绘制原理

CPU负责计算显示内容

GPU负责栅格化（UI元素绘制到屏幕上）

16ms发出VSync信号触发UI渲染

大多数的Android设备屏幕刷新频率：60HZ

优化工具

Systrace

关注Frames

正常：绿色圆点 ， 丢帧：黄色或红色

Alerts栏

Layout Inspector

AndroidStudio自带工具

查看视图层次结构

Choreographer

获取FPS,线上使用，具备实时性

Api16之后

private long mStartFrameTime = 0;
    private int mFrameCount = 0;
    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;
    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    private void getFPS() {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
            return;
        }
        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);
            }
        });
    }