OC - P7: Go4Lunch - MVVM Example for MapFragment

MapFragment.java

public class MapFragment extends SupportMapFragment {

    public static MapFragment newInstance() {
        return new MapFragment();
    }

    private MapViewModel viewModel;

    private GoogleMap googleMap;

    @SuppressLint("MissingPermission")
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        viewModel = new ViewModelProvider(this, ViewModelFactory.getInstance()).get(MapViewModel.class);
        viewModel.getViewStateLiveData().observe(getViewLifecycleOwner(), mapViewState -> {
            // Markets "stack" on top of each other, even if they are the "same", causing performance issues...
            googleMap.clear();

            for (MapMarker mapMarker : mapViewState.getMapMarkers()) {
                googleMap.addMarker(new MarkerOptions()
                    .position(
                        new LatLng(
                            mapMarker.getLatitude(),
                            mapMarker.getLongitude()
                        )
                    )
                    .title(mapMarker.getName())
                    .snippet(mapMarker.getAddress())
                );
            }
            if (mapViewState.getCameraPosition() != null) {
                googleMap.moveCamera(CameraUpdateFactory.newCameraPosition(mapViewState.getCameraPosition()));
            }
            googleMap.setMyLocationEnabled(mapViewState.isMyLocationEnabled());
            googleMap.getUiSettings().setMyLocationButtonEnabled(mapViewState.isMyLocationButtonEnabled());
        });

        getMapAsync(googleMapRef -> {
            googleMap = googleMapRef;

            initGoogleMap();
        });
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();

        viewModel.isMapAvailable(false);
    }

    private void initGoogleMap() {
        googleMap.getUiSettings().setCompassEnabled(true);
        googleMap.getUiSettings().setIndoorLevelPickerEnabled(true);
        googleMap.getUiSettings().setAllGesturesEnabled(true);

        googleMap.setOnCameraIdleListener(() ->
            viewModel.onMapCameraStabilized(googleMap.getProjection().getVisibleRegion().latLngBounds)
        );

        viewModel.isMapAvailable(true);
    }
}

MapMarker.java

public class MapMarker {

    @NonNull
    private final String placeId;

    @NonNull
    private final String name;

    @NonNull
    private final String address;

    private final double latitude;

    private final double longitude;

    public MapMarker(
        @NonNull String placeId,
        @NonNull String name,
        @NonNull String address,
        double latitude,
        double longitude
    ) {
        this.placeId = placeId;
        this.name = name;
        this.address = address;
        this.latitude = latitude;
        this.longitude = longitude;
    }

    @NonNull
    public String getPlaceId() {
        return placeId;
    }

    @NonNull
    public String getName() {
        return name;
    }

    @NonNull
    public String getAddress() {
        return address;
    }

    public double getLatitude() {
        return latitude;
    }

    public double getLongitude() {
        return longitude;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        MapMarker mapMarker = (MapMarker) o;
        return Double.compare(mapMarker.latitude, latitude) == 0 &&
            Double.compare(mapMarker.longitude, longitude) == 0 &&
            placeId.equals(mapMarker.placeId) &&
            Objects.equals(name, mapMarker.name) &&
            Objects.equals(address, mapMarker.address);
    }

    @Override
    public int hashCode() {
        return Objects.hash(placeId, name, address, latitude, longitude);
    }

    @NonNull
    @Override
    public String toString() {
        return "MapMarker{" +
            "placeId='" + placeId + '\'' +
            ", name='" + name + '\'' +
            ", address='" + address + '\'' +
            ", latitude=" + latitude +
            ", longitude=" + longitude +
            '}';
    }
}

MapViewModel.java

public class MapViewModel extends ViewModel {

    private static final float DEFAULT_ZOOM = 15f;

    // A UseCase is a layer between ViewModel and Repository. If you're unfamiliar with it, consider it's a smart Repository for now.
    @NonNull
    private final GetNearbyRestaurantsUseCase getNearbyRestaurantsUseCase;

    @NonNull
    private final MediatorLiveData<MapViewState> mapViewStateMediatorLiveData = new MediatorLiveData<>();

    @NonNull
    private final MutableLiveData<Boolean> isMapAvailableLiveData = new MutableLiveData<>();

    public MapViewModel(
        @NonNull GetNearbyRestaurantsUseCase getNearbyRestaurantsUseCase,
        @NonNull LocationRepository locationRepository
    ) {
        this.getNearbyRestaurantsUseCase = getNearbyRestaurantsUseCase;

