Android Service Messenger & AIDL 的跨進程通信例子

很久沒用跨進程通信了，然後等自己又要用的時候，網上一搜，千遍一律，還很渣，吐血~

工程有兩份`MessengerService`&`MessengerActivity`，前個提供服務，後個訪問服務。

跨進程通信

就多個apk互相通信，當然廣播也是不錯的。不過這裏用的是Messenger和AIDL，並且都弄成雙向的了。

Messenger

信使，底層說是也用的AIDL。用起來挺方便的。

MessengerService

1）AndroidManifest.xml聲明權限

<permission
    android:name="org.join.permission.SERVICE"
    android:protectionLevel="normal" >
</permission>

<uses-permission android:name="org.join.permission.SERVICE" />

爲什麼弄個帶權限的呢？因爲討厭任何警告==。

2）註冊MessengerService

<service
    android:name="org.join.messenger.MessengerService"
    android:exported="true"
    android:permission="org.join.permission.SERVICE"
    android:process=":remote" >
    <intent-filter>
        <action android:name="org.join.service.MESSENGER" />
    </intent-filter>
</service>

這裏把權限加上了，不然最新ADT是會有個警告的。就一嘀咕的老頭，討人厭。

3）MessengerService核心代碼

public class MessengerService extends Service implements MessageCode {

    static final String TAG = "MessengerService";

    public static final String ACTION = "org.join.service.MESSENGER";

    // 第一步：新建
    final Messenger mMessenger = new Messenger(new Handler() {

        // 第二步：處理Message
        @Override
        public void dispatchMessage(Message msg) {
            switch (msg.what) {
            case CLNT_REQ_HELLO:
                toast("Hello!");
                Bundle data = new Bundle();
                data.putString("msg", "Who am I?");
                // 這個`msg.replyTo`是客戶端的信使
                respClnt(msg.replyTo, SERV_RES_HAHA, data);
                break;
            case CLNT_REQ_SURPRISE:
                String s = msg.getData().getString("msg");
                toast("Surprise! " + s);
                break;
            }
        }

        // 第三步：回覆用，注意`msg.replyTo`。
        private void respClnt(Messenger clnt, int msgCode, Bundle data) {
            if (clnt == null) {
                return;
            }
            try {
                Message msg = Message.obtain(null, msgCode);
                msg.replyTo = mMessenger; // 綁定服務端信使
                if (data != null) {
                    msg.setData(data);
                }
                clnt.send(msg); // 用客戶端信使發消息
            } catch (RemoteException e) {
                e.printStackTrace();
            }
        }
    });

    @Override
    public IBinder onBind(Intent intent) {
        Log.e(TAG, "onBind");
        return mMessenger.getBinder();
    }

    // ......

}

MessengerActivity

1）AndroidManifest.xml聲明權限

<uses-permission android:name="org.join.permission.SERVICE" />

2）MessengerActivity核心代碼

1. 創建Messenger

// 服務端的信使，後面會綁定
private Messenger mService;

// 第一步：新建
final Messenger mMessenger = new Messenger(new Handler() {

    // 第二步：處理Message
    @Override
    public void dispatchMessage(Message msg) {
        switch (msg.what) {
        case SERV_RES_HAHA:
            String s = msg.getData().getString("msg");
            toast("HAHA! " + s);
            Bundle data = new Bundle();
            data.putString("msg", "I am you.");
            sendMsg(CLNT_REQ_SURPRISE, data);
            break;
        }
    }
});

// 第三步：回覆用，同樣注意`msg.replyTo`。
private void sendMsg(int msgCode, Bundle data) {
    if (mService == null) {
        toast("Service is disconnected!");
        return;
    }
    try {
        Message msg = Message.obtain(null, msgCode);
        msg.replyTo = mMessenger; // 綁定客戶端信使
        if (data != null) {
            msg.setData(data);
        }
        mService.send(msg); // 用服務端信使發消息
    } catch (RemoteException e) {
        e.printStackTrace();
    }
}

2. 綁定Service

// 和一般綁定Service一樣
private ServiceConnection servConnection = new ServiceConnection() {

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        mService = new Messenger(service); // 不過，這裏改爲Messenger
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        mService = null;
    }
};

// 綁定方法
protected void doBindService() {
    bindService(new Intent("org.join.service.MESSENGER"), servConnection, BIND_AUTO_CREATE);
    isBound = true;
}

// 解綁方法
protected void doUnbindService() {
    if (isBound) {
        unbindService(servConnection);
        isBound = false;
    }
}

好了，客戶端要發送消息，調用sendMsg()就可以了。

AIDL

也挺簡單的，恩，繼續...

RemoteService

1）AndroidManifest.xml聲明權限，就之前的，ok了。

2）註冊RemoteService

<service
    android:name="org.join.aidl.RemoteService"
    android:exported="true"
    android:permission="org.join.permission.SERVICE"
    android:process=":remote" >
    <intent-filter>
        <action android:name="org.join.service.AIDL" />
    </intent-filter>
</service>

3）搞個parcelable對象

不能就用基本類型是不，所以要搞個對象^^。

恩，Event.java就是了。然後要爲它寫個aidl。

Event.aidl

package org.join.aidl;

parcelable Event;

簡單吧。

4）然後弄個Callback

不能就單向通信是不，所以要用來回調客戶端。

IRemoteCallback.aidl

package org.join.aidl;

import org.join.aidl.Event;

/**
 * @brief 遠程回調
 * @author join
 */
interface IRemoteCallback {

    void onEvent(in Event event);

