Android Camera数据流分析全程记录（overlay方式）

 Android Camera数据流分析全程记录（overlay方式）

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这里为什么要研究overlay方式呢？android camera需要driver和app层需要有大量数据需要传输，如果使用非overlay方式进行数据从driver到app层的传输，使系统性能受到很到影响，使系统速度变慢，同时会影响功耗等，而在camera preview module时，通常我们是不必要将采集的数据保存下来的，而不像录像module下，需要将数据保存下来，所以overlay方式就是不经过数据回传，直接显示从driver的数据方式，采用这种方式app从无法获取到数据，所以这种方式应用在preview方式下

这里我是针对android4.0版本的，相对android2.x版本的overlay已经发生了很大的变化，想要研究这方面的可以自己去了解一下，这里不再多说了

开始部分我就直接在这里带过了，系统初始打开camera时，调用到app的onCreate方法，这里主要做了一下工作：
1.开始一个openCamera线程打开camera
2.实例化很多的对象，用于camera工作使用
3.实例化surfaceview和surfaceholder,并且填充了其中的surfacechanged，surfacedestoryed和surfacecreated这三个方式
4.开始一个preview线程用于preview过程
这其中3.4是我们这里要关注的重点，上面实例化了这个surfaceview将决定了我们到底是否使用overlay方式
在这里第三遍完成之后，系统会自动执行surfacechanged这个方式，每次显示区域发生改变都会自动调用这个方法，刚开始打开camera时，显示区域从无到有，因此必要这里会想调用到surfacechanged方法
我们就还是看看在这里都做了些什么事情

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // Make sure we have a surface in the holder before proceeding.
        if (holder.getSurface() == null) {
            Log.d(TAG, "holder.getSurface() == null");
            return;
        }

        Log.v(TAG, "surfaceChanged. w=" + w + ". h=" + h);

        // We need to save the holder for later use, even when the mCameraDevice
        // is null. This could happen if onResume() is invoked after this
        // function.
        mSurfaceHolder = holder;

        // The mCameraDevice will be null if it fails to connect to the camera
        // hardware. In this case we will show a dialog and then finish the
        // activity, so it's OK to ignore it.
        if (mCameraDevice == null) return;

        // Sometimes surfaceChanged is called after onPause or before onResume.
        // Ignore it.
        if (mPausing || isFinishing()) return;

        setSurfaceLayout();

        // Set preview display if the surface is being created. Preview was
        // already started. Also restart the preview if display rotation has
        // changed. Sometimes this happens when the device is held in portrait
        // and camera app is opened. Rotation animation takes some time and
        // display rotation in onCreate may not be what we want.
        if (mCameraState == PREVIEW_STOPPED) {//这里表示第一次打开camera时，那么调用startpreview
            startPreview(true);
            startFaceDetection();
        } else {//这里则表示camera已经打开过程中发生的显示变化，比如横屏竖频转换，所以zheli只需要重新设置previewdisplay
            if (Util.getDisplayRotation(this) != mDisplayRotation) {
                setDisplayOrientation();
            }
            if (holder.isCreating()) {
                // Set preview display if the surface is being created and preview
                // was already started. That means preview display was set to null
                // and we need to set it now.
                setPreviewDisplay(holder);
            }
        }

        // If first time initialization is not finished, send a message to do
        // it later. We want to finish surfaceChanged as soon as possible to let
        // user see preview first.
        if (!mFirstTimeInitialized) {
            mHandler.sendEmptyMessage(FIRST_TIME_INIT);
        } else {
            initializeSecondTime();
        }

        SurfaceView preview = (SurfaceView) findViewById(R.id.camera_preview);
        CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];
        boolean mirror = (info.facing == CameraInfo.CAMERA_FACING_FRONT);
        int displayRotation = Util.getDisplayRotation(this);
        int displayOrientation = Util.getDisplayOrientation(displayRotation, mCameraId);

        mTouchManager.initialize(preview.getHeight() / 3, preview.getHeight() / 3,
               preview, this, mirror, displayOrientation);

    }

从上面代码我们必须知道，在surface发生变化时必须调用 setPreviewDisplay，根据之后的学习，在startpreview方式中真正startpreview之前同样要调用 setPreviewDisplay，在 setPreviewDisplay的方法中完成了很多初始化，也是在这里决定是否使用overlay方式的，我们就先看看startpreview这个方法吧

private void startPreview(boolean updateAll) {
        if (mPausing || isFinishing()) return;

        mFocusManager.resetTouchFocus();

        mCameraDevice.setErrorCallback(mErrorCallback);

        // If we're previewing already, stop the preview first (this will blank
        // the screen).
        if (mCameraState != PREVIEW_STOPPED) stopPreview();

        setPreviewDisplay(mSurfaceHolder);
        setDisplayOrientation();

        if (!mSnapshotOnIdle) {
            // If the focus mode is continuous autofocus, call cancelAutoFocus to
            // resume it because it may have been paused by autoFocus call.
            if (Parameters.FOCUS_MODE_CONTINUOUS_PICTURE.equals(mFocusManager.getFocusMode())) {
                mCameraDevice.cancelAutoFocus();
            }
            mFocusManager.setAeAwbLock(false); // Unlock AE and AWB.
        }

        if ( updateAll ) {
            Log.v(TAG, "Updating all parameters!");
            setCameraParameters(UPDATE_PARAM_INITIALIZE | UPDATE_PARAM_ZOOM | UPDATE_PARAM_PREFERENCE);
        } else {
            setCameraParameters(UPDATE_PARAM_MODE);
        }

        //setCameraParameters(UPDATE_PARAM_ALL);

        // Inform the mainthread to go on the UI initialization.
        if (mCameraPreviewThread != null) {
            synchronized (mCameraPreviewThread) {
                mCameraPreviewThread.notify();
            }
        }

        try {
            Log.v(TAG, "startPreview");
            mCameraDevice.startPreview();
        } catch (Throwable ex) {
            closeCamera();
            throw new RuntimeException("startPreview failed", ex);
        }

        mZoomState = ZOOM_STOPPED;
        setCameraState(IDLE);
        mFocusManager.onPreviewStarted();
        if ( mTempBracketingEnabled ) {
            mFocusManager.setTempBracketingState(FocusManager.TempBracketingStates.ACTIVE);
        }

        if (mSnapshotOnIdle) {
            mHandler.post(mDoSnapRunnable);
        }
    }

