[ios, android] Add methods to remove a custom layer

platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/MainActivity.java

@@ -76,6 +76,7 @@ public class MainActivity extends AppCompatActivity {
     private int mSelectedStyle = R.id.actionStyleMapboxStreets;
     private NavigationView mNavigationView;
     private CoordinatorLayout mCoordinatorLayout;
+    private boolean mIsShowingCustomLayer;
 
     // Used for GPS
     private FloatingActionButton mLocationFAB;
@@ -397,7 +398,11 @@ public class MainActivity extends AppCompatActivity {
                                 return true;
 
                             case R.id.action_custom_layer:
-                                addCustomLayer();
+                                if (mIsShowingCustomLayer) {
+                                    removeCustomLayer();
+                                } else {
+                                    addCustomLayer();
+                                }
                                 return true;
 
                             default:
@@ -576,6 +581,7 @@ public class MainActivity extends AppCompatActivity {
     }
 
     private void addCustomLayer() {
+        mIsShowingCustomLayer = true;
         mMapView.addCustomLayer(
             new CustomLayer("custom",
                 ExampleCustomLayer.createContext(),
@@ -585,6 +591,11 @@ public class MainActivity extends AppCompatActivity {
             null);
     }
 
+    private void removeCustomLayer() {
+        mIsShowingCustomLayer = false;
+        mMapView.removeCustomLayer("custom");
+    }
+
     // Called when FPS changes
     private class MyOnFpsChangedListener implements MapView.OnFpsChangedListener {