关键词：
在文章android源码分析之Camera API2.0简介中，对Camera API2.0的框架以及代码做了简单介绍，本文将基于android6.0源码，分析Camera API2.0下的Camera2内置应用中，对Camera的初始化的流程分析，主要涉及Camera HAL3.0，Java 层的IPC Binder，Native层的CameraService的C/S服务架构等关键点。
Camera2相关分析文章目录：
android6.0源码分析之Camera API2.0简介
android6.0源码分析之Camera2 HAL分析
android6.0源码分析之Camera API2.0下的初始化流程分析
android6.0源码分析之Camera API2.0下的Preview(预览)流程分析
android6.0源码分析之Camera API2.0下的Capture流程分析
android6.0源码分析之Camera API2.0下的video流程分析
Camera API2.0的应用
1、Camera2初始化的应用层流程分析
Camera2的初始化流程与Camera1.0有所区别，本文将就Camera2的内置应用来分析Camera2.0的初始化过程。Camera2.0首先启动的是CameraActivity，而它继承自QuickActivity，在代码中你会发现没有重写OnCreate等生命周期方法，因为此处采用的是模板方法的设计模式，在QuickActivity中的onCreate方法调用的是onCreateTasks等方法，所以要看onCreate方法就只须看onCreateTasks方法即可：
//CameraActivity.java
@Override
public void onCreateTasks(Bundle state)
Profile profile = mProfiler.create("CameraActivity.onCreateTasks")
.start();
...
mOnCreateTime = System.currentTimeMillis();
mAppContext = getApplicationContext();
mMainHandler = new MainHandler(this, getMainLooper());
…
try
//初始化OneCameraOpener对象
①mOneCameraOpener = OneCameraModule.provideOneCameraOpener(
mFeatureConfig, mAppContext,mActiveCameraDeviceTracker,
ResolutionUtil.getDisplayMetrics(this));
mOneCameraManager = OneCameraModule.provideOneCameraManager();
catch (OneCameraException e) ...
…
//建立模块信息
②ModulesInfo.setupModules(mAppContext, mModuleManager, mFeatureConfig);
…
//进行初始化
③mCurrentModule.init(this, isSecureCamera(), isCaptureIntent());
…
如代码所示，重要的有以上三点，先看第一点：
//OneCameraModule.java
public static OneCameraOpener provideOneCameraOpener(OneCameraFeatureConfig
featureConfig, Context context, ActiveCameraDeviceTracker
activeCameraDeviceTracker,DisplayMetrics displayMetrics)
throws OneCameraException
//创建OneCameraOpener对象
Optional<OneCameraOpener> manager = Camera2OneCameraOpenerImpl.create(
featureConfig, context, activeCameraDeviceTracker, displayMetrics);
if (!manager.isPresent())
manager = LegacyOneCameraOpenerImpl.create();
...
return manager.get();
它调用Camera2OneCameraOpenerImpl的create方法来获得一个OneCameraOpener对象，以供CameraActivity之后的操作使用，继续看create方法：
//Camera2OneCameraOpenerImpl.java
public static Optional<OneCameraOpener> create(OneCameraFeatureConfig
featureConfig, Context context, ActiveCameraDeviceTracker
activeCameraDeviceTracker, DisplayMetrics displayMetrics)
...
CameraManager cameraManager;
try
cameraManager = AndroidServices.instance().provideCameraManager();
catch (IllegalStateException ex) ...
