Android Camera Client&Service 函数调用关系

1. JNI

@frameworks/base/core/jni/android_hardware_Camera.cpp

static void android_hardware_Camera_native_setup(JNIEnv *env, jobject thiz,
    jobject weak_this, jint cameraId)
{
    sp<Camera> camera = Camera::connect(cameraId);

    if (camera == NULL) {
        jniThrowRuntimeException(env, "Fail to connect to camera service");
        return;
    }

    // make sure camera hardware is alive
    if (camera->getStatus() != NO_ERROR) {
        jniThrowRuntimeException(env, "Camera initialization failed");
        return;
    }

    jclass clazz = env->GetObjectClass(thiz);
    if (clazz == NULL) {
        jniThrowRuntimeException(env, "Can't find android/hardware/Camera");
        return;
    }

    // We use a weak reference so the Camera object can be garbage collected.
    // The reference is only used as a proxy for callbacks.
    sp<JNICameraContext> context = new JNICameraContext(env, weak_this, clazz, camera);
    context->incStrong(thiz);
    camera->setListener(context);

    // save context in opaque field
    env->SetIntField(thiz, fields.context, (int)context.get());
}

 Class JNICameraContext 的定义：

// provides persistent context for calls from native code to Java
class JNICameraContext: public CameraListener
{
public:
    JNICameraContext(JNIEnv* env, jobject weak_this, jclass clazz, const sp<Camera>& camera);
    ~JNICameraContext() { release(); }
    virtual void notify(int32_t msgType, int32_t ext1, int32_t ext2);
    virtual void postData(int32_t msgType, const sp<IMemory>& dataPtr,
                          camera_frame_metadata_t *metadata);
    virtual void postDataTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr);
    void postMetadata(JNIEnv *env, int32_t msgType, camera_frame_metadata_t *metadata);
    void addCallbackBuffer(JNIEnv *env, jbyteArray cbb, int msgType);
    void setCallbackMode(JNIEnv *env, bool installed, bool manualMode);
    sp<Camera> getCamera() { Mutex::Autolock _l(mLock); return mCamera; }
    bool isRawImageCallbackBufferAvailable() const;
    void release();

private:
    void copyAndPost(JNIEnv* env, const sp<IMemory>& dataPtr, int msgType);
    void clearCallbackBuffers_l(JNIEnv *env, Vector<jbyteArray> *buffers);
    void clearCallbackBuffers_l(JNIEnv *env);
    jbyteArray getCallbackBuffer(JNIEnv *env, Vector<jbyteArray> *buffers, size_t bufferSize);

    jobject     mCameraJObjectWeak;     // weak reference to java object
    jclass      mCameraJClass;          // strong reference to java class
    sp<Camera>  mCamera;                // strong reference to native object
    jclass      mFaceClass;  // strong reference to Face class
    jclass      mRectClass;  // strong reference to Rect class
    Mutex       mLock;

    /*
     * Global reference application-managed raw image buffer queue.
     *
     * Manual-only mode is supported for raw image callbacks, which is
     * set whenever method addCallbackBuffer() with msgType =
     * CAMERA_MSG_RAW_IMAGE is called; otherwise, null is returned
     * with raw image callbacks.
     */
    Vector<jbyteArray> mRawImageCallbackBuffers;

    /*
     * Application-managed preview buffer queue and the flags
     * associated with the usage of the preview buffer callback.
     */
    Vector<jbyteArray> mCallbackBuffers; // Global reference application managed byte[]
    bool mManualBufferMode;              // Whether to use application managed buffers.
    bool mManualCameraCallbackSet;       // Whether the callback has been set, used to
                                         // reduce unnecessary calls to set the callback.
};

Class JNICameraContext继承了接口类CameraListener（@Camera.h），Class CameraListener定义如下：

// ref-counted object for callbacks
class CameraListener: virtual public RefBase
{
public:
    virtual void notify(int32_t msgType, int32_t ext1, int32_t ext2) = 0;
    virtual void postData(int32_t msgType, const sp<IMemory>& dataPtr,
                          camera_frame_metadata_t *metadata) = 0;
    virtual void postDataTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr) = 0;
};

