[Android] Add setPreferredFramesPerSecond for MapView (#13498)

* [Android] Add setPreferredFramesPerSecond for MapView

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/MapView.java

@@ -421,6 +421,18 @@ public void onDestroy() {
     }
   }
 
+  /**
+   *  The maximum frame rate at which the map view is rendered,
+   *  but it can't excess the ability of device hardware.
+   *
+   * @param maximumFps  Can be set to arbitrary integer values.
+   */
+  public void setMaximumFps(int maximumFps) {
+    if (mapRenderer != null) {
+      mapRenderer.setMaximumFps(maximumFps);
+    }
+  }
+
   /**
    * Returns if the map has been destroyed.
    * <p>

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/renderer/MapRenderer.java

@@ -27,6 +27,7 @@ public abstract class MapRenderer implements MapRendererScheduler {
   // Holds the pointer to the native peer after initialisation
   private long nativePtr = 0;
 
+  private double expectedRenderTime = 0;
   private MapboxMap.OnFpsChangedListener onFpsChangedListener;
 
   public MapRenderer(@NonNull Context context, String localIdeographFontFamily) {
@@ -75,11 +76,20 @@ protected void onSurfaceChanged(@NonNull GL10 gl, int width, int height) {
 
   @CallSuper
   protected void onDrawFrame(GL10 gl) {
+    long startTime = System.nanoTime();
     try {
       nativeRender();
     } catch (java.lang.Error error) {
       Logger.e(TAG, error.getMessage());
     }
+    long renderTime = System.nanoTime() - startTime;
+    if (renderTime < expectedRenderTime) {
+      try {
+        Thread.sleep((long) ((expectedRenderTime - renderTime) / 1E6));
+      } catch (InterruptedException ex) {
+        Logger.e(TAG, ex.getMessage());
+      }
+    }
     if (onFpsChangedListener != null) {
       updateFps();
     }
@@ -115,18 +125,26 @@ private native void nativeInitialize(MapRenderer self,
 
   private native void nativeRender();
 
-  private long frames;
   private long timeElapsed;
 
   private void updateFps() {
-    frames++;
     long currentTime = System.nanoTime();
-    double fps = 0;
-    if (currentTime - timeElapsed >= 1) {
-      fps = frames / ((currentTime - timeElapsed) / 1E9);
-      onFpsChangedListener.onFpsChanged(fps);
-      timeElapsed = currentTime;
-      frames = 0;
+    double fps = 1E9 / ((currentTime - timeElapsed));
+    onFpsChangedListener.onFpsChanged(fps);
+    timeElapsed = currentTime;
+  }
+
+  /**
+   * The max frame rate at which this render is rendered,
+   * but it can't excess the ability of device hardware.
+   *
+   * @param maximumFps Can be set to arbitrary integer values.
+   */
+  public void setMaximumFps(int maximumFps) {
+    if (maximumFps <= 0) {
+      // Not valid, just return
+      return;
     }
+    expectedRenderTime = 1E9 / maximumFps;
   }
 }

platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/maplayout/DebugModeActivity.java

@@ -63,6 +63,7 @@ protected void onCreate(Bundle savedInstanceState) {
     setupMapView(savedInstanceState);
     setupDebugChangeView();
     setupStyleChangeView();
+    setupFpsChangeView();
   }
 
   private void setupToolbar() {
@@ -172,6 +173,15 @@ private void setupStyleChangeView() {
     });
   }
 
+  private void setupFpsChangeView() {
+    findViewById(R.id.fps_30).setOnClickListener(view -> {
+      mapView.setMaximumFps(30);
+    });
+    findViewById(R.id.fps_60).setOnClickListener(view -> {
+      mapView.setMaximumFps(60);
+    });
+  }
+
   @Override
   public boolean onOptionsItemSelected(MenuItem item) {
     return actionBarDrawerToggle.onOptionsItemSelected(item) || super.onOptionsItemSelected(item);

platform/android/MapboxGLAndroidSDKTestApp/src/main/res/layout/activity_debug_mode.xml

@@ -71,6 +71,29 @@
             app:layout_anchor="@id/bottom_sheet"
             app:layout_anchorGravity="bottom|end"/>
 
+        <Button
+            android:id="@+id/fps_60"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="end|start"
+            app:backgroundTint="@color/primary"
+            android:layout_margin="@dimen/fab_margin"
+            android:text="@string/fps60"
+            app:layout_anchor="@id/bottom_sheet"
+            app:layout_anchorGravity="top|end"/>
+
+        <Button
+            android:id="@+id/fps_30"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="top|end"
+            android:layout_marginBottom="82dp"
+            app:backgroundTint="@color/primary"
+            android:layout_marginEnd="@dimen/fab_margin"
+            android:layout_marginRight="@dimen/fab_margin"
+            android:text="@string/fps30"
+            app:layout_anchor="@id/fps_60"
+            app:layout_anchorGravity="top"/>
     </android.support.design.widget.CoordinatorLayout>
 
     <android.support.design.widget.NavigationView

platform/android/MapboxGLAndroidSDKTestApp/src/main/res/values/strings.xml

@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="app_name">Mapbox Android SDK TestApp</string>
+    <string name="fps30">fps30</string>
+    <string name="fps60">fps60</string>
 </resources>