- CameraBase基类介绍
这个类的定义如下：
template <typename TCam, typename TCamTraits = CameraTraits<TCam> >
class CameraBase : public IBinder::DeathRecipient
{
public:
??? typedef typename TCamTraits::TCamListener?????? TCamListener;
??? typedef typename TCamTraits::TCamUser?????????? TCamUser;
??? typedef typename TCamTraits::TCamCallbacks????? TCamCallbacks;
??? typedef typename TCamTraits::TCamConnectService TCamConnectService;
??? static sp<TCam>????? connect(int cameraId,
???????????????????????????????? const String16& clientPackageName,
???????????????????????????????? int clientUid, int clientPid);
??? virtual void???????? disconnect();
??? void???????????????? setListener(const sp<TCamListener>& listener);
??? static int?????????? getNumberOfCameras();
??? static status_t????? getCameraInfo(int cameraId,
?????????????????????????????????????? /*out*/
??????????????????????????????? ???????struct hardware::CameraInfo* cameraInfo);
??? sp<TCamUser>???????? remote();
??? // Status is set to 'UNKNOWN_ERROR' after successful (re)connection
??? status_t???????????? getStatus();
protected:
??? CameraBase(int cameraId);
??? virtual?????? ???????~CameraBase();
???
??? // TCamCallbacks implementation
???
??? virtual void???????? notifyCallback(int32_t msgType, int32_t ext,
???? ???????????????????????????????????int32_t ext2);
???
??? // Common instance variables
???
??? Mutex??????????????????????????? mLock;
??? virtual void???????????????????? binderDied(const wp<IBinder>& who);
??? // helper function to obtain camera service handle
??? static const sp<::android::hardware::ICameraService> getCameraService();
??? sp<TCamUser>???????????????????? mCamera;
??? status_t???????????????????????? mStatus;
??? sp<TCamListener>???????????????? mListener;
??? const int??????????????????????? mCameraId;
??? typedef CameraBase<TCam>???????? CameraBaseT;
};
从定义来看，这运用了模板，并使用了我们前一章定义的萃取器并设置TCamTraits = CameraTraits<TCam>，这里来获取camera特性。同时为了避免编译错误我们通知??
?typedef typename TCamTraits::TCamListener?????? TCamListener;
??? typedef typename TCamTraits::TCamUser?????????? TCamUser;
??? typedef typename TCamTraits::TCamCallbacks????? TCamCallbacks;
??? typedef typename TCamTraits::TCamConnectService TCamConnectService;
这些传过来的类型，而不是变量，便于后续的使用。后续当我们使用这个基类的时候由于未指定Tcam，后续需要指定Tcam，类似于CameraBase<TCam>.
这个类继承public IBinder::DeathRecipient通过virtual void? binderDied(const wp<IBinder>& who);用来监听binder绑定的进程是否退出。
??? class DeathRecipient : public virtual RefBase
??? {
??? public:
??????? virtual void binderDied(const wp<IBinder>& who) = 0;
};
这里虚函数的实现是在Z:\SA800U_Android9.0_R01_r220\frameworks\av\camera\CameraBase.cpp
内容如下：
template <typename TCam, typename TCamTraits>
void CameraBase<TCam, TCamTraits>::binderDied(const wp<IBinder>& /*who*/) {
??? ALOGW("mediaserver's remote binder Camera object died");
??? notifyCallback(CAMERA_MSG_ERROR, CAMERA_ERROR_SERVER_DIED, /*ext2*/0);
}
- Camera类介绍
先上定义代码如下：
Z:\SA800U_Android9.0_R01_r220\frameworks\av\include\camera\Camera.h
class Camera :
??? public CameraBase<Camera>,
??? public ::android::hardware::BnCameraClient
{
public:
??? enum {
??????? USE_CALLING_UID = ::android::hardware::ICameraService::USE_CALLING_UID
??? };
??? enum {
??????? USE_CALLING_PID = ::android::hardware::ICameraService::USE_CALLING_PID
??? };
??????????? // construct a camera client from an existing remote
??? static? sp<Camera>? create(const sp<::android::hardware::ICamera>& camera);
??? static? sp<Camera>? connect(int cameraId,
??????????????????????????????? const String16& clientPackageName,
??????????????????????????????? int clientUid, int clientPid);
??? static? status_t? connectLegacy(int cameraId, int halVersion,
???????????????????????????????????? const String16& clientPackageName,
???????????????????????????????????? int clientUid, sp<Camera>& camera);
??????????? virtual???? ~Camera();
??????????? status_t??? reconnect();
??????????? status_t??? lock();
??? ????????status_t??? unlock();
??????????? // pass the buffered IGraphicBufferProducer to the camera service
??????????? status_t??? setPreviewTarget(const sp<IGraphicBufferProducer>& bufferProducer);
??????????? // start preview mode, must call setPreviewTarget first
??????????? status_t??? startPreview();
??????????? // stop preview mode
??????????? void??????? stopPreview();
??????????? // get preview state
??????????? bool??????? previewEnabled();
??????????? // start recording mode, must call setPreviewTarget first
??????????? status_t??? startRecording();
??????????? // stop recording mode
??????????? void??????? stopRecording();
??????????? // get recording state
??????????? bool??????? recordingEnabled();
??????????? // release a recording frame
??????????? void??????? releaseRecordingFrame(const sp<IMemory>& mem);
??????????? // release a recording frame handle
??????????? void??????? releaseRecordingFrameHandle(native_handle_t *handle);
??????????? // release a batch of recording frame handles
??????????? void??????? releaseRecordingFrameHandleBatch(
??????????????????? const std::vector<native_handle_t*> handles);
??????????? // autoFocus - status returned from callback
??????????? status_t??? autoFocus();
??????????? // cancel auto focus
??????????? status_t??? cancelAutoFocus();
??????????? // take a picture - picture returned from callback
??????????? status_t??? takePicture(int msgType);
??????????? // set preview/capture parameters - key/value pairs
??????????? status_t??? setParameters(const String8& params);
??????????? // get preview/capture parameters - key/value pairs
??????????? String8???? getParameters() const;
??????????? // send command to camera driver
??????????? status_t??? sendCommand(int32_t cmd, int32_t arg1, int32_t arg2);
??????????? // Tell camera how to pass video buffers. videoBufferMode is one of VIDEO_BUFFER_MODE_*.