//新建一个Camera2OneCameraOpenerImpl对象
OneCameraOpener oneCameraOpener = new Camera2OneCameraOpenerImpl(
featureConfig, context, cameraManager,
activeCameraDeviceTracker, displayMetrics);
return Optional.of(oneCameraOpener);
很明显，它首先获取一个cameraManger对象，然后根据这个cameraManager对象来新创建了一个Camera2OneCameraOpenerImpl对象，所以第一步主要是为了获取一个OneCameraOpener对象，它的实现为Camera2OneCameraOpenerImpl类。
继续看第二步，ModulesInfo.setupModules:
// ModulesInfo.java
public static void setupModules(Context context, ModuleManager moduleManager,
OneCameraFeatureConfig config)
Resources res = context.getResources();
int photoModuleId = context.getResources().getInteger(
R.integer.camera_mode_photo);
//注册Photo模块
registerPhotoModule(moduleManager, photoModuleId,
SettingsScopeNamespaces.PHOTO,config.isUsingCaptureModule());
//计算你还Photo模块设置为默认的模块
moduleManager.setDefaultModuleIndex(photoModuleId);
//注册Videa模块
registerVideoModule(moduleManager, res.getInteger(
R.integer.camera_mode_video),SettingsScopeNamespaces.VIDEO);
if (PhotoSphereHelper.hasLightCycleCapture(context)) //开启闪光
//注册广角镜头
registerWideAngleModule(moduleManager, res.getInteger(
R.integer.camera_mode_panorama),SettingsScopeNamespaces
.PANORAMA);
//注册光球模块
registerPhotoSphereModule(moduleManager,res.getInteger(
R.integer.camera_mode_photosphere),
SettingsScopeNamespaces.PANORAMA);
//若需重新聚焦
if (RefocusHelper.hasRefocusCapture(context))
//注册重聚焦模块
registerRefocusModule(moduleManager, res.getInteger(
R.integer.camera_mode_refocus),
SettingsScopeNamespaces.REFOCUS);
//如果有色分离模块
if (GcamHelper.hasGcamAsSeparateModule(config))
//注册色分离模块
registerGcamModule(moduleManager, res.getInteger(
R.integer.camera_mode_gcam),SettingsScopeNamespaces.PHOTO,
config.getHdrPlusSupportLevel(OneCamera.Facing.BACK));
int imageCaptureIntentModuleId = res.getInteger(
R.integer.camera_mode_capture_intent);
registerCaptureIntentModule(moduleManager,
imageCaptureIntentModuleId,SettingsScopeNamespaces.PHOTO,
config.isUsingCaptureModule());
代码根据配置信息，进行一系列模块的注册，其中PhotoModule和VideoModule被注册，而其他的module则是根据配置来进行的，因为打开Camera应用，既可以拍照片也可以拍视频，此处，只分析PhoneModule的注册：
// ModulesInfo.java
private static void registerPhotoModule(ModuleManager moduleManager, final
int moduleId, final String namespace,
final boolean enableCaptureModule)
//向ModuleManager注册PhotoModule模块
moduleManager.registerModule(new ModuleManager.ModuleAgent()
@Override
public int getModuleId()
return moduleId;
@Override
public boolean requestAppForCamera()
return !enableCaptureModule;
@Override
public String getScopeNamespace()
return namespace;
@Override
public ModuleController createModule(AppController app, Intent
intent)
Log.v(TAG, "EnableCaptureModule = " + enableCaptureModule);
//创建ModuleController
return enableCaptureModule ? new CaptureModule(app)
: new PhotoModule(app);
);
由代码可知，它最终是由ModuleManager来新建一个CaptureModule实例，而CaptureModule其实实现了ModuleController ，即创建了一个CaptureModule模式下的ModuleController对象，而真正的CaptureModule的具体实现为ModuleManagerImpl。
至此，前两步已经获得了OneCameraOpener以及新建了ModuleController，并进行了注册，接下来分析第三步，mCurrentModule.init(this, isSecureCamera(), isCaptureIntent()):
//CaptureModule.java
public void init(CameraActivity activity, boolean isSecureCamera, boolean
isCaptureIntent)
...
HandlerThread thread = new HandlerThread("CaptureModule.mCameraHandler");
thread.start();
mCameraHandler = new Handler(thread.getLooper());
//获取第一步中创建的OneCameraOpener对象
mOneCameraOpener = mAppController.getCameraOpener();
try
//获取前面创建的OneCameraManager对象
mOneCameraManager = OneCameraModule.provideOneCameraManager();
catch (OneCameraException e)
Log.e(TAG, "Unable to provide a OneCameraManager. ", e);
`...
