Handler消息传递机制(四)子线程接收主线程发送的消息

package com.example.looper;

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 {

	private Button send;
	private Handler handler;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		send = (Button) findViewById(R.id.button1);
		new Thread(new MyThread()).start();
		//主线程有一个默认的Looper
		send.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				Message message = Message.obtain();
				message.obj = "Jackson";
				handler.sendMessage(message);
			}
		});
	}
  
	public class MyThread implements Runnable{

		@Override
		public void run() {
			//在子线程没有Looper的概念
			Looper.prepare();//循环消息队列
			//在子线程实例化handler
           handler = new Handler(){
        	 @Override
        	public void handleMessage(Message msg) {
        		//子线程中接收主线程发送过来的消息
        		super.handleMessage(msg);
        		System.out.println("--从主线程获取消息-->>" + msg.obj);
        	}  
           };
           Looper.loop();
		}
	}
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.looper.MainActivity" >

    <Button
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="56dp"
        android:text="发送消息" />


</RelativeLayout>

在Logcat下查看输出的结果