android6.0源码分析之Camera API2.0下的Capture流程分析

前面对Camera2的初始化以及预览的相关流程进行了详细分析，本文将会对Camera2的capture(拍照)流程进行分析。

前面分析preview的时候，当预览成功后，会使能ShutterButton，即可以进行拍照，定位到ShutterButton的监听事件为onShutterButtonClick方法：

//CaptureModule.java@Overridepublic void onShutterButtonClick() {  //Camera未打开  if (mCamera == null) {    return;  }  int countDownDuration = mSettingsManager.getInteger(SettingsManager
　　　　.SCOPE_GLOBAL,Keys.KEY_COUNTDOWN_DURATION);  if (countDownDuration > 0) {    // 开始倒计时    mAppController.getCameraAppUI().transitionToCancel();    mAppController.getCameraAppUI().hideModeOptions();    mUI.setCountdownFinishedListener(this);    mUI.startCountdown(countDownDuration);    // Will take picture later via listener callback.  } else {    //即刻拍照    takePictureNow();  }}

首先，读取Camera的配置，判断配置是否需要延时拍照，此处分析不需延时的情况，即调用takePictureNow方法：

//CaptureModule.javaprivate void takePictureNow() {  if (mCamera == null) {    Log.i(TAG, "Not taking picture since Camera is closed.");    return;  }  //创建Capture会话并开启会话  CaptureSession session = createAndStartCaptureSession();  //获取Camera的方向  int orientation = mAppController.getOrientationManager()    .getDeviceOrientation().getDegrees();  //初始化图片参数，其中this(即CaptureModule)为PictureCallback的实现  PhotoCaptureParameters params = new PhotoCaptureParameters(      session.getTitle(), orientation, session.getLocation(),      mContext.getExternalCacheDir(), this, mPictureSaverCallback,      mHeadingSensor.getCurrentHeading(), mZoomValue, 0);  //装配Session  decorateSessionAtCaptureTime(session);  //拍照   mCamera.takePicture(params, session);}

它首先调用createAndStartCaptureSession来创建一个CaptureSession并且启动会话,这里并且会进行初始参数的设置，譬如设置CaptureModule(此处实参

为this)为图片处理的回调(后面再分析)：

//CaptureModule.javaprivate CaptureSession createAndStartCaptureSession() {  //获取会话时间  long sessionTime = getSessionTime();  //当前位置  Location location = mLocationManager.getCurrentLocation();  //设置picture name  String title = CameraUtil.instance().createJpegName(sessionTime);  //创建会话  CaptureSession session = getServices().getCaptureSessionManager()      .createNewSession(title, sessionTime, location);  //开启会话   session.startEmpty(new CaptureStats(mHdrPlusEnabled),new Size(    (int) mPreviewArea.width(), (int) mPreviewArea.height()));  return session;}

首先，获取会话的相关参数，包括会话时间，拍照的照片名字以及位置信息等，然后调用Session管理来创建CaptureSession，最后将此CaptureSession

启动。到这里，会话就创建并启动了，所以接着分析上面的拍照流程，它会调用OneCameraImpl的takePicture方法来进行拍照：

//OneCameraImpl.java@Overridepublic void takePicture(final PhotoCaptureParameters params, final CaptureSession session) {  ...  // 除非拍照已经返回，否则就广播一个未准备好状态的广播，即等待本次拍照结束  broadcastReadyState(false);  //创建一个线程  mTakePictureRunnable = new Runnable() {    @Override    public void run() {      //拍照      takePictureNow(params, session);    }  };  //设置回调，此回调后面将分析，它其实就是CaptureModule,它实现了PictureCallback  mLastPictureCallback = params.callback;  mTakePictureStartMillis = SystemClock.uptimeMillis();  //如果需要自动聚焦  if (mLastResultAFState == AutoFocusState.ACTIVE_SCAN) {    mTakePictureWhenLensIsStopped = true;  } else {    //拍照    takePictureNow(params, session);  }}

