Android笔记（子线程通过Handler修改UI）

2015-09-12

线程

MainThread与WorkerThread

WorkerThread里面一般不允许修改UI，而在MainThread里面又不宜进行可能产生阻塞的操作，所以会产生MainThread和WorkerThread通信的问题，就出现handler，looper来解决此问题

2015-09-13

什么是Handler

Handler,Looper（循环器）和MessageQueue的基本原理

Message(消息)------------>(通过Handler放入)------------>【消息队列】--------->（Looper取出消息）

2015-09-14

由于WorkerThread一般不允许修改UI,所以要新建Handler内部类，在WorkerThread里面调用handler方法，获取网络数据；在Handler里用handleMessage方法修改textView,在主线程中新建Handler对象.(handler就相当于一个中间工具，实现把子线程的数据传到主线程)

public class MainActivity extends Activity {

    private TextView textView;

    private Button button;

    private Handler handler;

   

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

       

        textView = (TextView)findViewById(R.id.textView);

        button = (Button)findViewById(R.id.button);

        handler = new MyHandler();

       

        button.setOnClickListener(new ButtonListener());

       

      

    }

 

 

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }

  class ButtonListener implements OnClickListener{

 

    @Override

    public void onClick(View arg0) {

        Thread thread = new NetworkThread();

        thread.start();

    }

     

  }

  class MyHandler extends Handler{

 

    @Override

    public void handleMessage(Message msg) {

        String s =(String)msg.obj;

        textView.setText(s);

    }

     

  }

    class NetworkThread extends Thread{

 

        @Override

        public void run() {

            try {

                Thread.sleep(2 * 1000);

            } catch (InterruptedException e) {

                e.printStackTrace();

            }

            String s = "从网络中获取数据";

            Message msg = handler.obtainMessage();

            msg.obj = s;

            handler.sendMessage(msg);

           

           

        }

       

       

}