Class CameraListener定义了三个纯虚函数，这三个纯虚函数都被Class JNICameraContext继承实现(@android_hardware_Camera.cpp)

void JNICameraContext::notify(int32_t msgType, int32_t ext1, int32_t ext2)
{
    ALOGV("notify");

    // VM pointer will be NULL if object is released
    Mutex::Autolock _l(mLock);
    if (mCameraJObjectWeak == NULL) {
        ALOGW("callback on dead camera object");
        return;
    }
    JNIEnv *env = AndroidRuntime::getJNIEnv();

    /*
     * If the notification or msgType is CAMERA_MSG_RAW_IMAGE_NOTIFY, change it
     * to CAMERA_MSG_RAW_IMAGE since CAMERA_MSG_RAW_IMAGE_NOTIFY is not exposed
     * to the Java app.
     */
    if (msgType == CAMERA_MSG_RAW_IMAGE_NOTIFY) {
        msgType = CAMERA_MSG_RAW_IMAGE;
    }

    env->CallStaticVoidMethod(mCameraJClass, fields.post_event,
            mCameraJObjectWeak, msgType, ext1, ext2, NULL);
}

void JNICameraContext::postData(int32_t msgType, const sp<IMemory>& dataPtr,
                                camera_frame_metadata_t *metadata)
{
    // VM pointer will be NULL if object is released
    Mutex::Autolock _l(mLock);
    JNIEnv *env = AndroidRuntime::getJNIEnv();
    if (mCameraJObjectWeak == NULL) {
        ALOGW("callback on dead camera object");
        return;
    }

    int32_t dataMsgType = msgType & ~CAMERA_MSG_PREVIEW_METADATA;

    // return data based on callback type
    switch (dataMsgType) {
        case CAMERA_MSG_VIDEO_FRAME:
            // should never happen
            break;

        // For backward-compatibility purpose, if there is no callback
        // buffer for raw image, the callback returns null.
        case CAMERA_MSG_RAW_IMAGE:
            ALOGV("rawCallback");
            if (mRawImageCallbackBuffers.isEmpty()) {
                env->CallStaticVoidMethod(mCameraJClass, fields.post_event,
                        mCameraJObjectWeak, dataMsgType, 0, 0, NULL);
            } else {
                copyAndPost(env, dataPtr, dataMsgType);
            }
            break;

        // There is no data.
        case 0:
            break;

        default:
            ALOGV("dataCallback(%d, %p)", dataMsgType, dataPtr.get());
            copyAndPost(env, dataPtr, dataMsgType);
            break;
    }

    // post frame metadata to Java
    if (metadata && (msgType & CAMERA_MSG_PREVIEW_METADATA)) {
        postMetadata(env, CAMERA_MSG_PREVIEW_METADATA, metadata);
    }
}

void JNICameraContext::postDataTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr)
{
    // TODO: plumb up to Java. For now, just drop the timestamp
    postData(msgType, dataPtr, NULL);
}

接下来看从JNI到Camera类的调用

camera->setListener(context);

 

2、Camera&BnCameraClient @frameworks/av/camera/Camera.cpp

void Camera::setListener(const sp<CameraListener>& listener)
{
    Mutex::Autolock _l(mLock);
    mListener = listener;
}

mListener定义在Class Camera中：

class Camera : public BnCameraClient, public IBinder::DeathRecipient
{
...
private: 
           sp<CameraListener>  mListener;
….
}

在Camera类中定义了三个回调函数，会用到mListener，

// callback from camera service
void Camera::notifyCallback(int32_t msgType, int32_t ext1, int32_t ext2)
{
    sp<CameraListener> listener;
    {
        Mutex::Autolock _l(mLock);
        listener = mListener;
    }
    if (listener != NULL) {
        listener->notify(msgType, ext1, ext2);
    }
}

// callback from camera service when frame or image is ready
void Camera::dataCallback(int32_t msgType, const sp<IMemory>& dataPtr,
                          camera_frame_metadata_t *metadata)
{
    sp<CameraListener> listener;
    {
        Mutex::Autolock _l(mLock);
        listener = mListener;
    }
    if (listener != NULL) {
        listener->postData(msgType, dataPtr, metadata);
    }
}

