Update zoom function example with selected state

platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/ZoomFunctionSymbolLayerActivity.java

@@ -1,35 +1,46 @@
 package com.mapbox.mapboxsdk.testapp.activity.style;
 
+import android.graphics.PointF;
 import android.os.Bundle;
 import android.support.annotation.NonNull;
 import android.support.v7.app.AppCompatActivity;
 
+import com.google.gson.JsonObject;
+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.style.layers.SymbolLayer;
 import com.mapbox.mapboxsdk.style.sources.GeoJsonSource;
 import com.mapbox.mapboxsdk.testapp.R;
+import com.mapbox.services.commons.geojson.Feature;
+import com.mapbox.services.commons.geojson.FeatureCollection;
+import com.mapbox.services.commons.geojson.Point;
+import com.mapbox.services.commons.models.Position;
 
-import java.net.MalformedURLException;
-import java.net.URL;
+import java.util.List;
 
 import timber.log.Timber;
 
+import static com.mapbox.mapboxsdk.style.functions.Function.property;
 import static com.mapbox.mapboxsdk.style.functions.Function.zoom;
 import static com.mapbox.mapboxsdk.style.functions.stops.Stop.stop;
+import static com.mapbox.mapboxsdk.style.functions.stops.Stops.categorical;
 import static com.mapbox.mapboxsdk.style.functions.stops.Stops.interval;
 import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.iconAllowOverlap;
 import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.iconImage;
+import static com.mapbox.mapboxsdk.style.layers.PropertyFactory.iconSize;
 
+/**
+ * Test activity showcasing changing the icon with a zoom function and adding selection state to a SymbolLayer.
+ */
 public class ZoomFunctionSymbolLayerActivity extends AppCompatActivity {
 
-  private static final String SOURCE_URL = "https://gist.githubusercontent.com/anonymous/"
-    + "70ddad0e58520307cd1699e704f4b626/raw/a5deaccdc4517c12d63b1f8abcb7becf5e36506a/map.geojson";
   private static final String LAYER_ID = "symbolLayer";
   private static final String SOURCE_ID = "poiSource";
   private static final String BUS_MAKI_ICON_ID = "bus-11";
   private static final String CAFE_MAKI_ICON_ID = "cafe-11";
+  private static final String KEY_PROPERTY_SELECTED = "selected";
   private static final float ZOOM_STOP_MIN_VALUE = 7.0f;
   private static final float ZOOM_STOP_MAX_VALUE = 12.0f;
 
@@ -48,19 +59,30 @@ public void onCreate(Bundle savedInstanceState) {
       @Override
       public void onMapReady(@NonNull final MapboxMap map) {
         mapboxMap = map;
-        addSource();
+        updateSource(false);
         addLayer();
+        addMapClickListener();
       }
     });
   }
 
-  private void addSource() {
-    try {
-      source = new GeoJsonSource(SOURCE_ID, new URL(SOURCE_URL));
-    } catch (MalformedURLException exception) {
-      Timber.e(exception, "That's not an url... ");
+  private void updateSource(boolean selected) {
+    FeatureCollection featureCollection = createFeatureCollection(selected);
+    if (source != null) {
+      source.setGeoJson(featureCollection);
+    } else {
+      source = new GeoJsonSource(SOURCE_ID, featureCollection);
+      mapboxMap.addSource(source);
     }
-    mapboxMap.addSource(source);
+  }
+
+  private FeatureCollection createFeatureCollection(boolean selected) {
+    Point point = Point.fromCoordinates(Position.fromCoordinates(-74.016181, 40.701745));
+    Feature feature = Feature.fromGeometry(point);
+    JsonObject properties = new JsonObject();
+    properties.addProperty(KEY_PROPERTY_SELECTED, selected);
+    feature.setProperties(properties);
+    return FeatureCollection.fromFeatures(new Feature[] {feature});
   }
 
   private void addLayer() {
@@ -74,11 +96,37 @@ private void addLayer() {
           )
         )
       ),
+      iconSize(
+        property(
+          KEY_PROPERTY_SELECTED,
+          categorical(
+            stop(true, iconSize(3.0f)),
+            stop(false, iconSize(1.0f))
+          )
+        )
+      ),
       iconAllowOverlap(true)
     );
     mapboxMap.addLayer(layer);
   }
 
+  private void addMapClickListener() {
+    mapboxMap.setOnMapClickListener(new MapboxMap.OnMapClickListener() {
+      @Override
+      public void onMapClick(@NonNull LatLng point) {
+        PointF screenPoint = mapboxMap.getProjection().toScreenLocation(point);
+        List<Feature> featureList = mapboxMap.queryRenderedFeatures(screenPoint, LAYER_ID);
+        if (!featureList.isEmpty()) {
+          Feature feature = featureList.get(0);
+          boolean isSelected = feature.getBooleanProperty(KEY_PROPERTY_SELECTED);
+          updateSource(!isSelected);
+        } else {
+          Timber.e("No features found");
+        }
+      }
+    });
+  }
+
   @Override
   protected void onStart() {
     super.onStart();