//新建CaptureModule的UI
mUI = new CaptureModuleUI(activity, mAppController.
getModuleLayoutRoot(), mUIListener);
//设置预览状态的监听
mAppController.setPreviewStatusListener(mPreviewStatusListener);
synchronized (mSurfaceTextureLock)
//获取SurfaceTexture
mPreviewSurfaceTexture = mAppController.getCameraAppUI()
.getSurfaceTexture();
首先获取前面创建的OneCameraOpener对象以及OneCameraManager对象，然后再设置预览状态监听，这里主要分析预览状态的监听：
//CaptureModule.java
private final PreviewStatusListener mPreviewStatusListener = new
PreviewStatusListener()
...
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface,
int width, int height)
updatePreviewTransform(width, height, true);
synchronized (mSurfaceTextureLock)
mPreviewSurfaceTexture = surface;
//打开Camera
reopenCamera();
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface)
Log.d(TAG, "onSurfaceTextureDestroyed");
synchronized (mSurfaceTextureLock)
mPreviewSurfaceTexture = null;
//关闭Camera
closeCamera();
return true;
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface,
int width, int height)
//更新预览尺寸
updatePreviewBufferSize();
...
;由代码可知，当SurfaceTexture的状态变成可用的时候，会调用reopenCamera()方法来打开Camera，所以继续分析reopenCamera()方法：
//CaptureModule.java
private void reopenCamera()
if (mPaused)
return;
AsyncTask.THREAD_POOL_EXECUTOR.execute(new Runnable()
@Override
public void run()
closeCamera();
if(!mAppController.isPaused())
//开启Camera并开始预览
openCameraAndStartPreview();
);
它采用异步任务的方法，开启一个异步线程来进行启动操作，首先关闭打开的Camera，然后如果AppController不处于暂停状态，则打开Camera并启动Preview操作，所以继续分析openCameraAndStartPreview方法：
//CaptureModule.java
private void openCameraAndStartPreview()
...
if (mOneCameraOpener == null)
Log.e(TAG, "no available OneCameraManager, showing error dialog");
//释放CameraOpenCloseLock锁
mCameraOpenCloseLock.release();
mAppController.getFatalErrorHandler().onGenericCameraAccessFailure();
guard.stop("No OneCameraManager");
return;
// Derive objects necessary for camera creation.
MainThread mainThread = MainThread.create();
//查找需要打开的CameraId
CameraId cameraId = mOneCameraManager.findFirstCameraFacing(
mCameraFacing);
...
//打开Camera
mOneCameraOpener.open(cameraId, captureSetting, mCameraHandler,
mainThread, imageRotationCalculator, mBurstController,
mSoundPlayer,new OpenCallback()
@Override
public void onFailure()
//进行失败的处理
...
@Override
public void onCameraClosed()
...
@Override
public void onCameraOpened(@Nonnull final OneCamera camera)
Log.d(TAG, "onCameraOpened: " + camera);
mCamera = camera;
if (mAppController.isPaused())
onFailure();
return;
...
mMainThread.execute(new Runnable()
@Override
public void run()
//通知UI，Camera状态变化
mAppController.getCameraAppUI().onChangeCamera();
//使能拍照按钮
mAppController.getButtonManager().enableCameraButton();
);
//至此，Camera打开成功，开始预览
camera.startPreview(new Surface(getPreviewSurfaceTexture()),
new CaptureReadyCallback()
@Override
public void onSetupFailed()
...