        // Restaurants found around the user come from here
        LiveData<Collection<Restaurant>> nearbyRestaurantsLiveData = getNearbyRestaurantsUseCase.get();
        LiveData<Location> locationLiveData = locationRepository.getLocationLiveData();

        mapViewStateMediatorLiveData.addSource(nearbyRestaurantsLiveData, nearbyRestaurants ->
            combine(nearbyRestaurants, locationLiveData.getValue(), isMapAvailableLiveData.getValue())
        );

        mapViewStateMediatorLiveData.addSource(isMapAvailableLiveData, isMapAvailable ->
            combine(nearbyRestaurantsLiveData.getValue(), locationLiveData.getValue(), isMapAvailable)
        );

        mapViewStateMediatorLiveData.addSource(locationLiveData, location ->
            combine(nearbyRestaurantsLiveData.getValue(), location, isMapAvailableLiveData.getValue())
        );
    }

    public void onMapCameraStabilized(@NonNull LatLngBounds bounds) {
        double latitude = bounds.getCenter().latitude;
        double longitude = bounds.getCenter().longitude;

        // Convert the camera "zoom" to the actual distance represented on the map to show POI that user could see on its map
        float[] distance = new float[1];
        Location.distanceBetween(
            bounds.northeast.latitude,
            bounds.northeast.longitude,
            bounds.southwest.latitude,
            bounds.southwest.longitude,
            distance
        );
        int radius = (int) ((distance[0] / 2) * 0.8); // Let's take only 80% of the screen diagonal

        getNearbyRestaurantsUseCase.searchArea(latitude, longitude, radius);
    }

    public void isMapAvailable(boolean isMapAvailable) {
        isMapAvailableLiveData.setValue(isMapAvailable);
    }

    @NonNull
    public LiveData<MapViewState> getViewStateLiveData() {
        return mapViewStateMediatorLiveData;
    }

    private void combine(
        @Nullable Collection<Restaurant> restaurants,
        @Nullable Location location,
        @Nullable Boolean isMapAvailable
    ) {
        if (isMapAvailable == null) {
            // We don't know if Map (view) is ready or not, wait for its creation !
            return;
        }

        if (isMapAvailable) {
            MapViewState mapViewState = new MapViewState(
                computeMapMarkers(restaurants),
                computeCameraPosition(location),
                location != null,
                location != null
            );

            mapViewStateMediatorLiveData.setValue(mapViewState);
        } else {
            mapViewStateMediatorLiveData.setValue(null);
        }
    }

    @NonNull
    private List<MapMarker> computeMapMarkers(@Nullable Collection<Restaurant> restaurants) {
        List<MapMarker> markers = new ArrayList<>();

        if (restaurants != null) {
            for (Restaurant restaurant : restaurants) {
                markers.add(
                    new MapMarker(
                        restaurant.getPlaceId(),
                        restaurant.getName(),
                        restaurant.getAddress(),
                        restaurant.getLatitude(),
                        restaurant.getLongitude()
                    )
                );
            }
        }

        return markers;
    }

    @Nullable
    private CameraPosition computeCameraPosition(@Nullable Location location) {
        CameraPosition cameraPosition;

        if (location == null) {
            cameraPosition = null;
        } else {
            cameraPosition = CameraPosition.builder()
                .target(
                    new LatLng(
                        location.getLatitude(),
                        location.getLongitude()
                    )
                )
                .zoom(DEFAULT_ZOOM)
                .build();
        }
        return cameraPosition;
    }
}

MapViewState.java

public class MapViewState {
    @NonNull
    private final List<MapMarker> mapMarkers;

    @Nullable
    private final CameraPosition cameraPosition;

    private final boolean isMyLocationEnabled;

    private final boolean isMyLocationButtonEnabled;

    public MapViewState(
        @NonNull List<MapMarker> mapMarkers,
        @Nullable CameraPosition cameraPosition,
        boolean isMyLocationEnabled,
        boolean isMyLocationButtonEnabled
    ) {
        this.mapMarkers = mapMarkers;
        this.cameraPosition = cameraPosition;
        this.isMyLocationEnabled = isMyLocationEnabled;
        this.isMyLocationButtonEnabled = isMyLocationButtonEnabled;
    }

    @NonNull
    public List<MapMarker> getMapMarkers() {
        return mapMarkers;
    }

    @Nullable
    public CameraPosition getCameraPosition() {
        return cameraPosition;
    }

    public boolean isMyLocationEnabled() {
        return isMyLocationEnabled;
    }

    public boolean isMyLocationButtonEnabled() {
        return isMyLocationButtonEnabled;
    }

    @NonNull
    @Override
    public String toString() {
        return "MapViewState{" +
            "mapMarkers=" + mapMarkers +
            ", cameraPosition=" + cameraPosition +
            ", isMyLocationEnabled=" + isMyLocationEnabled +
            ", isMyLocationButtonEnabled=" + isMyLocationButtonEnabled +
            '}';
    }
}