上面大家看到了，先调用了 setPreviewDisplay，最后调用 mCameraDevice . startPreview ( )开始preview
这里过程如下：app-->frameworks-->JNI-->camera client-->camera service-->hardware interface-->HAL
1. setPreviewDisplay方法调用时在app层最初的传入的参数是surfaceholder结构
2.到了JNI层 setPreviewDisplay方法传入的参数已经是surface结构了
3.到了camera service层
    sp<IBinder> binder(surface != 0 ? surface->asBinder() : 0);
    sp<ANativeWindow> window(surface);
    return setPreviewWindow(binder, window);
    通过上面的转换调用同名不同参数的另外一个方法，到这里调用的参数已经转变为IBinder和ANativeWindow
4.调用hardware interface的setPreviewWindow(window)，这里只有一个 ANativeWindow类型的参数
5.到了camerahal_module中转站时又发生了变化，看看下面的定义，参数变为 preview_stream_ops 这个类型的结构
    int camera_set_preview_window(struct camera_device * device, struct preview_stream_ops *window)
上面过程参数类型一直在变化，不过从app层一直传到这里，其实是对同一个内存地址的传输，就像张三换了身衣服，但是他还是张三一样
现在我们就直接看看HAL层的实现

/**
   @brief Sets ANativeWindow object.

   Preview buffers provided to CameraHal via this object. DisplayAdapter will be interfacing with it
   to render buffers to display.

   @param[in] window The ANativeWindow object created by Surface flinger
   @return NO_ERROR If the ANativeWindow object passes validation criteria
   @todo Define validation criteria for ANativeWindow object. Define error codes for scenarios

 */
status_t CameraHal::setPreviewWindow(struct preview_stream_ops *window)
{
    status_t ret = NO_ERROR;
    CameraAdapter::BuffersDescriptor desc;

    LOG_FUNCTION_NAME;
    mSetPreviewWindowCalled = true;

   ///If the Camera service passes a null window, we destroy existing window and free the DisplayAdapter
    if(!window)//这种情况下，window是null，表示不采用overlay方式，则不需要新建displayadapter
    {
        if(mDisplayAdapter.get() != NULL)
        {
            ///NULL window passed, destroy the display adapter if present
            CAMHAL_LOGD("NULL window passed, destroying display adapter");
            mDisplayAdapter.clear();
            ///@remarks If there was a window previously existing, we usually expect another valid window to be passed by the client
            ///@remarks so, we will wait until it passes a valid window to begin the preview again
            mSetPreviewWindowCalled = false;
        }
        CAMHAL_LOGD("NULL ANativeWindow passed to setPreviewWindow");
        return NO_ERROR;
    }else if(mDisplayAdapter.get() == NULL)//传入的window不是null，但是还没有未使用overlay方式创建displayadapter，创建displayadapter
    {
        // Need to create the display adapter since it has not been created
        // Create display adapter
        mDisplayAdapter = new ANativeWindowDisplayAdapter();
        ret = NO_ERROR;
        if(!mDisplayAdapter.get() || ((ret=mDisplayAdapter->initialize())!=NO_ERROR))
        {
            if(ret!=NO_ERROR)
            {
                mDisplayAdapter.clear();
                CAMHAL_LOGEA("DisplayAdapter initialize failed");
                LOG_FUNCTION_NAME_EXIT;
                return ret;
            }
            else
            {
                CAMHAL_LOGEA("Couldn't create DisplayAdapter");
                LOG_FUNCTION_NAME_EXIT;
                return NO_MEMORY;
            }
        }

        // DisplayAdapter needs to know where to get the CameraFrames from inorder to display
        // Since CameraAdapter is the one that provides the frames, set it as the frame provider for DisplayAdapter
        mDisplayAdapter->setFrameProvider(mCameraAdapter);

        // Any dynamic errors that happen during the camera use case has to be propagated back to the application
        // via CAMERA_MSG_ERROR. AppCallbackNotifier is the class that notifies such errors to the application
        // Set it as the error handler for the DisplayAdapter
        mDisplayAdapter->setErrorHandler(mAppCallbackNotifier.get());

        // Update the display adapter with the new window that is passed from CameraService
        ret = mDisplayAdapter->setPreviewWindow(window);
        if(ret!=NO_ERROR)
            {
            CAMHAL_LOGEB("DisplayAdapter setPreviewWindow returned error %d", ret);
            }

        if(mPreviewStartInProgress)
        {
            CAMHAL_LOGDA("setPreviewWindow called when preview running");
            // Start the preview since the window is now available
            ret = startPreview();
        }
    } else {//传入的window不是null，并且displaadaper已经创建好，那么这里只需要将新的window与已经创建好的displayadapter关联即可
        // Update the display adapter with the new window that is passed from CameraService
        ret = mDisplayAdapter->setPreviewWindow(window);
        if ( (NO_ERROR == ret) && previewEnabled() ) {
            restartPreview();
        } else if (ret == ALREADY_EXISTS) {
            // ALREADY_EXISTS should be treated as a noop in this case
            ret = NO_ERROR;
        }
    }
    LOG_FUNCTION_NAME_EXIT;

    return ret;

}

这里我们重点看看新建displayadapter的过程：
1.实例化一个 ANativeWindowDisplayAdapter 对象
2. mDisplayAdapter - > initialize ( )
3. mDisplayAdapter - > setFrameProvider ( mCameraAdapter )//这一步是关键，之后会遇到的
4. mDisplayAdapter - > setErrorHandler ( mAppCallbackNotifier . get ( ) )
5. mDisplayAdapter - > setPreviewWindow ( window ) ;
做完了上面这些步骤之后，就是startpreview了

/**
   @brief Start preview mode.

