2017.12.18 Android开发之消息队列（实现子线程修改UI组件）

 private Button button;
    private Handler handler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button=(Button)findViewById(R.id.button);
        button.setOnClickListener(new ButtonListener());
        handler=new FirstHandler();
    }

    class ButtonListener implements View.OnClickListener{  //设置监听器，使得每点一次按钮生成一次消息
        @Override
        public void onClick(View view) {
            Message msg=handler.obtainMessage();
            msg.what=8;                    //msg的其中一个参数，可以设置很多msg的参数
            handler.sendMessage(msg);     //把消息扔出去
        }
    }

    class FirstHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {     //处理消息，传一个消息体进来，理解为一个对象，可以是字符串，int型之类的
            int what=msg.what;
            System.out.println("数据what是："+what);


            super.handleMessage(msg);
        }
    }

 class MyHandler extends Handler{
    @Override
    public void handleMessage(Message msg) {
        System.out.println("这是来自MyHandler的信息："+Thread.currentThread().getName());
        String s=(String)msg.obj;
        textview.setText(s);
        super.handleMessage(msg);
    }
}
    class ButtonListener implements View.OnClickListener{
        @Override
        public void onClick(View view) {
            Thread thread=new NetWorkThread();
            thread.start();
        }
    }

    class NetWorkThread extends Thread{
        @Override
        public void run() {
            System.out.println("来自NetWorkThread的信息："+Thread.currentThread().getName());
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            String s="有理想的爱国青年";
            Message msg=handler.obtainMessage();
            msg.obj=s;
            handler.sendMessage(msg);

            super.run();
        }
    }