Android 定时异步刷新UI

android.os.Handler handler = new android.os.Handler();private Runnable runnable = new Runnable() {    @Override    public void run() {        mainActivity.clearUI();//主线程中，更新UI        handler.postDelayed(runnable, 300);//300ms调用此方法    }};public void start() {    stop();    handler.post(runnable);}private void stop() {    handler.removeCallbacks(runnable);//移除回调}