一．服务端程序

1. 新建aidl文件，如ICameraCallback.aidl，添加客户端要回调的接口，例如：

package com.android.camera;
interface ICameraCallback {
		void onResult(String msg);
}

2. 新建一个单例的类, 如CameraControler.java, 实现进程内通信相关的接口,内容如下:

package com.android.camera;

public class CameraControler {
	private OnControlListener mListener = null;
	private static CameraControler sInstance = null;

	public static interface OnControlListener {
		void registerCallback(ICameraCallback cb);
		void unregisterCallback(ICameraCallback cb);
	}

	private CameraControler() {
	}

	public final static CameraControler getInstance() {
		if (sInstance == null) {
			synchronized (CameraControler.class) {
				if (sInstance == null) {
					CameraControler.sInstance = new CameraControler();
				}
			}
		}
		return sInstance;
	}

	public CameraControler setOnControlListener(OnControlListener listener) {
		mListener = listener;
		return this;
	}
	
	public void registerCallback(ICameraCallback cb) {
		if(mListener==null)
			return;
		mListener.registerCallback(cb);
	}
	
	public void unregisterCallback(ICameraCallback cb) {
		if(mListener==null)
			return;
		mListener.unregisterCallback(cb);
	}
}

3. 在要回调的类中实现注册回调和释放回调的接口，并在要回调的地方调用回调，例如：

private RemoteCallbackList<ICameraCallback> mCallbacks = new RemoteCallbackList<ICameraCallback>();
private CameraControler mCameraControler = CameraControler.getInstance();

mCameraControler.setOnControlListener(new CameraControler.OnControlListener() {
	@Override
	public void registerCallback(ICameraCallback cb) {
		if(mCallbacks!=null) mCallbacks.register(cb);
	}

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


public void onResult(String msg) {
    if(mCallbacks!=null) {
        int n = mCallbacks.beginBroadcast();
        try {
	    for(int i=0;i<n;i++) {
	        mCallbacks.getBroadcastItem(i).onRtmpConnected(msg);
	    }
        }catch(Exception e) {
            e.printStackTrace();
        }
        mCallbacks.finishBroadcast();
    }
}

4. 写一个服务,如CameraServer.java,声明单例对象,通过调用单例对象的对应接口注册和释放回调

package com.android.camera;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.RemoteException;

public class CameraServer extends Service {
	protected CameraControler mCameraControler = CameraControler.getInstance();
	@Override
	public IBinder onBind(Intent intent) {
		return new ICameraServer.Stub() {		
			@Override
			public void registerCallback(ICameraCallback cb) throws RemoteException {
				mCameraControler.registerCallback(cb);
			}

			@Override
			public void unregisterCallback(ICameraCallback cb) throws RemoteException {
				mCameraControler.unregisterCallback(cb);
			}
		};
	}
}

5. 在AndroidManifest.xml中添加服务的声明

        <service
            android:name="com.android.camera.CameraServer"
            android:enabled="true"
            android:label="@string/app_name" >  
            <intent-filter>
                <intent-filter>  
                	<action android:name="com.android.camera.ICameraServer" />
                	<category android:name="android.intent.category.DEFAULT" />
            	</intent-filter>
            </intent-filter>
        </service>

6. 新建aidl文件,如ICameraServer.aidl,其中添加注册和释放回调的接口，导入回调接口时要import全名(不能只import包名)如下:

package com.android.camera;
import com.android.camera.ICameraCallback;

interface ICameraServer {
	void registerCallback(ICameraCallback cb);
        void unregisterCallback(ICameraCallback cb);
}

7. 如果要放到系统源码中编码, 需要在Android.mk中添加引用,如下:

LOCAL_SRC_FILES += src/com/android/camera/ICameraServer.aidl
LOCAL_SRC_FILES += src/com/android/camera/ICameraCallback.aidl

二. 客户端程序

1. 把aidl文件拷贝到客户端程序中, 注意: aidl文件包名要与服务器包名一致; 并在要调用aidl接口的文件中声明ICameraServer camera;

2. 创建ServiceConnection对象，并在onServiceConnected中注册回调，如下:

private ServiceConnection CameraConnection = new ServiceConnection() {
	@Override
	public void onServiceConnected(ComponentName name, IBinder service) {
		camera = ICameraServer.Stub.asInterface(service);
		try {
			camera.registerCallback(mCameraCallback);
		} catch (RemoteException e) {
			e.printStackTrace();
		}
	}
	
	@Override
	public void onServiceDisconnected(ComponentName name) {
	}
};

3. 初始化时调用如下代码:

Intent intent = new Intent();
intent.setClassName("com.android.gallery3d", "com.android.camera.CameraServer");
bindService(intent, CameraConnection, Context.BIND_AUTO_CREATE);

4. Destroy时注销回调并解绑服务:

if(camera!=null) {
	try {
		camera.unregisterCallback(mCameraCallback);
	} catch (RemoteException e) {
		e.printStackTrace();
	}
}
unbindService(CameraConnection);
CameraConnection = null;