@Override
public void onReadyForCapture()
//释放锁
mCameraOpenCloseLock.release();
mMainThread.execute(new Runnable()
@Override
public void run()
...
onPreviewStarted();
...
onReadyStateChanged(true);
//设置CaptureModule为Capture准备的状态监听
mCamera.setReadyStateChangedListener(
CaptureModule.this);
mUI.initializeZoom(mCamera.getMaxZoom());
mCamera.setFocusStateListener(
CaptureModule.this);
);
);
, mAppController.getFatalErrorHandler());
guard.stop("mOneCameraOpener.open()");
首先，它主要会调用Camera2OneCameraOpenerImpl的open方法来打开Camera，并定义了开启的回调函数，对开启结束后的结果进行处理，如失败则释放mCameraOpenCloseLock，并暂停mAppController，如果打开成功，通知UI成功，并开启Camera的Preview，并且定义了Preview的各种回调操作，这里主要分析Open过程，所以继续分析：
//Camera2OneCameraOpenerImpl.java
@Override
public void open(
...
mActiveCameraDeviceTracker.onCameraOpening(cameraKey);
//打开Camera，此处调用框架层的CameraManager类的openCamera，进入frameworks层
mCameraManager.openCamera(cameraKey.getValue(),
new CameraDevice.StateCallback()
private boolean isFirstCallback = true;
@Override
...
@Override
public void onOpened(CameraDevice device)
//第一次调用此回调
if (isFirstCallback)
isFirstCallback = false;
try
CameraCharacteristics characteristics = mCameraManager
.getCameraCharacteristics(device.getId());
...
//创建OneCamera对象
OneCamera oneCamera = OneCameraCreator.create(device,
characteristics, mFeatureConfig, captureSetting,
mDisplayMetrics, mContext, mainThread,
imageRotationCalculator, burstController, soundPlayer,
fatalErrorHandler);
if (oneCamera != null)
//如果oneCamera不为空，则回调onCameraOpened，后面将做分析
openCallback.onCameraOpened(oneCamera);
else
...
openCallback.onFailure();
catch (CameraAccessException e)
openCallback.onFailure();
catch (OneCameraAccessException e)
Log.d(TAG, "Could not create OneCamera", e);
openCallback.onFailure();
, handler);
...
至此，Camera的初始化流程中应用层的分析就差不多了，下一步将会调用CameraManager的openCamera方法来进入框架层，并进行Camera的初始化，下面将应用层的初始化时序图：
2、Camera2初始化的框架层流程分析
由上面的分析可知，将由应用层进入到框架层处理，将会调用CameraManager的openCamera方法，并且定义了CameraDevice的状态回调函数，具体的回调操作此处不做分析，继续跟踪openCamera()方法：
//CameraManager.java(frameworks/base/core/java/android/hardware/camera2)
@RequiresPermission(android.Manifest.permission.CAMERA)
public void openCamera(@NonNull String cameraId,@NonNull final
CameraDevice.StateCallback callback, @Nullable Handler handler)
throws CameraAccessException
...
openCameraDeviceUserAsync(cameraId, callback, handler);
由代码可知，此处与Camera1.0有明显不同，Camera1.0是通过一个异步的线程以及JNI来调用android_hardware_camera.java里面的native_setup方法来连接Camera，其使用的是C++的Binder来与CameraService进行通信的，而此处则不一样，它直接使用的是Java层的Binder来进行通信，先看openCameraDeviceUserAsync代码:
//CameraManager.java(frameworks/base/core/java/android/hardware/camera2)
private CameraDevice openCameraDeviceUserAsync(String cameraId,
CameraDevice.StateCallback callback, Handler handler)
throws CameraAccessException
CameraCharacteristics characteristics = getCameraCharacteristics(
cameraId);
CameraDevice device = null;
try
synchronized (mLock)
ICameraDeviceUser cameraUser = null;
//初始化一个CameraDevice对象
android.hardware.camera2.impl.CameraDeviceImpl deviceImpl =
new android.hardware.camera2.impl.CameraDeviceImpl(cameraId,
callback, handler, characteristics);
BinderHolder holder = new BinderHolder();
//获取回调
ICameraDeviceCallbacks callbacks = deviceImpl.getCallbacks();
int id = Integer.parseInt(cameraId);
try
if (supportsCamera2ApiLocked(cameraId))
//通过Java层的Binder获取CameraService
ICameraService cameraService = CameraManagerGlobal.get()
.getCameraService();
...