   @param none
   @return NO_ERROR Camera switched to VF mode
   @todo Update function header with the different errors that are possible

 */
status_t CameraHal::startPreview() {
    LOG_FUNCTION_NAME;

    // When tunneling is enabled during VTC, startPreview happens in 2 steps:
    // When the application sends the command CAMERA_CMD_PREVIEW_INITIALIZATION,
    // cameraPreviewInitialization() is called, which in turn causes the CameraAdapter
    // to move from loaded to idle state. And when the application calls startPreview,
    // the CameraAdapter moves from idle to executing state.
    //
    // If the application calls startPreview() without sending the command
    // CAMERA_CMD_PREVIEW_INITIALIZATION, then the function cameraPreviewInitialization()
    // AND startPreview() are executed. In other words, if the application calls
    // startPreview() without sending the command CAMERA_CMD_PREVIEW_INITIALIZATION,
    // then the CameraAdapter moves from loaded to idle to executing state in one shot.
    status_t ret = cameraPreviewInitialization();

    // The flag mPreviewInitializationDone is set to true at the end of the function
    // cameraPreviewInitialization(). Therefore, if everything goes alright, then the
    // flag will be set. Sometimes, the function cameraPreviewInitialization() may
    // return prematurely if all the resources are not available for starting preview.
    // For example, if the preview window is not set, then it would return NO_ERROR.
    // Under such circumstances, one should return from startPreview as well and should
    // not continue execution. That is why, we check the flag and not the return value.
    if (!mPreviewInitializationDone) return ret;

    // Once startPreview is called, there is no need to continue to remember whether
    // the function cameraPreviewInitialization() was called earlier or not. And so
    // the flag mPreviewInitializationDone is reset here. Plus, this preserves the
    // current behavior of startPreview under the circumstances where the application
    // calls startPreview twice or more.
    mPreviewInitializationDone = false;

    ///Enable the display adapter if present, actual overlay enable happens when we post the buffer
    if(mDisplayAdapter.get() != NULL) {
        CAMHAL_LOGDA("Enabling display");
        int width, height;
        mParameters.getPreviewSize(&width, &height);

#if PPM_INSTRUMENTATION || PPM_INSTRUMENTATION_ABS
        ret = mDisplayAdapter->enableDisplay(width, height, &mStartPreview);
#else
        ret = mDisplayAdapter->enableDisplay(width, height, NULL);
#endif

        if ( ret != NO_ERROR ) {
            CAMHAL_LOGEA("Couldn't enable display");

            // FIXME: At this stage mStateSwitchLock is locked and unlock is supposed to be called
            // only from mCameraAdapter->sendCommand(CameraAdapter::CAMERA_START_PREVIEW)
            // below. But this will never happen because of goto error. Thus at next
            // startPreview() call CameraHAL will be deadlocked.
            // Need to revisit mStateSwitch lock, for now just abort the process.
            CAMHAL_ASSERT_X(false,
                "At this stage mCameraAdapter->mStateSwitchLock is still locked, "
                "deadlock is guaranteed");

            goto error;
        }

    }

    ///Send START_PREVIEW command to adapter
    CAMHAL_LOGDA("Starting CameraAdapter preview mode");

    ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_START_PREVIEW);

    if(ret!=NO_ERROR) {
        CAMHAL_LOGEA("Couldn't start preview w/ CameraAdapter");
        goto error;
    }
    CAMHAL_LOGDA("Started preview");

    mPreviewEnabled = true;
    mPreviewStartInProgress = false;
    return ret;

    error:

        CAMHAL_LOGEA("Performing cleanup after error");

        //Do all the cleanup
        freePreviewBufs();
        mCameraAdapter->sendCommand(CameraAdapter::CAMERA_STOP_PREVIEW);
        if(mDisplayAdapter.get() != NULL) {
            mDisplayAdapter->disableDisplay(false);
        }
        mAppCallbackNotifier->stop();
        mPreviewStartInProgress = false;
        mPreviewEnabled = false;
        LOG_FUNCTION_NAME_EXIT;

        return ret;
}

上面标出的 cameraPreviewInitialization ( )方法也十分关键，之前已经说过，之后如果需要会再做说明
Enable the display adapter  if  present ,  actual overlay enable happens when we post the buffer
说明如果display adapter不是null，这里会enable，overlay方式就启动了
我们接着往下看，看看driver获取的数据到底是怎样处理的，startpreview会通过camerahal-->cameraapapter-->V4Lcameradapter
调用到v4l2层的startpreview，下面看看他的具体是实现

status_t V4LCameraAdapter::startPreview()
{
    status_t ret = NO_ERROR;

    LOG_FUNCTION_NAME;
    Mutex::Autolock lock(mPreviewBufsLock);

    if(mPreviewing) {
        ret = BAD_VALUE;
        goto EXIT;
    }

    for (int i = 0; i < mPreviewBufferCountQueueable; i++) {

        mVideoInfo->buf.index = i;
        mVideoInfo->buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        mVideoInfo->buf.memory = V4L2_MEMORY_MMAP;

        ret = v4lIoctl(mCameraHandle, VIDIOC_QBUF, &mVideoInfo->buf);//请求分配内存
        if (ret < 0) {
            CAMHAL_LOGEA("VIDIOC_QBUF Failed");
            goto EXIT;
        }
        nQueued++;
    }

    ret = v4lStartStreaming();

    // Create and start preview thread for receiving buffers from V4L Camera
    if(!mCapturing) {
        mPreviewThread = new PreviewThread(this);//开启PreviewThread
        CAMHAL_LOGDA("Created preview thread");
    }

    //Update the flag to indicate we are previewing
    mPreviewing = true;
    mCapturing = false;

EXIT:
    LOG_FUNCTION_NAME_EXIT;
    return ret;
}

int V4LCameraAdapter::previewThread()
{
    status_t ret = NO_ERROR;
    int width, height;
    CameraFrame frame;
    void *y_uv[2];
    int index = 0;
    int stride = 4096;
    char *fp = NULL;

    mParams.getPreviewSize(&width, &height);

    if (mPreviewing) {

        fp = this->GetFrame(index);
        if(!fp) {
            ret = BAD_VALUE;
            goto EXIT;
        }
        CameraBuffer *buffer = mPreviewBufs.keyAt(index);//获取camerabuffer
        CameraFrame *lframe = (CameraFrame *)mFrameQueue.valueFor(buffer);//获取cameraframe
        if (!lframe) {
            ret = BAD_VALUE;
            goto EXIT;
        }

        debugShowFPS();

        if ( mFrameSubscribers.size() == 0 ) {
            ret = BAD_VALUE;
            goto EXIT;
        }
        y_uv[0] = (void*) lframe->mYuv[0];
        //y_uv[1] = (void*) lframe->mYuv[1];
        //y_uv[1] = (void*) (lframe->mYuv[0] + height*stride);
        convertYUV422ToNV12Tiler ( (unsigned char*)fp, (unsigned char*)y_uv[0], width, height);//convert the data
        CAMHAL_LOGVB("##...index= %d.;camera buffer= 0x%x; y= 0x%x; UV= 0x%x.",index, buffer, y_uv[0], y_uv[1] );