// callback from camera service when timestamped frame is ready
void Camera::dataCallbackTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr)
{
    // If recording proxy listener is registered, forward the frame and return.
    // The other listener (mListener) is ignored because the receiver needs to
    // call releaseRecordingFrame.
    sp<ICameraRecordingProxyListener> proxylistener;
    {
        Mutex::Autolock _l(mLock);
        proxylistener = mRecordingProxyListener;
    }
    if (proxylistener != NULL) {
        proxylistener->dataCallbackTimestamp(timestamp, msgType, dataPtr);
        return;
    }

    sp<CameraListener> listener;
    {
        Mutex::Autolock _l(mLock);
        listener = mListener;
    }
    if (listener != NULL) {
        listener->postDataTimestamp(timestamp, msgType, dataPtr);
    } else {
        ALOGW("No listener was set. Drop a recording frame.");
        releaseRecordingFrame(dataPtr);
    }
}

而三个函数是Camera类继承父类BnCameraClient的函数实现，而BnCameraClient继承接口类BnInterface<ICameraClient>

 

class Camera : public BnCameraClient, public Ibinder::DeathRecipient
{
...
}

class ICameraClient: public IInterface
{
public:
    DECLARE_META_INTERFACE(CameraClient);

    virtual void            notifyCallback(int32_t msgType, int32_t ext1, int32_t ext2) = 0;
    virtual void            dataCallback(int32_t msgType, const sp<IMemory>& data,
                                         camera_frame_metadata_t *metadata) = 0;
    virtual void            dataCallbackTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& data) = 0;
};

// ----------------------------------------------------------------------------

class BnCameraClient: public BnInterface<ICameraClient>
{
public:
    virtual status_t    onTransact( uint32_t code,
                                    const Parcel& data,
                                    Parcel* reply,
                                    uint32_t flags = 0);
};

看一下BnCameraClient::onTransact的实现：

status_t BnCameraClient::onTransact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
    switch(code) {
        case NOTIFY_CALLBACK: {
            ALOGV("NOTIFY_CALLBACK");
            CHECK_INTERFACE(ICameraClient, data, reply);
            int32_t msgType = data.readInt32();
            int32_t ext1 = data.readInt32();
            int32_t ext2 = data.readInt32();
            notifyCallback(msgType, ext1, ext2);
            return NO_ERROR;
        } break;
        case DATA_CALLBACK: {
            ALOGV("DATA_CALLBACK");
            CHECK_INTERFACE(ICameraClient, data, reply);
            int32_t msgType = data.readInt32();
            sp<IMemory> imageData = interface_cast<IMemory>(data.readStrongBinder());
            camera_frame_metadata_t *metadata = NULL;
            if (data.dataAvail() > 0) {
                metadata = new camera_frame_metadata_t;
                metadata->number_of_faces = data.readInt32();
                metadata->faces = (camera_face_t *) data.readInplace(
                        sizeof(camera_face_t) * metadata->number_of_faces);
            }
            dataCallback(msgType, imageData, metadata);
            if (metadata) delete metadata;
            return NO_ERROR;
        } break;
        case DATA_CALLBACK_TIMESTAMP: {
            ALOGV("DATA_CALLBACK_TIMESTAMP");
            CHECK_INTERFACE(ICameraClient, data, reply);
            nsecs_t timestamp = data.readInt64();
            int32_t msgType = data.readInt32();
            sp<IMemory> imageData = interface_cast<IMemory>(data.readStrongBinder());
            dataCallbackTimestamp(timestamp, msgType, imageData);
            return NO_ERROR;
        } break;
        default:
            return BBinder::onTransact(code, data, reply, flags);
    }
}

onTransact()函数实现了三种类型的回调。那是谁在调用这些毁掉函数？

3、CameraService&BpCameraClient

先不关心Binder的细节，找一下BpCameraClient类

@frameworks/av/camera/ICameraClient.cpp

class BpCameraClient: public BpInterface<ICameraClient>
{
public:
    BpCameraClient(const sp<IBinder>& impl)
        : BpInterface<ICameraClient>(impl)
    {
    }