//通过CameraService连接Camera设备
cameraService.connectDevice(callbacks, id, mContext
.getOpPackageName(), USE_CALLING_UID, holder);
//获取连接成功的CameraUser对象，它用来与CameraService通信
cameraUser = ICameraDeviceUser.Stub.asInterface(
holder.getBinder());
else
//使用遗留的API
cameraUser = CameraDeviceUserShim.connectBinderShim(
callbacks, id);
catch (CameraRuntimeException e)
...
catch (RemoteException e)
...
//将其包装成DeviceImpl对象，供应用层使用
deviceImpl.setRemoteDevice(cameraUser);
device = deviceImpl;
catch (NumberFormatException e)
...
catch (CameraRuntimeException e)
throw e.asChecked();
return device;
此方法的目的是通过CameraService来连接并获取CameraDevice对象，该对象用来与Camera进行通信操作。代码首先通过Java层的Binder机制获取CameraService，然后调用其connectDevice方法来连接CaneraDevice，最后Camera返回的是CameraDeviceUser对象，而接着将其封装成Jav层CameraDevice对象，而之后所有与Camera的通信都通过CameraDevice的接口来进行。接下来分析一下Native层下的CameraDevice的初始化过程：
//CameraService.cpp，其中device为输出对象
status_t CameraService::connectDevice(const sp<ICameraDeviceCallbacks>& cameraCb,int cameraId,
const String16& clientPackageName,int clientUid,/*out*/sp<ICameraDeviceUser>& device)
status_t ret = NO_ERROR;
String8 id = String8::format("%d", cameraId);
sp<CameraDeviceClient> client = nullptr;
ret = connectHelper<ICameraDeviceCallbacks,CameraDeviceClient>(cameraCb, id,
CAMERA_HAL_API_VERSION_UNSPECIFIED, clientPackageName, clientUid, API_2, false, false,
/*out*/client);//client为输出对象
...
device = client;
return NO_ERROR;
Native层的connectDevice方法就是调用了connectHelper方法，所以继续分析connectHelper：
//CameraService.h
template<class CALLBACK, class CLIENT>
status_t CameraService::connectHelper(const sp<CALLBACK>& cameraCb, const String8& cameraId,
int halVersion, const String16& clientPackageName, int clientUid,
apiLevel effectiveApiLevel, bool legacyMode, bool shimUpdateOnly,
/*out*/sp<CLIENT>& device)
status_t ret = NO_ERROR;
String8 clientName8(clientPackageName);
int clientPid = getCallingPid();
...
sp<CLIENT> client = nullptr;
...
//如果有必要，给FlashLight关闭设备的机会
mFlashlight->prepareDeviceOpen(cameraId);
//获取CameraId
int id = cameraIdToInt(cameraId);
...
//获取Device的版本，此处为Device3
int deviceVersion = getDeviceVersion(id, /*out*/&facing);
sp<BasicClient> tmp = nullptr;
//获取client对象
if((ret = makeClient(this, cameraCb, clientPackageName, cameraId, facing, clientPid,
clientUid, getpid(), legacyMode, halVersion, deviceVersion, effectiveApiLevel,
/*out*/&tmp)) != NO_ERROR)
return ret;
client = static_cast<CLIENT*>(tmp.get());
//调用client的初始化函数来初始化模块
if ((ret = client->initialize(mModule)) != OK)
ALOGE("%s: Could not initialize client from HAL module.", __FUNCTION__);
return ret;
sp<IBinder> remoteCallback = client->getRemote();
if (remoteCallback != nullptr)
remoteCallback->linkToDeath(this);
// lock is destroyed, allow further connect calls
//将client赋值给输出Device
device = client;
return NO_ERROR;
CameraService根据Camera的相关参数来获取一个client，如makeClient方法，然后再调用client的initialize来进行初始化，首先看makeClient：
//CameraService.cpp
status_t CameraService::makeClient(const sp<CameraService>& cameraService,
const sp<IInterface>& cameraCb, const String16& packageName, const String8& cameraId,
int facing, int clientPid, uid_t clientUid, int servicePid, bool legacyMode,
int halVersion, int deviceVersion, apiLevel effectiveApiLevel,
/*out*/sp<BasicClient>* client)
//将字符串的CameraId转换成整形
int id = cameraIdToInt(cameraId);
...
