Android 使用Messenger跨進程通信（二）

Messenger：中文爲信使，他可以在不同進程中傳遞的Message對象，只需要在Message中放入我們所傳遞的信息（數據）即可。Messenger的使用流程可見下圖：

1.創建服務端Service來處理Client的連接請求，同事創建一個Handler，通過他創建Messenger對象，然後在onBinder()方法中返回，具體操作如下：

import android.app.Service;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.util.Log;

public class MsgService extends Service {
   
    public static final String TAG="MsgService";
    
    private static class MessengerHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 0:
                    Log.i(TAG,"收到客戶端發過來的消息:"+msg.getData().getString("msg"));
                    break;
                    default:
            }
            super.handleMessage(msg);
        }
    }
    private final Messenger mMessenger=new Messenger(new MessengerHandler());
    @Override
    public IBinder onBind(Intent intent) {
      return  mMessenger.getBinder();
    }
}

當然還有一步就是在清單文件註冊Service,如下：

 <service
            android:name=".MsgService"
            android:process=":remote"/>

然後，就是Client端發送信息，首先客服端要綁定Service，其次綁定成功後，根據服務端返回的Binder對象創建Messenger對象並使用此對象發送消息，具體如下：

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MsgActivity extends AppCompatActivity {

    private Messenger mServcie;
    
    private ServiceConnection mConnect=new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mServcie=new Messenger(service);
            Message msg=Message.obtain(null,0);
            Bundle bundle=new Bundle();
            bundle.putString("msg","你好，這裏客戶中心，你那邊是服務中心嗎？");
            msg.setData(bundle);
            try {
                mServcie.send(msg);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent intent=new Intent(this,MsgService.class);
        bindService(intent,mConnect,Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        unbindService(mConnect);
        super.onDestroy();
    }
}

上面演示了客戶端向服務端的信息傳遞，然而客戶端發送信息後，服務端沒有返回任何信息，下面做下小小改動讓服務端接收到客戶端的信息後，做出反應。

package com.example.app2;

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 android.util.Log;

public class MsgService extends Service {

    public static final String TAG="MsgService";

    private static class MessengerHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 0:
                    Log.i(TAG,"收到客戶端發過來的消息:"+msg.getData().getString("msg"));
                    Messenger messenger=msg.replyTo;
                    Message msgReply=Message.obtain(null,1);
                    Bundle bundle=new Bundle();
                    bundle.putString("reply","嗯，你好，這裏是服務中心，請說");
                    msgReply.setData(bundle);
                    try {
                        messenger.send(msgReply);
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                    break;
                    default:
            }
            super.handleMessage(msg);
        }
    }
    private final Messenger mMessenger=new Messenger(new MessengerHandler());
    @Override
    public IBinder onBind(Intent intent) {
      return  mMessenger.getBinder();
    }
}

爲了接收客戶端的修改，客戶端需要創建一個接受服務端消息的Messenger和Handler，具體如下：

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.Messenger;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

public class MsgActivity extends AppCompatActivity {

    private Messenger mServcie;

    /**
     * 用於處理服務端迴應的消息
     */
    private static class MessengerHandler extends Handler{
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 1:
                    Log.i("MsgActivity","來自服務端的迴應："+msg.getData().getString("reply"));
                    break;
                    default:
            }
            super.handleMessage(msg);
        }
    }
    private Messenger mReplyMessenger=new Messenger(new MessengerHandler());
    
    private ServiceConnection mConnect=new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mServcie=new Messenger(service);
            Message msg=Message.obtain(null,0);
            Bundle bundle=new Bundle();
            bundle.putString("msg","你好，這裏客戶中心，你那邊是服務中心嗎？");
            msg.setData(bundle);
            //接收服務端消息必須加這一句
            msg.replyTo=mReplyMessenger;
            try {
                mServcie.send(msg);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent intent=new Intent(this,MsgService.class);
        bindService(intent,mConnect,Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        unbindService(mConnect);
        super.onDestroy();
    }
}

參考資料：

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