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环境：
cocos creator 2.4.3
华为meta 50

背景：
小游戏 需要在update 里取帧率 发现跟时间对不上
游戏设置60帧
手机上显示 90帧
cc.game.setFrameRate(30) 显示 30帧
cc.game.setFrameRate(60) 显示 90帧

结论：
对于老版本的cocos creator 如果有依赖帧率的逻辑
需要自行注意逻辑正确性
cc.game.getFrameRate() 取出来的帧率 有可能 并不是当前真实帧率 只是逻辑帧率

源码分析：

	cocos2dxRenderer.java @Overridepublic void onDrawFrame(final GL10 gl) {if (mNeedToPause)return;if (mNeedShowFPS) {///IDEA: show FPS in Android Text control rather than outputing log.++mFrameCount;long nowFpsTime = System.nanoTime();long fpsTimeInterval = nowFpsTime - mOldNanoTime;if (fpsTimeInterval > 1000000000L) {double frameRate = 1000000000.0 * mFrameCount / fpsTimeInterval;Cocos2dxHelper.OnGameInfoUpdatedListener listener = Cocos2dxHelper.getOnGameInfoUpdatedListener();if (listener != null) {listener.onFPSUpdated((float) frameRate);}mFrameCount = 0;mOldNanoTime = System.nanoTime();}/}/** No need to use algorithm in default(60 FPS) situation,* since onDrawFrame() was called by system 60 times per second by default.*/if (sAnimationInterval <= INTERVAL_60_FPS) {Cocos2dxRenderer.nativeRender();} else {final long now = System.nanoTime();final long interval = now - this.mLastTickInNanoSeconds;if (interval < Cocos2dxRenderer.sAnimationInterval) {try {Thread.sleep((Cocos2dxRenderer.sAnimationInterval - interval) / Cocos2dxRenderer.NANOSECONDSPERMICROSECOND);} catch (final Exception e) {}}/** Render time MUST be counted in, or the FPS will slower than appointed.*/this.mLastTickInNanoSeconds = System.nanoTime();Cocos2dxRenderer.nativeRender();}}

分析上述代码

if (sAnimationInterval <= INTERVAL_60_FPS) {Cocos2dxRenderer.nativeRender();
}

说明 >= 60帧的设置 。没有处理刷新帧率 走的系统是高刷
所以会导致 dt 并不是 60帧的dt