mapViewBundle);
        mBinding.map.getMapAsync(this);
    }

    private void updateMap(List<Poi> pois) {
        if (mMap != null) {
            for (Poi poi : pois) {
                LatLng coords = new LatLng(poi.getLocationLat(), poi.getLocationLng());

                mMap.addMarker(new MarkerOptions().position(coords));
            }

            CameraPosition.Builder builder = new CameraPosition.Builder();
            builder.target(rome);
            builder.zoom(5f);

            CameraUpdate update = CameraUpdateFactory.newCameraPosition(builder.build());
            mMap.moveCamera(update);
        }
    }
    
    


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

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

        mBinding.map.onSaveInstanceState(mapViewBundle);
    }

    @Override
    public void onResume() {
        mBinding.map.onResume();
        super.onResume();
    }

    @Override
    public void onPause() {
        mBinding.map.onPause();
        super.onPause();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mBinding.map.onDestroy();
    }

    @Override
    public void onLowMemory() {
        super.onLowMemory();
        mBinding.map.onLowMemory();
    }
}