//标识位的设定
boolean flag=false;
消息的接受，UI更新或者文本更新;
    Handler handler=new Handler(){
        @Override
        public void handleMessage(@NonNull Message msg) {
            if(msg.what==0x01){
                textView.setText((String)msg.obj);
            }
        }
    };
//UI的初始化
flag=true;
new Thread(){
            @Override
            public void run() {
                super.run();
                while(flag){
                    SimpleDateFormat format=new SimpleDateFormat("yyyy年MM月 HH:mm:ss");
                    String timeStr =format.format(System.currentTimeMillis());
                    Message msg=new Message();
                    msg.what=0x01;
                    msg.obj=timeStr;
                    handler.sendMessage(msg);
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();
线程的销毁（关闭）;
    @Override
    protected void onDestroy() {
        super.onDestroy();
        flag=false;
    }