Looper.prepare();//步骤1，线程里使用handler必须这样写，

             handler = new Handler(){//步骤2，先实例化handler

                 @Override

                 public void handleMessage(Message msg) {

                     String receiver = msg.obj.toString();

                     System.out.println("receiver:"+receiver+","+Thread.currentThread().getName());

                 }

             };

             Looper.loop();//步骤3 ，循环Looper

 package com.wyl.handler_mars;

 import android.app.Activity;

 import android.os.Bundle;

 import android.os.Handler;

 import android.os.Looper;

 import android.os.Message;

 import android.util.Log;

 import android.view.View;

 import android.view.View.OnClickListener;

 import android.widget.Button;

 import android.widget.TextView;

 import android.widget.Toast;

 /**

  * 主线程发送消息，工作线程接收消息

  * @author Wyl

  *

  */

 public class SecondActivity extends Activity implements OnClickListener{

     Button btn_fasong;

     Handler hand;

     Message msg;

     TextView tv;

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         // TODO Auto-generated method stub

         super.onCreate(savedInstanceState);

         setContentView(R.layout.main2);

         btn_fasong = (Button) findViewById(R.id.btn_send);

         tv = (TextView) findViewById(R.id.tv_01);

         btn_fasong.setOnClickListener(this);

         Thread t = new MyThread();

         t.start();

     }

     @Override

     public void onClick(View v) {

         //hand = new Handler();//这一行尤其重要，如果不注释掉，那么下面的线程中就没法接收到消息，因为这行代码中又重新生成了一个handler对象，也就对应着不同的looper，所以就没法

         Message msg = hand.obtainMessage();

         msg.obj = "无语了。。。";

         System.out.println("onClick()...发送："+"无语了。。。");

         hand.sendMessage(msg);//主线程发送消息

     }

     class MyThread extends Thread{

         @Override

         public void run() {

             Looper.prepare();//获取一个Looper对象

             System.out.println("===========");

             hand = new Handler(){

                 @Override

                 public void handleMessage(Message msg) {

                     // TODO Auto-generated method stub

                     System.out.println("MyThread.run()接收到了消息"+",所在线程："+Thread.currentThread().getName());

                 }

             };

             Looper.loop();

         }

     }

 }

 <?xml version="1.0" encoding="utf-8"?>

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

     android:layout_width="fill_parent"

     android:layout_height="fill_parent"

     android:orientation="vertical" >

     <Button

         android:id="@+id/btn_send"

         android:onClick="doClick"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:hint="发送" />

     <Button

         android:id="@+id/btn_Cancel"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:hint="取消发送" />

 </LinearLayout>

 package com.wyl.handler;

 import android.app.Activity;

 import android.os.Bundle;

 import android.os.Handler;

 import android.os.Looper;

 import android.os.Message;

 import android.view.View;

 import android.view.View.OnClickListener;

 import android.widget.Button;

 public class MainActivity extends Activity{

     Button btn_fs;//发送

     Button btn_qx;//取消

     Handler handler;

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.main);

         btn_fs = (Button) findViewById(R.id.btn_send);

         btn_qx = (Button) findViewById(R.id.btn_Cancel);

         btn_fs.setOnClickListener(new OnClickListener() {

             @Override

             public void onClick(View v) {

                 Message msg = handler.obtainMessage();

                 String str = "我是wyl";

                 msg.obj = str;

                 System.out.println("onClick()发送："+str+","+Thread.currentThread().getName());

                 handler.sendMessage(msg);

             }

         });

         /*

          * 这个线程里的handler在onClick()方法之前使用到，所以需要在线程的run()方法里

          * 实例化，onClick()方法里就不用实例化了，也不能怪进行重新实例化，否则又是实例化的

          * handler对象就不是一个了，handler不一致的话就会导致循环的队列不是同一个，就会

          * 导致workThread里的handleMessage()方法没法接收到UIThread发出的消息

          */

         MyThread t = new MyThread();

         t.start();

     }

     class MyThread extends Thread{

         @Override

         public void run() {

             Looper.prepare();//步骤1，线程里使用handler必须这样写，

             handler = new Handler(){//步骤2，先实例化handler

                 @Override

                 public void handleMessage(Message msg) {

                     String receiver = msg.obj.toString();

                     System.out.println("receiver:"+receiver+","+Thread.currentThread().getName());

                 }

             };

             Looper.loop();//步骤3 ，循环Looper

         }

     }

 }