Android消息处理Handler与Message

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1、消息Handle

Activity中UI组件中的信息传递Handler，相信很多朋友都知道，Android为了线程安全，并不允许我们在UI线程外操作UI；很多时候我们做界面刷新都需要通过Handler来通知UI组件更新！除了用Handler完成界面更新外，还可以使用runOnUiThread()来更新，甚至更高级的事务总线。

一、handler的使用场景为么会有handler？（部分内容图片摘自http://www.runoob.com/w3cnote/android-tutorial-handler-message.html）

　　二、handler的消息处理机制

　　在Android中提供了一种异步回调机制Handler,使用它，我们可以在完成一个很长时间的任务后做出相应的通知。

UI线程:就是我们的主线程,系统在创建UI线程的时候会初始化一个Looper对象,同时也会创建一个与其关联的MessageQueue;
Handler:作用就是发送与处理信息,如果希望Handler正常工作,在当前线程中要有一个Looper对象
Message:Handler接收与处理的消息对象
MessageQueue:消息队列,先进先出管理Message,在初始化Looper对象时会创建一个与之关联的MessageQueue;
Looper:每个线程只能够有一个Looper,管理MessageQueue,不断地从中取出Message分发给对应的Handler处理！

　　通俗一点讲：当我们的子线程想修改Activity中的UI组件时,我们可以新建一个Handler对象,通过这个对象向主线程发送信息;而我们发送的信息会先到主线程的MessageQueue进行等待,由Looper按先入先出顺序取出,再根据message对象的what属性分发给对应的Handler进行处理！

2、服务端：

import android.app.Service;import android.content.Intent;import android.os.Bundle;import android.os.Handler;import android.os.IBinder;import android.os.Message;import android.os.Messenger;import android.os.RemoteException;import java.sql.Date;import java.text.SimpleDateFormat;import static com.xxx.zqLog.ZqLog.logger;public class PileService extends Service {    // 6秒开始更新    private static final int UPDATE_TIMER = 1000 * 6;    private static final String TAG_MODULE_PILE = "xxx服务模块：";    private static final int RECEIVE_MESSAGE_CODE = 0x0001;    private static final int SEND_MESSAGE_CODE = 0x0002;    private Messenger clientMessenger = null;    private Messenger serviceMessenger = new Messenger(new ServiceHandler());    private class ServiceHandler extends Handler {        @Override        public void handleMessage(Message msg) {            logger.debug(TAG_MODULE_PILE + "消息服务：消息队列");            if(msg.what == RECEIVE_MESSAGE_CODE){                Bundle data = msg.getData();                if(data != null){                    String str = data.getString("msg");                    logger.debug(TAG_MODULE_PILE + "消息服务：收到客户端如下信息: " + str);                }                clientMessenger = msg.replyTo;                if(clientMessenger != null){                    SimpleDateFormat formatter = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");                    logger.debug(TAG_MODULE_PILE + "接收消息时间：" + formatter.format(new Date(System.currentTimeMillis())));                    //模拟耗时                    try {                        Thread.sleep(UPDATE_TIMER);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    logger.debug(TAG_MODULE_PILE + UPDATE_TIMER + "秒后" + "服务向客户端回信");                    logger.debug(TAG_MODULE_PILE + "发送消息时间：" + formatter.format(new Date(System                            .currentTimeMillis())));                    Message msgToClient = Message.obtain();                    msgToClient.what = SEND_MESSAGE_CODE;                    //可以通过Bundle发送跨进程的信息                    Bundle bundle = new Bundle();                    bundle.putString("xxxInformations", getJsonFromInfo());                    msgToClient.setData(bundle);                    try{                        clientMessenger.send(msgToClient);                    }catch (RemoteException e){                        e.printStackTrace();                        logger.debug(TAG_MODULE_PILE + "服务端向客户端发送信息失败: " + e.getMessage());                    }                }            }        }    }    @Override    public void onCreate() {        logger.debug(TAG_MODULE_PILE + "消息服务创建");        super.onCreate();    }    @Override    public IBinder onBind(Intent intent) {        logger.debug(TAG_MODULE_PILE + "消息服务创建连接");        return serviceMessenger.getBinder();    }    @Override    public void onDestroy() {        logger.debug(TAG_MODULE_PILE + "消息服务创建销毁");        clientMessenger = null;        super.onDestroy();    }

    private String getJsonFromxxxInfo() {        String json;        json = "{\"cc\":\"20\",\"mm\":\"ll\",\"id\":\"20173333\"," +                "\"ss\":\"message\"}";        return json;    }}

AndroidManifest.xml文件：

<application    android:allowBackup="true"    android:label="@string/app_name"    android:supportsRtl="true">    <service        android:name="com.xxx.pileservice.PileService"        android:enabled="true"        android:exported="true">        <intent-filter>            <action android:name="com.xxx.pileservice.PileService"/>            <category android:name="android.intent.category.DEFAULT"/>        </intent-filter>    </service></application>

3、客户端：

/** * 消息处理 */private static final int SEND_MESSAGE_CODE = 0x0001;private static final int RECEIVE_MESSAGE_CODE = 0x0002;private boolean isBound = false;private final String SERVICE_ACTION = "com.xxx.modulepileservice.PileService";private Messenger serviceMessenger = null;private Messenger clientMessenger = new Messenger(new ClientHandler());//客户端用ClientHandler接收并处理来自于Service的消息private class ClientHandler extends Handler {    @Override    public void handleMessage(Message msg) {        logger.debug(TAG_PROVIDER + "客户端消息队列：");        if (msg.what == RECEIVE_MESSAGE_CODE) {            Bundle data = msg.getData();            if (data != null) {                String str = data.getString("Informations");                logger.debug(TAG_PROVIDER + "客户端收到Service的消息: " + str);            }        }    }}private ServiceConnection conn = new ServiceConnection() {    @Override    public void onServiceConnected(ComponentName name, IBinder binder) {        logger.debug(TAG_PROVIDER + "客户端已连接！");        serviceMessenger = new Messenger(binder);        isBound = true;        Message msg = Message.obtain();        msg.what = SEND_MESSAGE_CODE;        Bundle data = new Bundle();        data.putString("msg", "你好，服务端，我是客户端");        msg.setData(data);        msg.replyTo = clientMessenger;        try {            logger.debug(TAG_PROVIDER + "客户端向service发送信息");            serviceMessenger.send(msg);        } catch (RemoteException e) {            e.printStackTrace();            logger.debug(TAG_PROVIDER + "客户端向service发送消息失败: " + e.getMessage());        }    }    @Override    public void onServiceDisconnected(ComponentName name) {        serviceMessenger = null;        isBound = false;        logger.debug(TAG_PROVIDER + "客户端断开连接");    }};private void bindMessageService(Context context) {    Intent intent = new Intent();    intent.setAction(SERVICE_ACTION);    intent.addCategory(Intent.CATEGORY_DEFAULT);    PackageManager pm = context.getPackageManager();    ResolveInfo info = pm.resolveService(intent, 0);    if (info != null) {        String packageName = info.serviceInfo.packageName;        String serviceNmae = info.serviceInfo.name;        ComponentName componentName = new ComponentName(packageName, serviceNmae);        intent.setComponent(componentName);        try {            logger.debug(TAG_PROVIDER + "客户端调用bindService方法");            context.bindService(intent, conn, Context.BIND_AUTO_CREATE);        } catch (Exception e) {            e.printStackTrace();            logger.debug(TAG_PROVIDER + e.getMessage());        }    }}

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