custom current location overlay for osmdroid

CurrentLocationOverlay.java

package // ... ;
  
import org.osmdroid.views.overlay.Overlay;

final class CurrentLocationOverlay extends Overlay implements LocationListener {
  private MapView mapView;
  private LocationManager locationManager;
 
  private boolean followLocation = true;
  private String locationProvider;
  
  private boolean isLocationAvailable;
  
  public CurrentLocationOverlay(Context context, String locationProvider, MapView mapView) {
    this.mapView = mapView;
    this.locationProvider = locationProvider;
    this.locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
  }
  
  @Override
  public void onLocationChanged(Location location) {
    this.lastLocation = location;
    this.mapView.invalidate();
  }
  
  @Override
  public void onStatusChanged(String provider, int status, Bundle extras) {
    // do nothing ...
  } 
  
  @Override
  public void onProviderEnabled(String provider) {
    if(this.locationProvider.equals(provider)) {
      this.isLocationAvailable = true;
      this.mapView.invalidate();
    }
  }
  
  @Override
  public void onProviderDisabled(String provider) {
    if(this.locationProvider.equals(provider)) {
      this.isLocationAvailable = false;
      this.mapView.invalidate();
    }
  }  
  
  /*
  * draw the current location symbol always when the overlay has been invalidated.
  * the event is called thice: once for drawing the shadow and again for drawing the shape
  */
  @Override 
  public void draw(Canvas canvas, MapView mapView, boolean shadow) {
    if(!this.isEnabled() || !this.isLocationAvailable) { return; }
    
    if(shadow) {
      
    } else {
      GeoPoint geoPoint = new GeoPoint(this.lastLocation.getLatitude(), this.lastLocation.getLongitude());
      Projection projection = this.mapView.getProjection();
      
      Point screenPoint = new Point();
      projection.toPixels(geoPoint, screenPoint);
      
      Paint paint = new Paint();
      paint.setStyle(Paint.Style.FILL);
      
      // draw outer circle
      paint.setColor(Color.RED);
      canvas.drawCircle(point.getX(), point.getY(), 20, paint);
      
      // draw inner circle
      paint.setColor(Color.RED);
      canvas.drawCircle(point.getX(), point.getY(), 5, paint);
      
      // center the map again if followLocation is enabled
      if(this.followLocation) {
        IMapController mapController = this.mapView.getController();
        mapController.animateTo(geoPoint); 
      }
    }
  }
  
  /*
  * enable the location display on the map
  */
  public void enableLocation() {
    if(this.locationManager != null) {
      this.isLocationAvailable = this.locationManager.isProviderEnabled(this.locationProvider);
      
      this.locationManager.requestLocationUpdates(this.locationProvider, 100, 0.0f, this);
      this.lastLocation = this.locationManager.getLastKnownLocation(this.locationProvider);
      
      // enable drawing the overlay
      this.setEnabled(true);
      this.mapView.invalidate();
    }
  }
  
  /*
  * disable the location display on the map
  */
  public void disableLocation() {
    if(this.locationManager != null) {
      this.locationManager.removeUpdates(this);
      
      // prevent from drawing the overlay
      this.setEnabled(false);
      this.mapView.invalidate();
    }
  }
  
  public void setFollowLocation(boolean followLocation) {
    this.followLocation = followLocation; 
  }
  
  public boolean getFollowLocation() {
    return this.followLocation; 
  }
  
  public void setLocationProvider(String locationProvider) {
    this.disableLocation();
    this.locationProvider = locationProvider;
    this.enableLocation();
  }
  
  public String getLocationProvider() {
    return this.locationProvider; 
  }
}