#ifdef SAVE_RAW_FRAMES
        unsigned char* nv12_buff = (unsigned char*) malloc(width*height*3/2);
        //Convert yuv422i to yuv420sp(NV12) & dump the frame to a file
        convertYUV422ToNV12 ( (unsigned char*)fp, nv12_buff, width, height);
        saveFile( nv12_buff, ((width*height)*3/2) );//if you want to save the data,save it
        free (nv12_buff);
#endif
        //填充frame结构，用于数据处理
        frame.mFrameType = CameraFrame::PREVIEW_FRAME_SYNC;
        frame.mBuffer = buffer;
        frame.mLength = width*height*3/2;
        frame.mAlignment = stride;
        frame.mOffset = 0;
        frame.mTimestamp = systemTime(SYSTEM_TIME_MONOTONIC);
        frame.mFrameMask = (unsigned int)CameraFrame::PREVIEW_FRAME_SYNC;

        if (mRecording)
        {
            frame.mFrameMask |= (unsigned int)CameraFrame::VIDEO_FRAME_SYNC;
            mFramesWithEncoder++;
        }

        //这里是重点，数据回调，或者使用overlay方式显示这里是决定性调用
        ret = setInitFrameRefCount(frame.mBuffer, frame.mFrameMask);
        if (ret != NO_ERROR) {
            CAMHAL_LOGDB("Error in setInitFrameRefCount %d", ret);
        } else {
            ret = sendFrameToSubscribers(&frame);
        }
    }
EXIT:

    return ret;
}

现在就开始看看setInitFrameCount方法都做了些什么

int BaseCameraAdapter::setInitFrameRefCount(CameraBuffer * buf, unsigned int mask)
{
  int ret = NO_ERROR;
  unsigned int lmask;

  LOG_FUNCTION_NAME;

  if (buf == NULL)
    {
      return -EINVAL;
    }

  for( lmask = 1; lmask < CameraFrame::ALL_FRAMES; lmask <<= 1){
    if( lmask & mask ){
      switch( lmask ){

      case CameraFrame::IMAGE_FRAME:
        {
          setFrameRefCount(buf, CameraFrame::IMAGE_FRAME, (int) mImageSubscribers.size());
        }
        break;
      case CameraFrame::RAW_FRAME:
        {
          setFrameRefCount(buf, CameraFrame::RAW_FRAME, mRawSubscribers.size());
        }
        break;
      case CameraFrame::PREVIEW_FRAME_SYNC:
        {
          setFrameRefCount(buf, CameraFrame::PREVIEW_FRAME_SYNC, mFrameSubscribers.size());//这里这个mFrameSubscribers对应的key上保存着响应的callback方法
        }
        break;
      case CameraFrame::SNAPSHOT_FRAME:
        {
          setFrameRefCount(buf, CameraFrame::SNAPSHOT_FRAME, mSnapshotSubscribers.size());
        }
        break;
      case CameraFrame::VIDEO_FRAME_SYNC:
        {
          setFrameRefCount(buf,CameraFrame::VIDEO_FRAME_SYNC, mVideoSubscribers.size());
        }
        break;
      case CameraFrame::FRAME_DATA_SYNC:
        {
          setFrameRefCount(buf, CameraFrame::FRAME_DATA_SYNC, mFrameDataSubscribers.size());
        }
        break;
      case CameraFrame::REPROCESS_INPUT_FRAME:
        {
          setFrameRefCount(buf,CameraFrame::REPROCESS_INPUT_FRAME, mVideoInSubscribers.size());
        }
        break;
      default:
        CAMHAL_LOGEB("FRAMETYPE NOT SUPPORTED 0x%x", lmask);
        break;
      }//SWITCH
      mask &= ~lmask;
    }//IF
  }//FOR
  LOG_FUNCTION_NAME_EXIT;
  return ret;
}

上面我标注的部分通过enableMsgType方法实现mFrameSubscribers.add的，经callback添加到对应的key处，算是实现关联，
同样的通过disableMsgType方法实现mFrameSubscribers.removeItem的，具体在哪里调用 enableMsgType和disableMsgType之后再给予说明

void BaseCameraAdapter::setFrameRefCount(CameraBuffer * frameBuf, CameraFrame::FrameType frameType, int refCount)
{

    LOG_FUNCTION_NAME;

    switch ( frameType )
        {
        case CameraFrame::IMAGE_FRAME:
        case CameraFrame::RAW_FRAME:
                {
                Mutex::Autolock lock(mCaptureBufferLock);
                mCaptureBuffersAvailable.replaceValueFor(frameBuf, refCount);
                }
            break;
        case CameraFrame::SNAPSHOT_FRAME:
                {
                Mutex::Autolock lock(mSnapshotBufferLock);
                mSnapshotBuffersAvailable.replaceValueFor( ( unsigned int ) frameBuf, refCount);
                }
            break;
        case CameraFrame::PREVIEW_FRAME_SYNC:
                {
                Mutex::Autolock lock(mPreviewBufferLock)
                mPreviewBuffersAvailable.replaceValueFor(frameBuf, refCount);//这里我的理解是refCount和frameBuf实现了绑定，即camerabuf保存在mPreviewBuffersAvailable对应的key处
                }
            break;
        case CameraFrame::FRAME_DATA_SYNC:
                {
                Mutex::Autolock lock(mPreviewDataBufferLock);
                mPreviewDataBuffersAvailable.replaceValueFor(frameBuf, refCount);
                }
            break;
        case CameraFrame::VIDEO_FRAME_SYNC:
                {
                Mutex::Autolock lock(mVideoBufferLock);
                mVideoBuffersAvailable.replaceValueFor(frameBuf, refCount);
                }
            break;
        case CameraFrame::REPROCESS_INPUT_FRAME: {
            Mutex::Autolock lock(mVideoInBufferLock);
            mVideoInBuffersAvailable.replaceValueFor(frameBuf, refCount);
        }
            break;
        default:
            break;
        };

    LOG_FUNCTION_NAME_EXIT;

