Hollow circle

package com.mapbox.mapboxandroiddemo.examples.javaservices;
 
import android.graphics.Color;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.widget.Toast;
 
import com.mapbox.geojson.LineString;
import com.mapbox.geojson.Point;
import com.mapbox.geojson.Polygon;
import com.mapbox.mapboxandroiddemo.R;
import com.mapbox.mapboxsdk.Mapbox;
import com.mapbox.mapboxsdk.geometry.LatLng;
import com.mapbox.mapboxsdk.maps.MapView;
import com.mapbox.mapboxsdk.maps.MapboxMap;
import com.mapbox.mapboxsdk.maps.OnMapReadyCallback;
import com.mapbox.mapboxsdk.maps.Style;
import com.mapbox.mapboxsdk.style.layers.FillLayer;
import com.mapbox.mapboxsdk.style.sources.GeoJsonSource;
import com.mapbox.turf.TurfMeta;
import com.mapbox.turf.TurfTransformation;
 
import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.fillColor;
import static com.mapbox.turf.TurfConstants.UNIT_MILES;
 
/**
* Use {@link TurfTransformation#circle(Point, double, int, String)} to draw a hollow circle
* (i.e. ring) around a center coordinate.
*/
public class TurfRingActivity extends AppCompatActivity implements MapboxMap.OnMapClickListener {
private static final String CIRCLE_GEOJSON_SOURCE_ID = "CIRCLE_GEOJSON_SOURCE_ID";
private static final String CIRCLE_LAYER_ID = "CIRCLE_LAYER_ID";
private static final int OUTER_CIRCLE_MILE_RADIUS = 1;
private static final double MILE_DIFFERENCE_BETWEEN_CIRCLES = .2;
private static final int CIRCLE_STEPS = 360;
private static final Point POINT_IN_MIDDLE_OF_CIRCLE = Point.fromLngLat(-115.150738, 36.16218);
private MapView mapView;
private MapboxMap mapboxMap;
 
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
 
// Mapbox access token is configured here. This needs to be called either in your application
// object or in the same activity which contains the mapview.
Mapbox.getInstance(this, getString(R.string.access_token));
 
// This contains the MapView in XML and needs to be called after the access token is configured.
setContentView(R.layout.activity_lab_hollow_circle);
 
mapView = findViewById(R.id.mapView);
mapView.onCreate(savedInstanceState);
 
mapView.getMapAsync(new OnMapReadyCallback() {
@Override
public void onMapReady(@NonNull MapboxMap mapboxMap) {
TurfRingActivity.this.mapboxMap = mapboxMap;
mapboxMap.setStyle(new Style.Builder()
.fromUri(Style.LIGHT)
.withSource(new GeoJsonSource(CIRCLE_GEOJSON_SOURCE_ID))
.withLayer(new FillLayer(CIRCLE_LAYER_ID, CIRCLE_GEOJSON_SOURCE_ID).withProperties(
fillColor(Color.RED)
)), new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull Style style) {
moveRing(POINT_IN_MIDDLE_OF_CIRCLE);
 
TurfRingActivity.this.mapboxMap.addOnMapClickListener(TurfRingActivity.this);
 
Toast.makeText(TurfRingActivity.this, getString(R.string.tap_on_map),
Toast.LENGTH_SHORT).show();
}
}
);
}
});
}
 
@Override
public boolean onMapClick(@NonNull LatLng point) {
moveRing(Point.fromLngLat(point.getLongitude(), point.getLatitude()));
return true;
}
 
private void moveRing(Point centerPoint) {
mapboxMap.getStyle(new Style.OnStyleLoaded() {
@Override
public void onStyleLoaded(@NonNull Style style) {
 
// Use Turf to calculate the coordinates for the outer ring of the final Polygon
Polygon outerCirclePolygon = getTurfPolygon(OUTER_CIRCLE_MILE_RADIUS, centerPoint);
 
// Use Turf to calculate the coordinates for the inner ring of the final Polygon
Polygon innerCirclePolygon = getTurfPolygon(
OUTER_CIRCLE_MILE_RADIUS - MILE_DIFFERENCE_BETWEEN_CIRCLES, centerPoint);
 
GeoJsonSource outerCircleSource = style.getSourceAs(CIRCLE_GEOJSON_SOURCE_ID);
 
if (outerCircleSource != null) {
// Use the two Polygon objects above to create the final Polygon that visually represents the ring.
outerCircleSource.setGeoJson(Polygon.fromOuterInner(
// Create outer LineString
LineString.fromLngLats(TurfMeta.coordAll(outerCirclePolygon, false)),
// Create inter LineString
LineString.fromLngLats(TurfMeta.coordAll(innerCirclePolygon, false))
));
}
}
});
}
 
private Polygon getTurfPolygon(@NonNull double radius, Point centerPoint) {
return TurfTransformation.circle(centerPoint, radius, CIRCLE_STEPS, UNIT_MILES);
}
 
// Add the mapView lifecycle to the activity's lifecycle methods
@Override
public void onResume() {
super.onResume();
mapView.onResume();
}
 
@Override
protected void onStart() {
super.onStart();
mapView.onStart();
}
 
@Override
protected void onStop() {
super.onStop();
mapView.onStop();
}
 
@Override
public void onPause() {
super.onPause();
mapView.onPause();
}
 
@Override
public void onLowMemory() {
super.onLowMemory();
mapView.onLowMemory();
}
 
@Override
protected void onDestroy() {
super.onDestroy();
if (mapboxMap != null) {
mapboxMap.removeOnMapClickListener(this);
}
mapView.onDestroy();
}
 
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
mapView.onSaveInstanceState(outState);
}
}