if (halVersion < 0 || halVersion == deviceVersion) //判断Camera HAL版本是否和Device的版本相同
switch(deviceVersion)
case CAMERA_DEVICE_API_VERSION_1_0:
if (effectiveApiLevel == API_1) // Camera1 API route
sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
*client = new CameraClient(cameraService, tmp, packageName, id, facing,
clientPid, clientUid, getpid(), legacyMode);
else // Camera2 API route
ALOGW("Camera using old HAL version: %d", deviceVersion);
return -EOPNOTSUPP;
break;
case CAMERA_DEVICE_API_VERSION_2_0:
case CAMERA_DEVICE_API_VERSION_2_1:
case CAMERA_DEVICE_API_VERSION_3_0:
case CAMERA_DEVICE_API_VERSION_3_1:
case CAMERA_DEVICE_API_VERSION_3_2:
case CAMERA_DEVICE_API_VERSION_3_3:
if (effectiveApiLevel == API_1) // Camera1 API route
sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
*client = new Camera2Client(cameraService, tmp, packageName, id, facing,
clientPid, clientUid, servicePid, legacyMode);
else // Camera2 API route
sp<ICameraDeviceCallbacks> tmp =
static_cast<ICameraDeviceCallbacks*>(cameraCb.get());
*client = new CameraDeviceClient(cameraService, tmp, packageName, id,
facing, clientPid, clientUid, servicePid);
break;
default:
// Should not be reachable
ALOGE("Unknown camera device HAL version: %d", deviceVersion);
return INVALID_OPERATION;
else
// A particular HAL version is requested by caller. Create CameraClient
// based on the requested HAL version.
if (deviceVersion > CAMERA_DEVICE_API_VERSION_1_0 &&
halVersion == CAMERA_DEVICE_API_VERSION_1_0)
// Only support higher HAL version device opened as HAL1.0 device.
sp<ICameraClient> tmp = static_cast<ICameraClient*>(cameraCb.get());
*client = new CameraClient(cameraService, tmp, packageName, id, facing,
clientPid, clientUid, servicePid, legacyMode);
else
// Other combinations (e.g. HAL3.x open as HAL2.x) are not supported yet.
ALOGE("Invalid camera HAL version %x: HAL %x device can only be"
" opened as HAL %x device", halVersion, deviceVersion,
CAMERA_DEVICE_API_VERSION_1_0);
return INVALID_OPERATION;
return NO_ERROR;
其中就是创建一个Client对象，由于此处分析的是Camera API2.0，其HAL的版本是3.0+，而Device的版本则其Device的版本即为3.0+，所以会创建一个CameraDeviceClient对象，至此，makeClient已经创建了client对象，并返回了，接着看它的初始化：
//CameraDeviceClient.cpp
status_t CameraDeviceClient::initialize(CameraModule *module)
ATRACE_CALL();
status_t res;
//调用Camera2ClientBase的初始化函数来初始化CameraModule模块
res = Camera2ClientBase::initialize(module);
if (res != OK)
return res;
String8 threadName;
//初始化FrameProcessor
mFrameProcessor = new FrameProcessorBase(mDevice);
threadName = String8::format("CDU-%d-FrameProc", mCameraId);
mFrameProcessor->run(threadName.string());
//并注册监听，监听的实现就在CameraDeviceClient类中
mFrameProcessor->registerListener(FRAME_PROCESSOR_LISTENER_MIN_ID,
FRAME_PROCESSOR_LISTENER_MAX_ID, /*listener*/this,/*sendPartials*/true);
return OK;
它会调用Camera2ClientBase的initialize方法来初始化，并且会初始化一个FrameProcessor来进行帧处理，主要是回调每一帧的ExtraResult到应用中，也就是3A相关的数据信息。而Camera1.0中各种Processor模块，即将数据打包处理后再返回到应用的模块都已经不存在，而Camera2.0中将由MediaRecorder、SurfaceView、ImageReader等来直接处理，总体来说效率更好。继续看initialize：
// Camera2ClientBase.cpp
template <typename TClientBase>
status_t Camera2ClientBase<TClientBase>::initialize(CameraModule *module)
...
