public void onCreate(Bundle savedInstanceState) { 
   super.onCreate(savedInstanceState); 
   setContentView(R.layout.main); 
   editText = (EditText) findViewById(R.id.weather_city_edit); 
   Button button = (Button) findViewById(R.id.goQuery); 
   button.setOnClickListener(this); 

   Looper looper = Looper.myLooper();  //得到当前线程的Looper实例，由于当前线程是UI线程也可以通过Looper.getMainLooper()得到 
    messageHandler = new MessageHandler(looper);  //此处甚至可以不需要设置Looper，因为 Handler默认就使用当前线程的Looper 
}

public void onClick(View v) { 
   new Thread() { 
      public void run() { 
          Message message = Message.obtain(); 
          message.obj = "abc"; 
          messageHandler.sendMessage(message);  //发送消息
       } 
   }.start(); 
}

Handler messageHandler = new Handler { 
   public MessageHandler(Looper looper) { 
      super(looper); 
  }
   public void handleMessage(Message msg) { 
      setTitle((String) msg.obj); 
   }
}