BroadcastReceiver的思考（6）

上篇文章中我们谈到了，Service的远程沟通，既当Activity和Service不在一个进程中，它们之间是怎么相互通信的，不过只是停留在原理层面，今天傻蛋写了一个测试程序来进一步说明远程沟通机制。

Android框架的IPC沟通其实是依赖单一的IBinder接口，当Activity端呼叫IBinder接口的transact()函数时，就会透过IPC机制来呼叫远端的onTransact()函数。当调用transact函数之后，Android框架会根据线程的同步机制，等待远端的onTransact()函数执行完毕 并且返回，才继续向下面继续执行。傻蛋画了副图来进一步说明这个过程。

1. JavaBBinder是Android系统底层提供的类，其实它是个代理（代理模式），同时实现了IBinder接口，这样它onTransact()函数就能够调用myBinder的onTransact()函数
2. 当RemoteServiceTransactActivity需要夸进程来执行JavaBBinder的对象时，Android框架从RemoteServiceTransact所在的进程中启动一个线程Thread X来配合Thread A的执行，这样就变成进程内的通信了。
3. 通过这种远程代理的方式，使用者就会感觉到好像是在本地线程中执行程序一样了。

 

运行结果如下：

 

 

从结果我们可以看出Activity运行的线程名是main，Service运行的线程名也是main，不过和前面Activity的那个main不是一个，为了证明这一点我把它改名为main-changed，Binder所运行的线程名为Binder Thread #2 ，用来配合Activity主线程的远程调用。

测试代码如下：

^?[Copy to clipboard] Download RemoteMusicService.java

 

 

/**
 * RemoteMusicService.java
 * com.androidtest.service.mediaplayer
 *
 * Function： TODO
 *
 *   ver     date           author
 * ──────────────────────────────────
 *           2011-5-19      Leon
 *
 * Copyright (c) 2011, TNT All Rights Reserved.
*/

package com.androidtest.service;

import com.androidtest.R;
import com.androidtest.parcelable.ParcelableObject;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Binder;
import android.os.IBinder;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.RemoteException;
import android.util.Log;

/**
 * ClassName:RemoteMusicService
 * Function: TODO ADD FUNCTION
 * Reason:   TODO ADD REASON
 *
 * @author   Leon
 * @version
 * @since    Ver 1.1
 * @Date     2011-5-19
 */
public class RemoteServiceTransact extends Service {

    private IBinder mBinder = null ;
    private String  replyString;

    @Override
    public void onCreate() {

        // TODO Auto-generated method stub
        super.onCreate();
        mBinder = new myBinder();
        Thread.currentThread().setName("Service Thread Name : " +
                Thread.currentThread().getName()+"-chenaged");

    }

    @Override
    public IBinder onBind(Intent intent) {

        // TODO Auto-generated method stub
        replyString = Thread.currentThread().getName();
        return mBinder;

    }

    public  class myBinder extends Binder{

        @Override
        protected boolean onTransact(int code, Parcel data, Parcel reply,
                int flags) throws RemoteException {

            // TODO Auto-generated method stub
            reply.writeString(replyString +  " Binder Thread is :" + Thread.currentThread().getName());
            return true;

        }

    }

}

^?[Copy to clipboard] Download RemoteServiceTransactActivity.java

 

 

/**
 * RemoteServiceTransactActivity.java
 * com.androidtest.service
 *
 * Function： TODO
 *
 *   ver     date           author
 * ──────────────────────────────────
 *           2011-6-21      Leon
 *
 * Copyright (c) 2011, TNT All Rights Reserved.
*/

package com.androidtest.service;

import com.androidtest.service.mediaplayer.IMusicService;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.os.Parcel;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;

/**
 * ClassName:RemoteServiceTransactActivity
 * Function: TODO ADD FUNCTION
 * Reason:   TODO ADD REASON
 *
 * @author   Leon
 * @version
 * @since    Ver 1.1
 * @Date     2011-6-21
 */
public class RemoteServiceTransactActivity extends Activity {
    private static final String TAG= RemoteServiceTransactActivity.class.getSimpleName();
    private final int WC=LinearLayout.LayoutParams.WRAP_CONTENT;
    private final int WP=LinearLayout.LayoutParams.FILL_PARENT;
    private Button  buttonRunService ;
    private TextView textView ;
    private IBinder iBinder;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        LinearLayout  layout=new LinearLayout(this);
        layout.setOrientation(LinearLayout.VERTICAL);
        this.setTitle("Test Run  Service..");

        //定义Button
        buttonRunService=new Button(this);
        buttonRunService.setId(1);
        buttonRunService.setText("Run Service");
        buttonRunService.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                // TODO Auto-generated method stub
                Parcel sendParcel = Parcel.obtain();
                Parcel replyParcel =Parcel.obtain();
                try{
                    iBinder.transact(2, sendParcel, replyParcel, 0);
                    //先打印出Activity的主线程名 然后Service的主线程名更名然后返回，说明Service运行在不同
                                //的进程中
                    textView.setText("Activity Thread Name is :" +Thread.currentThread().getName()
                            +" and "+replyParcel.readString());
                }catch(Exception e){
                    e.printStackTrace();
                }

            }
        });
        //定义TextView
        textView = new TextView(this);
        textView.setText("Ready....");
        //加入到Layout中
        layout.addView(buttonRunService);
        layout.addView(textView);
        this.setContentView(layout);

        this.bindService(new Intent("com.androidtest.service.RemoteServiceTransact")
                   , myServiceConnection, Context.BIND_AUTO_CREATE);

    }

    private ServiceConnection myServiceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName name, IBinder binder) {
            iBinder=binder;
            Log.d(TAG, " onServiceConnected");
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

            Log.d(TAG, " onServiceDisconnected");
        }

    };

}

同时在Android Manifest中需要这样来定义这个Service,以便它能够在不同的进程中运行。

 

<service android:enabled="true" android:process=":remote"
                                        android:name=".service.RemoteServiceTransact">
     <intent-filter>
        <action android:name="com.androidtest.service.RemoteServiceTransact" />
     intent-filter>
 service>