From 2d527c2af7224d03429b8b2ccb7c1712e8ffe12b Mon Sep 17 00:00:00 2001
From: Kevin Li <kevin.li@mapbox.com>
Date: Wed, 12 Dec 2018 09:15:55 +0800
Subject: [Android] Add setPreferredFramesPerSecond for MapView (#13498)

* [Android] Add setPreferredFramesPerSecond for MapView
---
 .../java/com/mapbox/mapboxsdk/maps/MapView.java    | 12 ++++++++
 .../mapboxsdk/maps/renderer/MapRenderer.java       | 34 +++++++++++++++++-----
 2 files changed, 38 insertions(+), 8 deletions(-)

(limited to 'platform/android/MapboxGLAndroidSDK')

diff --git a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/MapView.java b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/MapView.java
index 83948efe4c..cc1ffbbd3d 100644
--- a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/MapView.java
+++ b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/MapView.java
@@ -421,6 +421,18 @@ public class MapView extends FrameLayout implements NativeMapView.ViewCallback {
     }
   }
 
+  /**
+   *  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>
diff --git a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/renderer/MapRenderer.java b/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/renderer/MapRenderer.java
index 9617f94fce..a9bea97836 100644
--- a/platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/maps/renderer/MapRenderer.java
+++ b/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 @@ public abstract class MapRenderer implements MapRendererScheduler {
 
   @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 @@ public abstract class MapRenderer implements MapRendererScheduler {
 
   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;
   }
 }
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