    // generic callback from camera service to app
    void notifyCallback(int32_t msgType, int32_t ext1, int32_t ext2)
    {
        ALOGV("notifyCallback");
        Parcel data, reply;
        data.writeInterfaceToken(ICameraClient::getInterfaceDescriptor());
        data.writeInt32(msgType);
        data.writeInt32(ext1);
        data.writeInt32(ext2);
        remote()->transact(NOTIFY_CALLBACK, data, &reply, IBinder::FLAG_ONEWAY);
    }

    // generic data callback from camera service to app with image data
    void dataCallback(int32_t msgType, const sp<IMemory>& imageData,
                      camera_frame_metadata_t *metadata)
    {
        ALOGV("dataCallback");
        Parcel data, reply;
        data.writeInterfaceToken(ICameraClient::getInterfaceDescriptor());
        data.writeInt32(msgType);
        data.writeStrongBinder(imageData->asBinder());
        if (metadata) {
            data.writeInt32(metadata->number_of_faces);
            data.write(metadata->faces, sizeof(camera_face_t) * metadata->number_of_faces);
        }
        remote()->transact(DATA_CALLBACK, data, &reply, IBinder::FLAG_ONEWAY);
    }

    // generic data callback from camera service to app with image data
    void dataCallbackTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& imageData)
    {
        ALOGV("dataCallback");
        Parcel data, reply;
        data.writeInterfaceToken(ICameraClient::getInterfaceDescriptor());
        data.writeInt64(timestamp);
        data.writeInt32(msgType);
        data.writeStrongBinder(imageData->asBinder());
        remote()->transact(DATA_CALLBACK_TIMESTAMP, data, &reply, IBinder::FLAG_ONEWAY);
    }
};

这部分是在CameraService中被调用，那么，Camera的Client与service之间是如何建立联系的？

4、Camera<->CameraService

Camera app通过framework中的Camera Java类进入JNI部分，在android_hard_camera.cpp中:

android_hardware_Camera_native_setup()
{
    sp<Camera> camera = Camera::connect();
}

@Camera.cpp

sp<Camera> Camera::connect(int cameraId)
{
    ALOGV("connect");
    sp<Camera> c = new Camera();
    const sp<ICameraService>& cs = getCameraService();
    if (cs != 0) {
        c->mCamera = cs->connect(c, cameraId);
    }
    if (c->mCamera != 0) {
        c->mCamera->asBinder()->linkToDeath(c);
        c->mStatus = NO_ERROR;
    } else {
        c.clear();
    }
    return c;
}

这里首先New一个Camera对象，

getCameraService()会返回跨进程的ICameraService，

// establish binder interface to camera service
const sp<ICameraService>& Camera::getCameraService()
{
    Mutex::Autolock _l(mLock);
    if (mCameraService.get() == 0) {
        sp<IServiceManager> sm = defaultServiceManager();
        sp<IBinder> binder;
        do {
            binder = sm->getService(String16("media.camera"));
            if (binder != 0)
                break;
            ALOGW("CameraService not published, waiting...");
            usleep(500000); // 0.5 s
        } while(true);
        if (mDeathNotifier == NULL) {
            mDeathNotifier = new DeathNotifier();
        }
        binder->linkToDeath(mDeathNotifier);
        mCameraService = interface_cast<ICameraService>(binder);
    }
    ALOGE_IF(mCameraService==0, "no CameraService!?");
    return mCameraService;
}

Service的获取最后再讲;

最重要的，把返回的binder对象经过interface_cast<ICameraService>转换，变成了BpCameraService类型：

@IInterface

template<typename INTERFACE>
inline sp<INTERFACE> interface_cast(const sp<IBinder>& obj)
{
    return INTERFACE::asInterface(obj);
}

sp<I##INTERFACE> I##INTERFACE::asInterface(const sp<IBinder>& obj) 
{ 
    sp<I##INTERFACE> intr; 
    if (obj != NULL) { 
        intr = static_cast<I##INTERFACE*>( 
            obj->queryLocalInterface( 
                I##INTERFACE::descriptor).get()); 
        if (intr == NULL) { 
            intr = new Bp##INTERFACE(obj); 
        } 
    } 
    return intr; 
} 

然后在其上调用connect（ICameraService::connect）:

class BpCameraService: public BpInterface<ICameraService>
{
public:
    BpCameraService(const sp<IBinder>& impl)
        : BpInterface<ICameraService>(impl)
    {
    }

