第80章、Handle-Message-Looper消息机制之一（从零开始学Android）

转自：http://blog.csdn.net/jianghuiquan/article/details/8641071

本章着重了解一下Handle、Message、Looper用法。

一、设计界面

　　1、布局文件

　　打开res/layout/activity_main.xml文件。
　　输入以下代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/btnmain"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="自主线程发送消息给自己" />

    <Button
        android:id="@+id/btnother"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="自其它线程发送消息至主线程" />

        <TextView
        android:id="@+id/tvmsg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="" />


</LinearLayout>

二、程序文件

　　打开“src/com.genwoxue.handlemessageloop/MainActivity.java”文件。
　　然后输入以下代码：

package com.genwoxue.handlemessageloop;

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;

public class MainActivity extends Activity{

        private static long s=0;
        private String TAG = "HandlerTest";
        private ReceiveMessageThread receiveMessageThread =null;
        private EventHandler mHandler = null;

        private Button btnMain = null;
        private Button btnOther = null;
        private TextView tvMsg = null;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            btnMain = (Button)super.findViewById(R.id.btnmain);
            btnOther = (Button)super.findViewById(R.id.btnother);
            tvMsg = (TextView)super.findViewById(R.id.tvmsg);

            btnMain.setOnClickListener(new OnClickListener(){
                @Override
                public void onClick(View v){
                     //主线程发送消息给自己
                    Looper looper = Looper.myLooper();//get the Main looper related with the main thread
                    //如果不给任何参数的话会用当前线程对应的Looper(这里就是Main Looper)为Handler里面的成员mLooper赋值
                    mHandler = new EventHandler(looper);
                    // 清除整个MessageQueue里的消息
                    mHandler.removeMessages(0);
                    String obj = "This main thread's message and received by itself!";

                    Message msg = mHandler.obtainMessage(1,1,1,obj);
                    // 将Message对象送入到main thread的MessageQueue里面
                    mHandler.sendMessage(msg);
                }
            });

            btnOther.setOnClickListener(new OnClickListener(){

                @Override
                public void onClick(View v){
                     //other线程发送消息给主线程
                    receiveMessageThread = new ReceiveMessageThread();
                    receiveMessageThread.start();
                }
            });

        }

        class EventHandler extends Handler{

            public EventHandler(Looper looper){
                super(looper);
            }

            public EventHandler(){
                super();
            }
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                Log.e(TAG, "CurrentThread id:----------+>" + Thread.currentThread().getId());
                switch(msg.what){
                case 1:
                    tvMsg.setText((String)msg.obj);
                    break;
                default:
                    Log.e(TAG,(String)msg.obj);
                    break;
                }
            }

        }

        //ReceiveMessageThread has his own message queue by execute Looper.prepare();
        class ReceiveMessageThread extends Thread {

            @Override
            public void run(){
                Looper.prepare();

                    Looper looper = Looper.getMainLooper();
                    mHandler = new EventHandler(looper);
                    mHandler.removeMessages(0);

                    s=s+1;
                    Message msg =new Message();
                    msg.what=1;
                    msg.obj= String.valueOf(s);
                    // 将Message对象送入到main thread的MessageQueue里面
                    mHandler.sendMessage(msg);
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                 Looper.loop();
            }
        }

}

三、配置文件

　　打开“AndroidManifest.xml”文件。

　　然后输入以下代码：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.genwoxue.handlemessageloop"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="15" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.genwoxue.handlemessageloop.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

　　注意：采用默认AndroidManifest.xml即可，无需额外配置。

四、运行结果