在拍照里，首先广播一个未准备好的状态广播，然后进行拍照的回调设置，并且判断是否有自动聚焦，如果是则将mTakePictureWhenLensIsStopped 设为ture，

即即刻拍照被停止了，否则则调用OneCameraImpl的takePictureNow方法来发起拍照请求：

//OneCameraImpl.javapublic void takePictureNow(PhotoCaptureParameters params, CaptureSession     session) {  long dt = SystemClock.uptimeMillis() - mTakePictureStartMillis;  try {    // 构造JPEG图片拍照的请求    CaptureRequest.Builder builder = mDevice.createCaptureRequest(      CameraDevice.TEMPLATE_STILL_CAPTURE);    builder.setTag(RequestTag.CAPTURE);    addBaselineCaptureKeysToRequest(builder);    // Enable lens-shading correction for even better DNGs.    if (sCaptureImageFormat == ImageFormat.RAW_SENSOR) {      builder.set(CaptureRequest.STATISTICS_LENS_SHADING_MAP_MODE,        CaptureRequest.STATISTICS_LENS_SHADING_MAP_MODE_ON);    } else if (sCaptureImageFormat == ImageFormat.JPEG) {      builder.set(CaptureRequest.JPEG_QUALITY, JPEG_QUALITY);        .getJpegRotation(params.orientation, mCharacteristics));    }    //用于preview的控件    builder.addTarget(mPreviewSurface);    //用于图片显示的控件    builder.addTarget(mCaptureImageReader.getSurface());    CaptureRequest request = builder.build();    if (DEBUG_WRITE_CAPTURE_DATA) {      final String debugDataDir = makeDebugDir(params.debugDataFolder,            "normal_capture_debug");      Log.i(TAG, "Writing capture data to: " + debugDataDir);      CaptureDataSerializer.toFile("Normal Capture", request,         new File(debugDataDir,"capture.txt"));    }    //拍照，mCaptureCallback为回调    mCaptureSession.capture(request, mCaptureCallback, mCameraHandler);  } catch (CameraAccessException e) {    Log.e(TAG, "Could not access camera for still image capture.");    broadcastReadyState(true);    params.callback.onPictureTakingFailed();    return;  }  synchronized (mCaptureQueue) {    mCaptureQueue.add(new InFlightCapture(params, session));  }}

与preview类似，都是通过CaptureRequest来与Camera进行通信的，通过session的capture来进行拍照，

并设置拍照的回调函数为mCaptureCallback：

//CameraCaptureSessionImpl.java@Overridepublic synchronized int capture(CaptureRequest request,CaptureCallback callback,Handler handler)throws CameraAccessException{  ...  handler = checkHandler(handler,callback);  return addPendingSequence(mDeviceImpl.capture(request,createCaptureCallbackProxy(handler,callback),mDeviceHandler));}

代码与preview中的类似，都是将请求加入到待处理的请求集，现在看CaptureCallback回调：

//OneCameraImpl.javaprivate final CameraCaptureSession.CaptureCallback mCaptureCallback = new CameraCaptureSession.CaptureCallback(){  @Override  public void onCaptureStarted(CameraCaptureSession session,CaptureRequest request,long timestamp,long frameNumber){
　　　　　//与preview类似    if(request.getTag() == RequestTag.CAPTURE&&mLastPictureCallback!=null){      mLastPictureCallback.onQuickExpose();    }  }  ...  @Override  public void onCaptureCompleted(CameraCaptureSession session,CaptureRequest request,TotalCaptureResult result){    autofocusStateChangeDispatcher(result);    if(result.get(CaptureResult.CONTROL_AF_STATE) == null){
　　　　　　　//检查自动聚焦的状态      AutoFocusHelper.checkControlAfState(result);    }    ...    if(request.getTag() == RequestTag.CAPTURE){      synchronized(mCaptureQueue){        if(mCaptureQueue.getFirst().setCaptureResult(result).isCaptureComplete()){          capture = mCaptureQueue.removeFirst();        }      }      if(capture != null){
　　　　　　　　　//拍照结束        OneCameraImpl.this.onCaptureCompleted(capture);      }    }    super.onCaptureCompleted(session,request,result);  }  ...}