    // get number of cameras available
    virtual int32_t getNumberOfCameras()
    {
        Parcel data, reply;
        data.writeInterfaceToken(ICameraService::getInterfaceDescriptor());
        remote()->transact(BnCameraService::GET_NUMBER_OF_CAMERAS, data, &reply);
        return reply.readInt32();
    }

    // get information about a camera
    virtual status_t getCameraInfo(int cameraId,
                                   struct CameraInfo* cameraInfo) {
        Parcel data, reply;
        data.writeInterfaceToken(ICameraService::getInterfaceDescriptor());
        data.writeInt32(cameraId);
        remote()->transact(BnCameraService::GET_CAMERA_INFO, data, &reply);
        cameraInfo->facing = reply.readInt32();
        cameraInfo->orientation = reply.readInt32();
        return reply.readInt32();
    }

    // connect to camera service
    virtual sp<ICamera> connect(const sp<ICameraClient>& cameraClient, int cameraId)
    {
        Parcel data, reply;
        data.writeInterfaceToken(ICameraService::getInterfaceDescriptor());
        data.writeStrongBinder(cameraClient->asBinder());
        data.writeInt32(cameraId);
        remote()->transact(BnCameraService::CONNECT, data, &reply);
        return interface_cast<ICamera>(reply.readStrongBinder());
    }
};

这里会向remote发起一个transaction，然后在reply中读取binder，经过interface_cast<ICamera>转换为BpCamera类型。BpCamera是一个非常重要的类型，所有的Camera功能性的调用都是由他过度。

那么BnCameraService::CONNECT的实现是怎样的呢？注意此transaction的参数中有一个是const sp<ICameraClient>& cameraClient，

BnCameraService::onTransact()
status_t BnCameraService::onTransact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
    switch(code) {
        case GET_NUMBER_OF_CAMERAS: {
           …
          } break;
        case GET_CAMERA_INFO: {
        …
       } break;
        case CONNECT: {
            CHECK_INTERFACE(ICameraService, data, reply);
            sp<ICameraClient> cameraClient = interface_cast<ICameraClient>(data.readStrongBinder());
            sp<ICamera> camera = connect(cameraClient, data.readInt32());
            reply->writeStrongBinder(camera->asBinder());
            return NO_ERROR;
        } break;
        default:
            return BBinder::onTransact(code, data, reply, flags);
    }
}

这里从data中得到ICameraClient类型，之后以此为参数调用connect(), connect在BnCameraService中没有实现，调用子类Class CameraService 的connect:

class CameraService :
    public BinderService<CameraService>,
    public BnCameraService
{   
    virtual sp<ICamera> connect(const sp<ICameraClient>& cameraClient, int cameraId);
 }

sp<ICamera> CameraService::connect(const sp<ICameraClient>& cameraClient)
{
        ...
    client = new Client(this, cameraClient, callingPid);
    return client;
        ...  
}

在new client时将 cameraClient传入：

CameraService::Client::Client(const sp<CameraService>& cameraService,
        const sp<ICameraClient>& cameraClient,
        const sp<CameraHardwareInterface>& hardware,
        int cameraId, int cameraFacing, int clientPid) {
    int callingPid = getCallingPid();
    LOG1("Client::Client E (pid %d, id %d)", callingPid, cameraId);

    mCameraService = cameraService;
    mCameraClient = cameraClient;
...
 }

之后，CameraService就可以通过mCameraClient对象来调用Cameraclient端的回调函数，在类CameraService的Client类中定义一些回调函数都由此实现：