}

接下我们看看 sendFrameToSubscribers方法的具体实现过程

status_t BaseCameraAdapter::sendFrameToSubscribers(CameraFrame *frame)
{
    status_t ret = NO_ERROR;
    unsigned int mask;

    if ( NULL == frame )
        {
        CAMHAL_LOGEA("Invalid CameraFrame");
        return -EINVAL;
        }

    for( mask = 1; mask < CameraFrame::ALL_FRAMES; mask <<= 1){
      if( mask & frame->mFrameMask ){
        switch( mask ){

        case CameraFrame::IMAGE_FRAME:
          {
#if PPM_INSTRUMENTATION || PPM_INSTRUMENTATION_ABS
            CameraHal::PPM("Shot to Jpeg: ", &mStartCapture);
#endif
            ret = __sendFrameToSubscribers(frame, &mImageSubscribers, CameraFrame::IMAGE_FRAME);
          }
          break;
        case CameraFrame::RAW_FRAME:
          {
            ret = __sendFrameToSubscribers(frame, &mRawSubscribers, CameraFrame::RAW_FRAME);
          }
          break;
        case CameraFrame::PREVIEW_FRAME_SYNC:
          {
            ret = __sendFrameToSubscribers(frame, &mFrameSubscribers, CameraFrame::PREVIEW_FRAME_SYNC);
          }
          break;
        case CameraFrame::SNAPSHOT_FRAME:
          {
            ret = __sendFrameToSubscribers(frame, &mSnapshotSubscribers, CameraFrame::SNAPSHOT_FRAME);
          }
          break;
        case CameraFrame::VIDEO_FRAME_SYNC:
          {
            ret = __sendFrameToSubscribers(frame, &mVideoSubscribers, CameraFrame::VIDEO_FRAME_SYNC);
          }
          break;
        case CameraFrame::FRAME_DATA_SYNC:
          {
            ret = __sendFrameToSubscribers(frame, &mFrameDataSubscribers, CameraFrame::FRAME_DATA_SYNC);
          }
          break;
        case CameraFrame::REPROCESS_INPUT_FRAME:
          {
            ret = __sendFrameToSubscribers(frame, &mVideoInSubscribers, CameraFrame::REPROCESS_INPUT_FRAME);
          }
          break;
        default:
          CAMHAL_LOGEB("FRAMETYPE NOT SUPPORTED 0x%x", mask);
        break;
        }//SWITCH
        frame->mFrameMask &= ~mask;

        if (ret != NO_ERROR) {
            goto EXIT;
        }
      }//IF
    }//FOR

 EXIT:
    return ret;
}

status_t BaseCameraAdapter::__sendFrameToSubscribers(CameraFrame* frame,
                                                     KeyedVector<int, frame_callback> *subscribers,
                                                     CameraFrame::FrameType frameType)
{
    size_t refCount = 0;
    status_t ret = NO_ERROR;
    frame_callback callback = NULL;

    frame->mFrameType = frameType;

    if ( (frameType == CameraFrame::PREVIEW_FRAME_SYNC) ||
         (frameType == CameraFrame::VIDEO_FRAME_SYNC) ||
         (frameType == CameraFrame::SNAPSHOT_FRAME) ){
        if (mFrameQueue.size() > 0){
          CameraFrame *lframe = (CameraFrame *)mFrameQueue.valueFor(frame->mBuffer);
          frame->mYuv[0] = lframe->mYuv[0];
          frame->mYuv[1] = frame->mYuv[0] + (frame->mLength + frame->mOffset)*2/3;
        }
        else{
          CAMHAL_LOGDA("Empty Frame Queue");
          return -EINVAL;
        }
      }

    if (NULL != subscribers) {
        refCount = getFrameRefCount(frame->mBuffer, frameType);//通过这个refCount可以找到对应的callback方法

        if (refCount == 0) {
            CAMHAL_LOGDA("Invalid ref count of 0");
            return -EINVAL;
        }

        if (refCount > subscribers->size()) {
            CAMHAL_LOGEB("Invalid ref count for frame type: 0x%x", frameType);
            return -EINVAL;
        }

        CAMHAL_LOGVB("Type of Frame: 0x%x address: 0x%x refCount start %d",
                     frame->mFrameType,
                     ( uint32_t ) frame->mBuffer,
                     refCount);

        for ( unsigned int i = 0 ; i < refCount; i++ ) {
            frame->mCookie = ( void * ) subscribers->keyAt(i);
            callback = (frame_callback) subscribers->valueAt(i);

            if (!callback) {
                CAMHAL_LOGEB("callback not set for frame type: 0x%x", frameType);
                return -EINVAL;
            }

            callback(frame);
        }
    } else {
        CAMHAL_LOGEA("Subscribers is null??");
        return -EINVAL;
    }

    return ret;
}

这里别的我们先暂且不分析，但是callback到底是从哪里来的，这个我们必须说清楚
上面在实例化displayadapter时有这样一步： 3. mDisplayAdapter - > setFrameProvider ( mCameraAdapter )//这一步是关键，之后会遇到的
我们看看setFrameProvider这个方法的实现：

int ANativeWindowDisplayAdapter::setFrameProvider(FrameNotifier *frameProvider)
{
    LOG_FUNCTION_NAME;

    // Check for NULL pointer
    if ( !frameProvider ) {
        CAMHAL_LOGEA("NULL passed for frame provider");
        LOG_FUNCTION_NAME_EXIT;
        return BAD_VALUE;
    }

    //Release any previous frame providers
    if ( NULL != mFrameProvider ) {
        delete mFrameProvider;
    }

    /** Dont do anything here, Just save the pointer for use when display is
         actually enabled or disabled
    */
    mFrameProvider = new FrameProvider(frameProvider, this, frameCallbackRelay);//实例化一个FrameProvider，这其中有一个参数非常重要：frameCallbackRelay，他的定义在下面给出

    LOG_FUNCTION_NAME_EXIT;

    return NO_ERROR;
}

void ANativeWindowDisplayAdapter::frameCallbackRelay(CameraFrame* caFrame)
{

    if ( NULL != caFrame )
        {
        if ( NULL != caFrame->mCookie )
            {
            ANativeWindowDisplayAdapter *da = (ANativeWindowDisplayAdapter*) caFrame->mCookie;
            da->frameCallback(caFrame);
        }
        else
            {
            CAMHAL_LOGEB("Invalid Cookie in Camera Frame = %p, Cookie = %p", caFrame, caFrame->mCookie);
            }
        }
    else
        {
        CAMHAL_LOGEB("Invalid Camera Frame = %p", caFrame);
    }