这是Native层在处理请求时，会调用相应的回调，如capture开始时，会回调onCaptureStarted,具体的在preview中有过分析，当拍照结束时，会回调

onCaptureCompleted方法，其中会根据CaptureResult来检查自动聚焦的状态，并通过TAG判断其是Capture动作时，再来看它是否是队列中的第一个请求，

如果是，则将请求移除，因为请求已经处理成功，最后再调用OneCameraImpl的onCaptureCompleted方法来进行处理：

//OneCameraImpl.javaprivate void onCaptureCompleted(InFlightCapture capture){  if(isCaptureImageFormat == ImageFormat.RAW_SENSOR){    ...    File dngFile = new File(RAW_DIRECTORY,capture.session.getTitle()+".dng");    writeDngBytesAndClose(capture.image,capture.totalCaptureResult,mCharacteristics,dngFile);  }else{    //解析result中的图片数据    byte[] imageBytes = acquireJpegBytesAndClose(capture.image);    //保存Jpeg图片    saveJpegPicture(imageBytes,capture.parameters,capture.session,capture.totalCaptureResult);  }  broadcastReadyState(true);  //调用回调  capture.parameters.callback.onPictureTaken(capture.session);}

如代码所示，首先，对result中的图片数据进行了解析，然后调用saveJpegPicture方法将解析得到的图片数据进行保存，最后再调用

里面的回调(即CaptureModule，前面在初始化Parameters时说明了，它实现了PictureCallbak接口)的onPictureTaken方法，所以，

接下来先分析saveJpegPicture方法：

//OneCameraImpl.javaprivate void saveJpegPicture(byte[] jpegData,final PhotoCaptureParameters captureParams,CaptureSession session,CaptureResult result){  ...  ListenableFuture<Optional<Uri>> futureUri = session.saveAndFinish(jpegData,width,height,rotation,exif);  Futures.addCallback(futureUri,new FutureCallback<Optional<Uri>>(){    @Override    public void onSuccess(Optional<Uri> uriOptional){      captureParams.callback.onPictureSaved(mOptional.orNull());    }        @Override    public void onFailure(Throwable throwable){      captureParams.callback.onPictureSaved(null);    }  });}

它最后会回调onPictureSaved方法来对图片进行保存，所以需要分析CaptureModule的onPictureSaved方法：

//CaptureModule.java@Overridepublic void onPictureSaved(Uri uri){  mAppController.notifyNewMedia(uri);}

mAppController的实现为CameraActivity，所以分析notifyNewMedia方法：

//CameraActivity.java@Overridepublic void notifyNewMedia(Uri uri){  ...  if(FilmstripItemUtils.isMimeTypeVideo(mimeType)){
　　　　//如果拍摄的是video    sendBroadcast(new Intent(CameraUtil.ACTION_NEW_VIDEO,uri));    newData = mVideoItemFactory.queryContentUri(uri);    ...  }else if(FilmstripItemUtils.isMimeTypeImage(mimeType)){
　　　　//如果是拍摄图片     CameraUtil.broadcastNewPicture(mAppContext,uri);    newData = mPhotoItemFactory.queryCotentUri(uri);    ...  }else{    return;  }  new AsyncTask<FilmstripItem,Void,FilmstripItem>(){    @Override    protected FilmstripItem doInBackground(FilmstripItem... Params){      FilmstripItem data = params[0];      MetadataLoader.loadMetadata(getAndroidContet(),data);      return data;    }    ...  }}

由代码可知，这里有两种数据的处理，一种是video，另一种是image。而我们这里分析的是capture图片数据，所以首先会根据在回调函数

传入的参数Uri和PhotoItemFactory来查询到相应的拍照数据，然后再开启一个异步的Task来对此数据进行处理，即通过MetadataLoader的

loadMetadata来加载数据，并返回。至此，capture的流程就基本分析结束了，下面将给出capture流程的整个过程中的时序图：