  class Client : public BnCamera
    {
        // these are static callback functions
        static void             notifyCallback(int32_t msgType, int32_t ext1, int32_t ext2, void* user);
        static void             dataCallback(int32_t msgType, const sp<IMemory>& dataPtr,
                                             camera_frame_metadata_t *metadata, void* user);
        static void             dataCallbackTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr, void* user);
        static Mutex*        getClientLockFromCookie(void* user);
        // convert client from cookie. Client lock should be acquired before getting Client.
        static Client*       getClientFromCookie(void* user);
        // handlers for messages
        void                    handleShutter(void);
        void                    handlePreviewData(int32_t msgType, const sp<IMemory>& mem,
                                                  camera_frame_metadata_t *metadata);
        void                    handlePostview(const sp<IMemory>& mem);
        void                    handleRawPicture(const sp<IMemory>& mem);
        void                    handleCompressedPicture(const sp<IMemory>& mem);
        void                    handleGenericNotify(int32_t msgType, int32_t ext1, int32_t ext2);
        void                    handleGenericData(int32_t msgType, const sp<IMemory>& dataPtr,
                                                  camera_frame_metadata_t *metadata);
        void                    handleGenericDataTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr);

        void                    copyFrameAndPostCopiedFrame(
                                    int32_t msgType,
                                    const sp<ICameraClient>& client,
                                    const sp<IMemoryHeap>& heap,
                                    size_t offset, size_t size,
                                    camera_frame_metadata_t *metadata);
}

由此可以实现从service到client的调用

另外注意CameraService::connect的返回值

sp<ICamera> CameraService::connect(const sp<ICameraClient>& cameraClient)
{
    client = new Client(this, cameraClient, callingPid);
    return client;
}

client 经transaction 的reply返回，而被Client端获取，Client端可由此发起从Client向service的调用。

5、除了Class Camera及Class ICameraClient，还有一个稍不重要的类Class ICameraService。用于建立Camera及ICameraClient。用法与上面的connect()函数类似，

其主要目的是为了通过CameraService获取Camera相关信息，用于建立Client及ICameraClient

@ICameraService

class BpCameraService: public BpInterface<ICameraService>
{
public:
    BpCameraService(const sp<IBinder>& impl)
        : BpInterface<ICameraService>(impl)
    {
    }

    // get number of cameras available
    virtual int32_t getNumberOfCameras()
    {
        Parcel data, reply;
        data.writeInterfaceToken(ICameraService::getInterfaceDescriptor());
        remote()->transact(BnCameraService::GET_NUMBER_OF_CAMERAS, data, &reply);
        return reply.readInt32();
    }

    // get information about a camera
    virtual status_t getCameraInfo(int cameraId,
                                   struct CameraInfo* cameraInfo) {
        Parcel data, reply;
        data.writeInterfaceToken(ICameraService::getInterfaceDescriptor());
        data.writeInt32(cameraId);
        remote()->transact(BnCameraService::GET_CAMERA_INFO, data, &reply);
        cameraInfo->facing = reply.readInt32();
        cameraInfo->orientation = reply.readInt32();
        return reply.readInt32();
    }

    // connect to camera service
    virtual sp<ICamera> connect(const sp<ICameraClient>& cameraClient, int cameraId)
    {
        Parcel data, reply;
        data.writeInterfaceToken(ICameraService::getInterfaceDescriptor());
        data.writeStrongBinder(cameraClient->asBinder());
        data.writeInt32(cameraId);
        remote()->transact(BnCameraService::CONNECT, data, &reply);
        return interface_cast<ICamera>(reply.readStrongBinder());
    }
}

status_t BnCameraService::onTransact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
    switch(code) {
        case GET_NUMBER_OF_CAMERAS: {
            CHECK_INTERFACE(ICameraService, data, reply);
            reply->writeInt32(getNumberOfCameras());
            return NO_ERROR;
        } break;
        case GET_CAMERA_INFO: {
            CHECK_INTERFACE(ICameraService, data, reply);
            CameraInfo cameraInfo;
            memset(&cameraInfo, 0, sizeof(cameraInfo));
            status_t result = getCameraInfo(data.readInt32(), &cameraInfo);
            reply->writeInt32(cameraInfo.facing);
            reply->writeInt32(cameraInfo.orientation);
            reply->writeInt32(result);
            return NO_ERROR;
        } break;
        case CONNECT: {
            CHECK_INTERFACE(ICameraService, data, reply);
            sp<ICameraClient> cameraClient = interface_cast<ICameraClient>(data.readStrongBinder());
            sp<ICamera> camera = connect(cameraClient, data.readInt32());
            reply->writeStrongBinder(camera->asBinder());
            return NO_ERROR;
        } break;
        default:
            return BBinder::onTransact(code, data, reply, flags);
    }
}