Handler消息传递机制(四)子线程接收主线程发送的消息

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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;@Overrideprotected 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Loopersend.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {Message message = Message.obtain();message.obj = "Jackson";handler.sendMessage(message);}});}  public class MyThread implements Runnable{@Overridepublic 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

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