??????????? // Returns OK if the specified video buffer mode is supported. If videoBufferMode is
??????????? // VIDEO_BUFFER_MODE_BUFFER_QUEUE, setVideoTarget() must be called before starting
??????????? // video recording.
??????????? status_t??? setVideoBufferMode(int32_t videoBufferMode);
??????????? // Set the video buffer producer for camera to use in VIDEO_BUFFER_MODE_BUFFER_QUEUE
????????? ??// mode.
??????????? status_t??? setVideoTarget(const sp<IGraphicBufferProducer>& bufferProducer);
??????????? void??????? setListener(const sp<CameraListener>& listener);
??????????? void??????? setRecordingProxyListener(const sp<ICameraRecordingProxyListener>& listener);
??????????? // Configure preview callbacks to app. Only one of the older
??????????? // callbacks or the callback surface can be active at the same time;
??????????? // enabling one will disable the other if active. Flags can be
???? ???????// disabled by calling it with CAMERA_FRAME_CALLBACK_FLAG_NOOP, and
??????????? // Target by calling it with a NULL interface.
??????????? void??????? setPreviewCallbackFlags(int preview_callback_flag);
??????????? status_t??? setPreviewCallbackTarget(
??????????????????? const sp<IGraphicBufferProducer>& callbackProducer);
??????????? sp<ICameraRecordingProxy> getRecordingProxy();
??? // ICameraClient interface
??? virtual void??????? notifyCallback(int32_t msgType, int32_t ext, int32_t ext2);
?? ?virtual void??????? dataCallback(int32_t msgType, const sp<IMemory>& dataPtr,
???????????????????????????????????? camera_frame_metadata_t *metadata);
??? virtual void??????? dataCallbackTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr);
??? virtual void??????? recordingFrameHandleCallbackTimestamp(nsecs_t timestamp, native_handle_t* handle);
??? virtual void??????? recordingFrameHandleCallbackTimestampBatch(
??????????????????????????????? const std::vector<nsecs_t>& timestamps,
? ??????????????????????????????const std::vector<native_handle_t*>& handles);
??? class RecordingProxy : public BnCameraRecordingProxy
??? {
??? public:
??????? explicit RecordingProxy(const sp<Camera>& camera);
??????? // ICameraRecordingProxy interface
??????? virtual status_t startRecording(const sp<ICameraRecordingProxyListener>& listener);
??????? virtual void stopRecording();
??????? virtual void releaseRecordingFrame(const sp<IMemory>& mem);
??????? virtual void releaseRecordingFrameHandle(native_handle_t* handle);
??????? virtual void releaseRecordingFrameHandleBatch(
??????????????? const std::vector<native_handle_t*>& handles);
??? private:
??????? sp<Camera>???????? mCamera;
??? };
protected:
??? explicit??????????? Camera(int cameraId);
???? ???????????????????Camera(const Camera&);
??????????????????????? Camera& operator=(const Camera);
??? sp<ICameraRecordingProxyListener>? mRecordingProxyListener;
??? friend class??????? CameraBase;
};
可以看到这个类继承两个父类，其中CameraBase已经讲过了不必多述，
接下来讲一下另一个父类BnCameraClient。
- BnCameraClient
这个类是用来进行binder通信的，最终我们Camera是作为客户端需要调用binder服务端CameraService执行我们需要的动作，这里牵扯到跨进程通信，Camera Service在安卓启动过程中就会被系统拉起来等待客户端的调用。
首先看下这个类的定义：
Z:\SA800U_Android9.0_R01_r220\frameworks\av\include\camera\android\hardware\ICameraClient.h
class BnCameraClient: public android::BnInterface<ICameraClient>
{
public:
??? virtual status_t??? onTransact( uint32_t code,
??????????????????????????????????? const Parcel& data,
??????????????????????? ????????????Parcel* reply,
??????????????????????????????????? uint32_t flags = 0);
};
可以看到这个类又继承自BnInterface并传入了IcameraClient作为其模板类型，我们先来看看这个BnInterface的定义
template<typename INTERFACE>
class BnInterface : public INTERFACE, public Bbinder
{
public:
??? virtual sp<IInterface>????? queryLocalInterface(const String16& _descriptor);
??? virtual const String16&???? getInterfaceDescriptor() const;
protected:
??? virtual IBinder*??????????? onAsBinder();
};
可以看到这个类继承自INTERFACE模板参数以及继承自Bbinder，那么返回去也会就是BnCameraClient同样会继承IcameraClient，BnInterface为一个通用模板类，安卓framework native中很多服务都用到这个类，这个主要是用来进行binder通信。其中BBinder启动重要作用。
class BBinder : public Ibinder
这个类继承自Ibinder.
这部分涉及到安卓native的binder跨进程通信。
我们回到IcameraClient它的定义跟BnCameraClient在同一个文件中，定义一些CameraClient的一些功能，BnCameraClient作为跨进程服务者存在，所以它只定义一个onTransact函数。
这里使用虚函数来定义，给子类实现多态性。
这样我们大体的类关系可以梳理一下如下图：
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