Adding example of using TurfTransformation#circle to create visual ring

MapboxAndroidDemo/src/global/java/com/mapbox/mapboxandroiddemo/MainActivity.java

@@ -74,6 +74,7 @@
 import com.mapbox.mapboxandroiddemo.examples.javaservices.SimplifyPolylineActivity;
 import com.mapbox.mapboxandroiddemo.examples.javaservices.StaticImageActivity;
 import com.mapbox.mapboxandroiddemo.examples.javaservices.TilequeryActivity;
+import com.mapbox.mapboxandroiddemo.examples.javaservices.TurfRingActivity;
 import com.mapbox.mapboxandroiddemo.examples.labs.AnimatedImageGifActivity;
 import com.mapbox.mapboxandroiddemo.examples.labs.AnimatedMarkerActivity;
 import com.mapbox.mapboxandroiddemo.examples.labs.CalendarIntegrationActivity;
@@ -934,6 +935,15 @@ private void initializeModels() {
       null,
       R.string.activity_java_services_tilequery_url, false, BuildConfig.MIN_SDK_VERSION));
 
+    exampleItemModels.add(new ExampleItemModel(
+      R.id.nav_java_services,
+      R.string.activity_java_turf_ring_title,
+      R.string.activity_java_turf_ring_description,
+      new Intent(MainActivity.this, TurfRingActivity.class),
+      null,
+      R.string.activity_java_turf_ring_url, false, BuildConfig.MIN_SDK_VERSION
+    ));
+
     exampleItemModels.add(new ExampleItemModel(
       R.id.nav_snapshot_image_generator,
       R.string.activity_image_generator_snapshot_notification_title,

MapboxAndroidDemo/src/main/AndroidManifest.xml

@@ -773,6 +773,14 @@
             android:name="android.support.PARENT_ACTIVITY"
             android:value="com.mapbox.mapboxandroiddemo.MainActivity" />
         </activity>
+        <activity
+            android:name=".examples.javaservices.TurfRingActivity"
+            android:label="@string/activity_java_turf_ring_title"
+            android:screenOrientation="portrait">
+            <meta-data
+                android:name="android.support.PARENT_ACTIVITY"
+                android:value="com.mapbox.mapboxandroiddemo.MainActivity" />
+        </activity>
         <activity
             android:name=".examples.labs.ValueAnimatorIconAnimationActivity"
             android:label="@string/activity_lab_animated_interpolator_icon_drop_title"

MapboxAndroidDemo/src/main/java/com/mapbox/mapboxandroiddemo/examples/javaservices/TurfRingActivity.java

@@ -0,0 +1,166 @@
+package com.mapbox.mapboxandroiddemo.examples.javaservices;
+
+import android.graphics.Color;
+import android.os.Bundle;
+import android.support.annotation.NonNull;
+import android.support.v7.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 OUTER_CIRCLE_GEOJSON_SOURCE_ID = "OUTER_CIRCLE_GEOJSON_SOURCE_ID";
+  private static final String INNER_CIRCLE_GEOJSON_SOURCE_ID = "INNER_CIRCLE_GEOJSON_SOURCE_ID";
+  private static final String OUTER_CIRCLE_LAYER_ID = "OUTER_CIRCLE_LAYER_ID";
+  private static final String INNER_CIRCLE_LAYER_ID = "INNER_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()
+            .fromUrl(Style.LIGHT)
+            .withSource(new GeoJsonSource(OUTER_CIRCLE_GEOJSON_SOURCE_ID))
+            .withSource(new GeoJsonSource(INNER_CIRCLE_GEOJSON_SOURCE_ID))
+            .withLayer(new FillLayer(OUTER_CIRCLE_LAYER_ID, OUTER_CIRCLE_GEOJSON_SOURCE_ID).withProperties(
+              fillColor(Color.RED)
+            ))
+            .withLayer(new FillLayer(INNER_CIRCLE_LAYER_ID, INNER_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) {
+    if (mapboxMap.getStyle() != null) {
+      Style style = mapboxMap.getStyle();
+
+      // 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(OUTER_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();
+    mapView.onDestroy();
+  }
+
+  @Override
+  protected void onSaveInstanceState(Bundle outState) {
+    super.onSaveInstanceState(outState);
+    mapView.onSaveInstanceState(outState);
+  }
+}

MapboxAndroidDemo/src/main/res/layout/activity_lab_hollow_circle.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:mapbox="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".examples.labs.SpaceStationLocationActivity">
+
+    <com.mapbox.mapboxsdk.maps.MapView
+        android:id="@+id/mapView"
+        android:layout_width="match_parent"
+        mapbox:mapbox_cameraTargetLat=" 36.16218"
+        mapbox:mapbox_cameraTargetLng="-115.150738"
+        mapbox:mapbox_cameraZoom="11"
+        android:layout_height="match_parent"/>
+
+</RelativeLayout>

MapboxAndroidDemo/src/main/res/values/activity_strings.xml

@@ -333,4 +333,7 @@
 
     <!-- Polygon toggle -->
     <string name="tap_on_neighborhood">Tap on a neighborhood area to toggle its color</string>
+
+    <!-- Turf circle ring-->
+    <string name="tap_on_map">Tap on the map to move the ring</string>
 </resources>

MapboxAndroidDemo/src/main/res/values/descriptions_strings.xml

@@ -117,4 +117,5 @@
     <string name="activity_dds_polygon_select_toggle_description">Tap on various polygons to "select" them and toggle their colors.</string>
     <string name="activity_china_simple_china_mapview_description">Show an accurate and government-approved China map in your app using the Mapbox Maps SDK.</string>
     <string name="activity_lab_home_screen_widget_description">Show the device\'s current location or other information in a homescreen widget.</string>
+    <string name="activity_java_turf_ring_description">Use Turf to calculate coordinates to eventually draw a ring around a center coordinate.</string>
 </resources>

MapboxAndroidDemo/src/main/res/values/titles_strings.xml

@@ -115,4 +115,5 @@
     <string name="activity_dds_polygon_select_toggle_title">Polygon toggle</string>
     <string name="activity_china_simple_china_mapview_title">China map view</string>
     <string name="activity_lab_home_screen_widget_title">Homescreen geocoding widget</string>
+    <string name="activity_java_turf_ring_title">Hollow circle</string>
 </resources>

MapboxAndroidDemo/src/main/res/values/urls_strings.xml

@@ -117,4 +117,5 @@
     <string name="activity_dds_polygon_select_toggle_url" translatable="false">https://i.imgur.com/gVIfE3G.png</string>
     <string name="activity_china_simple_china_mapview_url" translatable="false">https://i.imgur.com/KwoEynZ.png</string>
     <string name="activity_lab_home_screen_widget_url" translatable="false">https://i.imgur.com/H5N9jDn.png</string>
+    <string name="activity_java_turf_ring_url" translatable="false">https://i.imgur.com/nG8xeXH.png</string>
 </resources>