Android handler.obtainMessage()传字符串用法

public class MainActivity extends Activity implements Runnable  {

  private TextView tv;

  Thread mthread;

  Message message;

  @Override

  protected void onCreate(Bundle savedInstanceState)

  {

    mthread=new Thread(this);

    mthread.start();//开启线程

  }

  @Override  

  public void run()  

  {    

    message = handler.obtainMessage();//性能优化后

    message.what=111;  

    message.obj = "12345678";

    handler.sendMessage(message); //发送消息

  }

  private Handler handler = new Handler()

    {

      public void handleMessage(Message msg)

      {
        super.handleMessage(msg);
        switch (msg.what)
       {
         case 111://接收消息

         tv.setText((String)msg.obj);

         Log.e("xxx",(String)msg.obj);

         break;
     }

      };

    };

}