//调用Device的initialie方法
res = mDevice->initialize(module);
...
res = mDevice->setNotifyCallback(this);
return OK;
代码就是调用了Device的initialize方法，此处的Device是在Camera2ClientBase的构造函数中创建的：
// Camera2ClientBase.cpp
template <typename TClientBase>
Camera2ClientBase<TClientBase>::Camera2ClientBase(const sp<CameraService>& cameraService,
const sp<TCamCallbacks>& remoteCallback,const String16& clientPackageName,
int cameraId,int cameraFacing,int clientPid,uid_t clientUid,int servicePid):
TClientBase(cameraService, remoteCallback, clientPackageName,cameraId, cameraFacing,
clientPid, clientUid, servicePid),mSharedCameraCallbacks(remoteCallback),
mDeviceVersion(cameraService->getDeviceVersion(cameraId))
...
mInitialClientPid = clientPid;
mDevice = CameraDeviceFactory::createDevice(cameraId);
...
目前Camera API是2.0，而Device的API已经是3.0+了，继续看CameraDeviceFactory的createDevice方法：
// CameraDeviceFactory.cpp
sp<CameraDeviceBase> CameraDeviceFactory::createDevice(int cameraId)
sp<CameraService> svc = sService.promote();
...
int deviceVersion = svc->getDeviceVersion(cameraId, /*facing*/NULL);
sp<CameraDeviceBase> device;
switch (deviceVersion)
case CAMERA_DEVICE_API_VERSION_2_0:
case CAMERA_DEVICE_API_VERSION_2_1:
device = new Camera2Device(cameraId);
break;
case CAMERA_DEVICE_API_VERSION_3_0:
case CAMERA_DEVICE_API_VERSION_3_1:
case CAMERA_DEVICE_API_VERSION_3_2:
case CAMERA_DEVICE_API_VERSION_3_3:
device = new Camera3Device(cameraId);
break;
default:
ALOGE("%s: Camera %d: Unknown HAL device version %d",
__FUNCTION__, cameraId, deviceVersion);
device = NULL;
break;
return device;
很显然，它将会创建一个Camera3Device对象，所以，Device的initialize就是调用了Camera3Device的initialize方法：
// Camera3Device.cpp
status_t Camera3Device::initialize(CameraModule *module)
...
camera3_device_t *device;
//打开Camera HAL层的Deivce
res = module->open(deviceName.string(),
reinterpret_cast<hw_device_t**>(&device));
...
//交叉检查Device的版本
if (device->common.version < CAMERA_DEVICE_API_VERSION_3_0)
SET_ERR_L("Could not open camera: "
"Camera device should be at least %x, reports %x instead",
CAMERA_DEVICE_API_VERSION_3_0,
device->common.version);
device->common.close(&device->common);
return BAD_VALUE;
...
//调用回调函数来进行初始化，即调用打开Device的initialize方法来进行初始化
res = device->ops->initialize(device, this);
...
//启动请求队列线程
mRequestThread = new RequestThread(this, mStatusTracker, device, aeLockAvailable);
res = mRequestThread->run(String8::format("C3Dev-%d-ReqQueue", mId).string());
if (res != OK)
SET_ERR_L("Unable to start request queue thread: %s (%d)",
strerror(-res), res);
device->common.close(&device->common);
mRequestThread.clear();
return res;
...
//返回初始成功
return OK;
首先，会依赖HAL框架打开并获得相应的Device对象，具体的流程请参考android6.0源码分析之Camera2 HAL分析，然后再回调此对象的initialize方法进行初始化，最后再启动RequestThread等线程，并返回initialize成功。至此Camera API2.0下的初始化过程就分析结束了。框架层的初始化时序图如下：
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