}

4）服務的AIDL了

IRemoteService.aidl

package org.join.aidl;

import org.join.aidl.IRemoteCallback;
import org.join.aidl.Event;

/**
 * @brief 遠程服務
 * @author join
 */
interface IRemoteService {

    void registerCallback(in IRemoteCallback cb);

    void unregisterCallback(in IRemoteCallback cb);

    Event requestEvent();

}

5）哦，總算到RemoteService了

RemoteService.java，恩，直接參考了ApiDemo，捂臉~

public class RemoteService extends Service {

    static final String TAG = "RemoteService";

    public static final String ACTION = "org.join.service.AIDL";

    final RemoteCallbackList<IRemoteCallback> mCallbacks = new RemoteCallbackList<IRemoteCallback>();

    private final IRemoteService.Stub mBinder = new IRemoteService.Stub() {

        @Override
        public void registerCallback(IRemoteCallback cb) throws RemoteException {
            if (cb != null)
                mCallbacks.register(cb);
        }

        @Override
        public void unregisterCallback(IRemoteCallback cb) throws RemoteException {
            if (cb != null)
                mCallbacks.unregister(cb);
        }

        @Override
        public Event requestEvent() throws RemoteException {
            Event event = new Event();
            event.setId(Integer.MAX_VALUE);
            event.setName("Are you?");
            return event;
        }
    };

    private static final int REPORT_EVENT = 1;

    private final Handler mHandler = new Handler() {

        private Event event = new Event();
        private int count = 0;

        @Override
        public void dispatchMessage(Message msg) {
            switch (msg.what) {
            case REPORT_EVENT: {
                event.setId(count);
                event.setName("name" + count);
                count++;

                // Broadcast to all clients the new value.
                final int N = mCallbacks.beginBroadcast();
                for (int i = 0; i < N; i++) {
                    try {
                        mCallbacks.getBroadcastItem(i).onEvent(event);
                    } catch (RemoteException e) {
                        // The RemoteCallbackList will take care of removing the dead object for us.
                    }
                }
                mCallbacks.finishBroadcast();

                // Repeat every 1 second.
                sendMessageDelayed(obtainMessage(REPORT_EVENT), 1 * 1000);
            }
                break;
            default:
                super.handleMessage(msg);
            }
        }
    };

    @Override
    public IBinder onBind(Intent intent) {
        Log.e(TAG, "onBind");
        return mBinder;
    }

    @Override
    public void onCreate() {
        Log.e(TAG, "onCreate");
        super.onCreate();
        mHandler.sendEmptyMessage(REPORT_EVENT);
    }

    @Override
    public void onDestroy() {
        Log.e(TAG, "onDestroy");
        super.onDestroy();
        mHandler.removeMessages(REPORT_EVENT);
    }

    // ......

}

只要這個服務開啓，每1秒回調下onEvent()。

至於RemoteCallbackList，是方便我們管理的，不然在RemoteException時，我們要親自remote才行。

MessengerActivity

1）AndroidManifest.xml聲明權限，也是之前的，ok了。

2）然後，之前辛苦工作的獎勵時間^^

把Event.java、Event.aidl、IRemoteCallback.aidl、IRemoteService.aidl拷貝過來，開心吧。

3）還是MessengerActivity內綁定

1. 回調和請求

// 遠程服務，後面會綁定
private IRemoteService mRemoteService = null;

// 回調的實現，注意了吧，要用handler，之前也是。
private IRemoteCallback mCallback = new IRemoteCallback.Stub() {
    @Override
    public void onEvent(Event event) throws RemoteException {
        mHandler.sendMessage(mHandler.obtainMessage(BUMP_EVENT, event));
    }
};

private static final int BUMP_EVENT = 1;

private Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
        case BUMP_EVENT:
            Event event = (Event) msg.obj;
            tvEvent.setText(event.toString());
            break;
        default:
            super.handleMessage(msg);
        }
    }

};

// 直接請求事件
public void reqEvent(View v) {
    Event event = null;
    try {
        if (mRemoteService != null) {
            event = mRemoteService.requestEvent();
        }
    } catch (RemoteException e) {
    } finally {
        toast(event == null ? "Remote service is disconnected!" : event.toString());
    }
}

2. 綁定Service

// 同樣是綁定Service的過程
private ServiceConnection servRemoteConnection = new ServiceConnection() {
    public void onServiceConnected(ComponentName className, IBinder service) {
        mRemoteService = IRemoteService.Stub.asInterface(service); // 這裏，綁定的遠程服務
        tvEvent.setText("Attached.");
        try {
            mRemoteService.registerCallback(mCallback); // 調用服務方法註冊回調
        } catch (RemoteException e) {
        }
    }

    public void onServiceDisconnected(ComponentName className) {
        mRemoteService = null;
        btnServAidl.setChecked(false);
        tvEvent.setText("Disconnected.");
    }
};

protected void doBindRemoteService() {
    bindService(new Intent("org.join.service.AIDL"), servRemoteConnection, BIND_AUTO_CREATE);
    isRemoteBound = true;
    tvEvent.setText("Binding.");
}

protected void doUnbindRemoteService() {
    if (isRemoteBound) {
        unbindService(servRemoteConnection);
        isRemoteBound = false;
    }
}

哦也，all done。

禮物

附贈兩個小工程

`AndroidFragment`

• Fragment組件的例子。
• 主要註釋，一些方法說明&注意點。

`AndroidJUnit`

• Run as -> Android JUnit test。
• 主要代碼，src/test目錄下。