获取帧率

参考：android.view.ViewRootImpl#draw 里的 trackFPS

public class FpsCounter {

    private static final long MONITOR_INTERVAL = 160L; //单次计算FPS使用160毫秒
    private static final long MONITOR_INTERVAL_NANOS = MONITOR_INTERVAL * 1000L * 1000L;
    private static final long MAX_INTERVAL = 1000L; //设置计算fps的单位时间间隔1000ms,即fps/s;

    private long mStartFrameTime = 0;
    private int mFrameCount = 0;

    private void getFPS() {
        Choreographer.getInstance().postFrameCallback(new Choreographer.FrameCallback() {
            @Override
            public void doFrame(long frameTimeNanos) {
                if (mStartFrameTime == 0) {
                    mStartFrameTime = frameTimeNanos;
                }
                long interval = frameTimeNanos - mStartFrameTime;
                if (interval > MONITOR_INTERVAL_NANOS) {
                    double fps = (((double) (mFrameCount * 1000L * 1000L)) / interval) * MAX_INTERVAL;
                    mFrameCount = 0;
                    mStartFrameTime = 0;
                } else {
                    ++mFrameCount;
                }

                Choreographer.getInstance().postFrameCallback(this);
            }
        });
    }
}