}

void ANativeWindowDisplayAdapter::frameCallback(CameraFrame* caFrame)
{
    ///Call queueBuffer of overlay in the context of the callback thread
    DisplayFrame df;
    df.mBuffer = caFrame->mBuffer;
    df.mType = (CameraFrame::FrameType) caFrame->mFrameType;
    df.mOffset = caFrame->mOffset;
    df.mWidthStride = caFrame->mAlignment;
    df.mLength = caFrame->mLength;
    df.mWidth = caFrame->mWidth;
    df.mHeight = caFrame->mHeight;
    PostFrame(df);
}

这个回调函数在这里设置，等待数据回调，我们很有必要去看看 FrameProvider这个类的构造函数，他是怎样让其他方法调用到这个回调函数的呢

FrameProvider(FrameNotifier *fn, void* cookie, frame_callback frameCallback)
        :mFrameNotifier(fn), mCookie(cookie),mFrameCallback(frameCallback) { }

这个构造函数还是很有意思，没有任何实现，只是通过传入的三个参数实例化了三个对象而已
1. mFrameNotifier ( fn ) ,  //这里mFrameNotifier就是camerasdapter
2.mCookie ( cookie ) ,
3. mFrameCallback ( frameCallback ) //mFrameCallback指向我们定义好的callback方法
我们接着就需要到之前已经提到过的startPreview方法中cameraPreviewInitialization的方法中去看了

////////////
/**
   @brief Set preview mode related initialization
          -> Camera Adapter set params
          -> Allocate buffers
          -> Set use buffers for preview
   @param none
   @return NO_ERROR
   @todo Update function header with the different errors that are possible

 */
status_t CameraHal::cameraPreviewInitialization()
{

    status_t ret = NO_ERROR;
    CameraAdapter::BuffersDescriptor desc;
    CameraFrame frame;
    unsigned int required_buffer_count;
    unsigned int max_queueble_buffers;

#if PPM_INSTRUMENTATION || PPM_INSTRUMENTATION_ABS
        gettimeofday(&mStartPreview, NULL);
#endif

    LOG_FUNCTION_NAME;

    if (mPreviewInitializationDone) {
        return NO_ERROR;
    }

    if ( mPreviewEnabled ){
      CAMHAL_LOGDA("Preview already running");
      LOG_FUNCTION_NAME_EXIT;
      return ALREADY_EXISTS;
    }

    if ( NULL != mCameraAdapter ) {
      ret = mCameraAdapter->setParameters(mParameters);
    }

    if ((mPreviewStartInProgress == false) && (mDisplayPaused == false)){
      ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_QUERY_RESOLUTION_PREVIEW,( int ) &frame);
      if ( NO_ERROR != ret ){
        CAMHAL_LOGEB("Error: CAMERA_QUERY_RESOLUTION_PREVIEW %d", ret);
        return ret;
      }

      ///Update the current preview width and height
      mPreviewWidth = frame.mWidth;
      mPreviewHeight = frame.mHeight;
    }

    ///If we don't have the preview callback enabled and display adapter,
    if(!mSetPreviewWindowCalled || (mDisplayAdapter.get() == NULL)){
      CAMHAL_LOGD("Preview not started. Preview in progress flag set");
      mPreviewStartInProgress = true;
      ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_SWITCH_TO_EXECUTING);
      if ( NO_ERROR != ret ){
        CAMHAL_LOGEB("Error: CAMERA_SWITCH_TO_EXECUTING %d", ret);
        return ret;
      }
      return NO_ERROR;
    }

    if( (mDisplayAdapter.get() != NULL) && ( !mPreviewEnabled ) && ( mDisplayPaused ) )
        {
        CAMHAL_LOGDA("Preview is in paused state");

        mDisplayPaused = false;
        mPreviewEnabled = true;
        if ( NO_ERROR == ret )
            {
            ret = mDisplayAdapter->pauseDisplay(mDisplayPaused);

            if ( NO_ERROR != ret )
                {
                CAMHAL_LOGEB("Display adapter resume failed %x", ret);
                }
            }
        //restart preview callbacks
        if(mMsgEnabled & CAMERA_MSG_PREVIEW_FRAME)
        {
            mAppCallbackNotifier->enableMsgType (CAMERA_MSG_PREVIEW_FRAME);
        }

        signalEndImageCapture();
        return ret;
        }

    required_buffer_count = atoi(mCameraProperties->get(CameraProperties::REQUIRED_PREVIEW_BUFS));

    ///Allocate the preview buffers
    ret = allocPreviewBufs(mPreviewWidth, mPreviewHeight, mParameters.getPreviewFormat(), required_buffer_count, max_queueble_buffers);

    if ( NO_ERROR != ret )
        {
        CAMHAL_LOGEA("Couldn't allocate buffers for Preview");
        goto error;
        }

    if ( mMeasurementEnabled )
        {

        ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_QUERY_BUFFER_SIZE_PREVIEW_DATA,
                                          ( int ) &frame,
                                          required_buffer_count);
        if ( NO_ERROR != ret )
            {
            return ret;
            }

         ///Allocate the preview data buffers
        ret = allocPreviewDataBufs(frame.mLength, required_buffer_count);
        if ( NO_ERROR != ret ) {
            CAMHAL_LOGEA("Couldn't allocate preview data buffers");
            goto error;
           }

        if ( NO_ERROR == ret )
            {
            desc.mBuffers = mPreviewDataBuffers;
            desc.mOffsets = mPreviewDataOffsets;
            desc.mFd = mPreviewDataFd;
            desc.mLength = mPreviewDataLength;
            desc.mCount = ( size_t ) required_buffer_count;
            desc.mMaxQueueable = (size_t) required_buffer_count;

            mCameraAdapter->sendCommand(CameraAdapter::CAMERA_USE_BUFFERS_PREVIEW_DATA,
                                        ( int ) &desc);
            }

        }

    ///Pass the buffers to Camera Adapter
    desc.mBuffers = mPreviewBuffers;
    desc.mOffsets = mPreviewOffsets;
    desc.mFd = mPreviewFd;
    desc.mLength = mPreviewLength;
    desc.mCount = ( size_t ) required_buffer_count;
    desc.mMaxQueueable = (size_t) max_queueble_buffers;

    ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_USE_BUFFERS_PREVIEW,
                                      ( int ) &desc);

    if ( NO_ERROR != ret )
        {
        CAMHAL_LOGEB("Failed to register preview buffers: 0x%x", ret);
        freePreviewBufs();
        return ret;
        }

    mAppCallbackNotifier->startPreviewCallbacks(mParameters, mPreviewBuffers, mPreviewOffsets, mPreviewFd, mPreviewLength, required_buffer_count);

    ///Start the callback notifier
    ret = mAppCallbackNotifier->start();

    if( ALREADY_EXISTS == ret )
        {
        //Already running, do nothing
        CAMHAL_LOGDA("AppCallbackNotifier already running");
        ret = NO_ERROR;
        }
    else if ( NO_ERROR == ret ) {
        CAMHAL_LOGDA("Started AppCallbackNotifier..");
        mAppCallbackNotifier->setMeasurements(mMeasurementEnabled);
        }
    else
        {
        CAMHAL_LOGDA("Couldn't start AppCallbackNotifier");
        goto error;
        }

    if (ret == NO_ERROR) mPreviewInitializationDone = true;
    return ret;

    error:

        CAMHAL_LOGEA("Performing cleanup after error");

        //Do all the cleanup
        freePreviewBufs();
        mCameraAdapter->sendCommand(CameraAdapter::CAMERA_STOP_PREVIEW);
        if(mDisplayAdapter.get() != NULL)
            {
            mDisplayAdapter->disableDisplay(false);
            }
        mAppCallbackNotifier->stop();
        mPreviewStartInProgress = false;
        mPreviewEnabled = false;
        LOG_FUNCTION_NAME_EXIT;

        return ret;
}

我们就看看这个方法的是实现吧：mAppCallbackNotifier - > enableMsgType  ( CAMERA_MSG_PREVIEW_FRAME ) ;

status_t AppCallbackNotifier::enableMsgType(int32_t msgType)
{
    if( msgType & CAMERA_MSG_PREVIEW_FRAME ) {
        mFrameProvider->enableFrameNotification(CameraFrame::PREVIEW_FRAME_SYNC);
    }

    if( msgType & CAMERA_MSG_POSTVIEW_FRAME ) {
        mFrameProvider->enableFrameNotification(CameraFrame::SNAPSHOT_FRAME);
    }

    if(msgType & CAMERA_MSG_RAW_IMAGE) {
        mFrameProvider->enableFrameNotification(CameraFrame::RAW_FRAME);
    }

    return NO_ERROR;
}

int FrameProvider::enableFrameNotification(int32_t frameTypes)
{
    LOG_FUNCTION_NAME;
    status_t ret = NO_ERROR;

    ///Enable the frame notification to CameraAdapter (which implements FrameNotifier interface)
    mFrameNotifier->enableMsgType(frameTypes<<MessageNotifier::FRAME_BIT_FIELD_POSITION, mFrameCallback, NULL, mCookie);

    LOG_FUNCTION_NAME_EXIT;
    return ret;
}

这里这个 enableMsgType其实就是前面已经提到过的那个 enableMsgType方法，实现callback方法add到响应的key上
这里这个mFrameNotifier是FrameNotifier的对象，FrameNotifier这个类继承于MessageNotifier
而BaseCameraAdapter继承于CameraAdapter，CameraAdapter又继承于FrameNotifier，所以 mFrameNotifier对象调用的 enableMsgType方法其实是一个虚函数，
最终调用的是 BaseCameraAdapter这个类中定义的 enableMsgType 方法，我们来看一看他的实现：

void BaseCameraAdapter::enableMsgType(int32_t msgs, frame_callback callback, event_callback eventCb, void* cookie)
{
    Mutex::Autolock lock(mSubscriberLock);

    LOG_FUNCTION_NAME;

    int32_t frameMsg = ((msgs >> MessageNotifier::FRAME_BIT_FIELD_POSITION) & EVENT_MASK);
    int32_t eventMsg = ((msgs >> MessageNotifier::EVENT_BIT_FIELD_POSITION) & EVENT_MASK);

    if ( frameMsg != 0 )
        {
        CAMHAL_LOGVB("Frame message type id=0x%x subscription request", frameMsg);
        switch ( frameMsg )
            {
            case CameraFrame::PREVIEW_FRAME_SYNC:
                mFrameSubscribers.add((int) cookie, callback);
                break;
            case CameraFrame::FRAME_DATA_SYNC:
                mFrameDataSubscribers.add((int) cookie, callback);
                break;
            case CameraFrame::SNAPSHOT_FRAME:
                mSnapshotSubscribers.add((int) cookie, callback);
                break;
            case CameraFrame::IMAGE_FRAME:
                mImageSubscribers.add((int) cookie, callback);
                break;
            case CameraFrame::RAW_FRAME:
                mRawSubscribers.add((int) cookie, callback);
                break;
            case CameraFrame::VIDEO_FRAME_SYNC:
                mVideoSubscribers.add((int) cookie, callback);
                break;
            case CameraFrame::REPROCESS_INPUT_FRAME:
                mVideoInSubscribers.add((int) cookie, callback);
                break;
            default:
                CAMHAL_LOGEA("Frame message type id=0x%x subscription no supported yet!", frameMsg);
                break;
            }
        }

    if ( eventMsg != 0)
        {
        CAMHAL_LOGVB("Event message type id=0x%x subscription request", eventMsg);
        if ( CameraHalEvent::ALL_EVENTS == eventMsg )
            {
            mFocusSubscribers.add((int) cookie, eventCb);
            mShutterSubscribers.add((int) cookie, eventCb);
            mZoomSubscribers.add((int) cookie, eventCb);
            mMetadataSubscribers.add((int) cookie, eventCb);
            }
        else
            {
            CAMHAL_LOGEA("Event message type id=0x%x subscription no supported yet!", eventMsg);
            }
        }

    LOG_FUNCTION_NAME_EXIT;
}

这里通过 mFrameSubscribers . add ( ( int )  cookie ,  callback )这个方法将 mFrameCallback回调函数与key相关联
所以上面可以通过 callback  =   ( frame_callback )  subscribers - > valueAt ( i ) ;
这个方法获取callback的实现，因为上面已经实现了关联，所以数据最终是通过上面分析道的方法继续进行数据流显示

void ANativeWindowDisplayAdapter::frameCallback(CameraFrame* caFrame)
{
    ///Call queueBuffer of overlay in the context of the callback thread
    DisplayFrame df;
    df.mBuffer = caFrame->mBuffer;
    df.mType = (CameraFrame::FrameType) caFrame->mFrameType;
    df.mOffset = caFrame->mOffset;
    df.mWidthStride = caFrame->mAlignment;
    df.mLength = caFrame->mLength;
    df.mWidth = caFrame->mWidth;
    df.mHeight = caFrame->mHeight;
    PostFrame(df);//这里填充了DisplayFrame这个结构，并调用PostFrome实现显示
}

这里PostFrame成了我要研究的主要内容，将数据以DisplayFrame结构的方式打包之后到底是怎么实现显示的呢？？

status_t ANativeWindowDisplayAdapter::PostFrame(ANativeWindowDisplayAdapter::DisplayFrame &dispFrame)
{
    status_t ret = NO_ERROR;
    uint32_t actualFramesWithDisplay = 0;
    android_native_buffer_t *buffer = NULL;
    GraphicBufferMapper &mapper = GraphicBufferMapper::get();
    int i;

    ///@todo Do cropping based on the stabilized frame coordinates
    ///@todo Insert logic to drop frames here based on refresh rate of
    ///display or rendering rate whichever is lower
    ///Queue the buffer to overlay

    if ( NULL == mANativeWindow ) {
        return NO_INIT;
    }

    if (!mBuffers || !dispFrame.mBuffer) {
        CAMHAL_LOGEA("NULL sent to PostFrame");
        return BAD_VALUE;
    }

    for ( i = 0; i < mBufferCount; i++ )
        {
        if ( dispFrame.mBuffer == &mBuffers[i] )
            {
            break;
        }
    }


    mFramesType.add( (int)mBuffers[i].opaque ,dispFrame.mType );

    if ( mDisplayState == ANativeWindowDisplayAdapter::DISPLAY_STARTED &&
                (!mPaused || CameraFrame::CameraFrame::SNAPSHOT_FRAME == dispFrame.mType) &&
                !mSuspend)
    {
        Mutex::Autolock lock(mLock);
        uint32_t xOff = (dispFrame.mOffset% PAGE_SIZE);
        uint32_t yOff = (dispFrame.mOffset / PAGE_SIZE);

        // Set crop only if current x and y offsets do not match with frame offsets
        if((mXOff!=xOff) || (mYOff!=yOff))
        {
            CAMHAL_LOGDB("Offset %d xOff = %d, yOff = %d", dispFrame.mOffset, xOff, yOff);
            uint8_t bytesPerPixel;
            ///Calculate bytes per pixel based on the pixel format
            if(strcmp(mPixelFormat, (const char *) CameraParameters::PIXEL_FORMAT_YUV422I) == 0)
                {
                bytesPerPixel = 2;
                }
            else if(strcmp(mPixelFormat, (const char *) CameraParameters::PIXEL_FORMAT_RGB565) == 0)
                {
                bytesPerPixel = 2;
                }
            else if(strcmp(mPixelFormat, (const char *) CameraParameters::PIXEL_FORMAT_YUV420SP) == 0)
                {
                bytesPerPixel = 1;
                }
            else
                {
                bytesPerPixel = 1;
            }

            CAMHAL_LOGVB(" crop.left = %d crop.top = %d crop.right = %d crop.bottom = %d",
                          xOff/bytesPerPixel, yOff , (xOff/bytesPerPixel)+mPreviewWidth, yOff+mPreviewHeight);
            // We'll ignore any errors here, if the surface is
            // already invalid, we'll know soon enough.
            mANativeWindow->set_crop(mANativeWindow, xOff/bytesPerPixel, yOff,
                                     (xOff/bytesPerPixel)+mPreviewWidth, yOff+mPreviewHeight);

            ///Update the current x and y offsets
            mXOff = xOff;
            mYOff = yOff;
        }

        {
            buffer_handle_t *handle = (buffer_handle_t *) mBuffers[i].opaque;
            // unlock buffer before sending to display
            mapper.unlock(*handle);
            ret = mANativeWindow->enqueue_buffer(mANativeWindow, handle);
        }
        if ( NO_ERROR != ret ) {
            CAMHAL_LOGE("Surface::queueBuffer returned error %d", ret);
        }

        mFramesWithCameraAdapterMap.removeItem((buffer_handle_t *) dispFrame.mBuffer->opaque);


        // HWComposer has not minimum buffer requirement. We should be able to dequeue
        // the buffer immediately
        TIUTILS::Message msg;
        mDisplayQ.put(&msg);


#if PPM_INSTRUMENTATION || PPM_INSTRUMENTATION_ABS

        if ( mMeasureStandby )
            {
            CameraHal::PPM("Standby to first shot: Sensor Change completed - ", &mStandbyToShot);
            mMeasureStandby = false;
            }
        else if (CameraFrame::CameraFrame::SNAPSHOT_FRAME == dispFrame.mType)
            {
            CameraHal::PPM("Shot to snapshot: ", &mStartCapture);
            mShotToShot = true;
            }
        else if ( mShotToShot )
            {
            CameraHal::PPM("Shot to shot: ", &mStartCapture);
            mShotToShot = false;
        }
#endif

    }
    else
    {
        Mutex::Autolock lock(mLock);
        buffer_handle_t *handle = (buffer_handle_t *) mBuffers[i].opaque;

        // unlock buffer before giving it up
        mapper.unlock(*handle);

        // cancel buffer and dequeue another one
        ret = mANativeWindow->cancel_buffer(mANativeWindow, handle);
        if ( NO_ERROR != ret ) {
            CAMHAL_LOGE("Surface::cancelBuffer returned error %d", ret);
        }

        mFramesWithCameraAdapterMap.removeItem((buffer_handle_t *) dispFrame.mBuffer->opaque);

        TIUTILS::Message msg;
        mDisplayQ.put(&msg);
        ret = NO_ERROR;
    }

    return ret;
}

这个显示的过程相对来说还是比较复杂的，之后还需要花点时间研究一下

待续。。。。。