Android之Camera拍照

一、看看调用时序图

1.拍照命令时序图

2.拍照数据回调时序图

二、看看源码分析

hardware/amlogic/camera/CameraHal.cpp

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1. status_t CameraHal::takePicture( ){  
2.   ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_START_IMAGE_CAPTURE,  (int) &mStartCapture);  
3. }  

调用父类方法：

hardware/amlogic/camera/BaseCameraAdapter.cpp

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1. status_t BaseCameraAdapter::sendCommand(CameraCommands operation, int value1, int value2, int value3){  
2.   switch ( operation ) {  
3.     case CameraAdapter::CAMERA_START_IMAGE_CAPTURE:  
4.       ret = takePicture();  
5.   }  
6. }  

调用子类方法：

hardware/amlogic/camera/V4LCameraAdapter/V4LCameraAdapter.cpp

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1. status_t V4LCameraAdapter::takePicture(){  
2.   if (createThread(beginPictureThread, this) == false)  
3.     return -1;  
4. }  
5. /*static*/ int V4LCameraAdapter::beginPictureThread(void *cookie){  
6.   V4LCameraAdapter *c = (V4LCameraAdapter *)cookie;  
7.   return c->pictureThread();  
8. }  
9. int V4LCameraAdapter::pictureThread(){  
10.   ret = sendFrameToSubscribers(&frame);  
11. }  

调用父类方法：

hardware/amlogic/camera/BaseCameraAdapter.cpp

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1. status_t BaseCameraAdapter::sendFrameToSubscribers(CameraFrame *frame){  
2.   ret = __sendFrameToSubscribers(frame, &mImageSubscribers, CameraFrame::IMAGE_FRAME);  
3. /* 
4. //如上callback的设置 
5. hardware/amlogic/camera/CameraHal.cpp 
6. status_t CameraHal::initialize(CameraProperties::Properties* properties){ 
7.   mAppCallbackNotifier->setEventProvider(eventMask, mCameraAdapter); 
8.   mAppCallbackNotifier->setFrameProvider(mCameraAdapter); 
9. } 
10.  
11. hardware/amlogic/camera/AppCallbackNotifier.cpp  
12. void AppCallbackNotifier::setFrameProvider(FrameNotifier *frameNotifier){ 
13.   mFrameProvider = new FrameProvider(frameNotifier, this, frameCallbackRelay); 
14.   mFrameProvider->enableFrameNotification(CameraFrame::IMAGE_FRAME); 
15.   mFrameProvider->enableFrameNotification(CameraFrame::RAW_FRAME); 
16. } 
17.  
18. hardware/amlogic/camera/inc/CamerHal.h  
19. class FrameProvider{ 
20.   public: 
21.     FrameProvider(FrameNotifier *fn, void* cookie, frame_callback frameCallback) 
22.                   :mFrameNotifier(fn), mCookie(cookie),mFrameCallback(frameCallback) { } 
23. } 
24. hardware/amlogic/camera/CameraHalUtilClasses.cpp 
25. int FrameProvider::enableFrameNotification(int32_t frameTypes){ 
26.   mFrameNotifier->enableMsgType(frameTypes<<MessageNotifier::FRAME_BIT_FIELD_POSITION 
27.                                 , mFrameCallback 
28.                                 , NULL 
29.                                 , mCookie); 
30. } 
31. hardware/amlogic/camera/BaseCameraAdapter.cpp 
32. void BaseCameraAdapter::enableMsgType(int32_t msgs, frame_callback callback, event_callback eventCb, void* cookie){ 
33.   if ( CameraFrame::PREVIEW_FRAME_SYNC == msgs ){ 
34.     mFrameSubscribers.add((int) cookie, callback); 
35.   } 
36.   else if ( CameraFrame::IMAGE_FRAME == msgs){ 
37.     mImageSubscribers.add((int) cookie, callback); 
38.   } 
39.   else if ( CameraFrame::RAW_FRAME == msgs){ 
40.     mRawSubscribers.add((int) cookie, callback); 
41.   } 
42. } 
43. //以下callback就是frameCallbackRelay 
44. //callbak-》subscribers-》mImageSubscribers-》mImageSubscribers.add((int) cookie, callback)-》mFrameCallback-》frameCallbackRelay 
45. */  
46. }  
47. status_t BaseCameraAdapter::__sendFrameToSubscribers(CameraFrame* frame,  
48.      KeyedVector<int, frame_callback> *subscribers,  
49.      CameraFrame::FrameType frameType){  
50.   callback = (frame_callback) subscribers->valueAt(k);  
51.   callback(frame);  
52. }  

该回调函数即是：

hardware/amlogic/camera/AppCallbackNotifier.cpp

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1. void AppCallbackNotifier::frameCallbackRelay(CameraFrame* caFrame){  
2.   appcbn->frameCallback(caFrame);  
3. }  
4. void AppCallbackNotifier::frameCallback(CameraFrame* caFrame){  
5.   msg.command = AppCallbackNotifier::NOTIFIER_CMD_PROCESS_FRAME;  
6.   msg.arg1 = frame;  
7.   mFrameQ.put(&msg);  
8. }  
9. void AppCallbackNotifier::notifyFrame(){  
10.   mFrameQ.get(&msg);  
11.   sp<Encoder_libjpeg> encoder = new Encoder_libjpeg(main_jpeg, tn_jpeg,  
12.     AppCallbackNotifierEncoderCallback,  
13.     (CameraFrame::FrameType)frame->mFrameType,  
14.     this,raw_picture,exif_data);  
15. }  

补充——拍照是声音的回调如下：

frameworks/av/services/camera/libcameraservice/CameraClient.cpp

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1. void CameraClient::handleShutter(void) {  
2.   mCameraService->playSound(CameraService::SOUND_SHUTTER);  
3. }  

frameworks/av/services/camera/libcameraservice/CameraService.cpp

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1. //mSoundPlayer[SOUND_SHUTTER] = newMediaPlayer("/system/media/audio/ui/camera_click.ogg");  
2. void CameraService::playSound(sound_kind kind) {  
3.   
4.   
5. }  

源码中位置：

frameworks/base/data/sounds/OriginalAudio.mk

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1. $(LOCAL_PATH)/effects/camera_click.ogg:system/media/audio/ui/camera_click.ogg  

frameworks/base/data/sounds/effects/camera_click.ogg

三、项目问题

拍照后，应用程序不调用startPreview导致预览界面不再刷新：

1.看看预览部分CameraHAL的处理

hardware/amlogic/camera/V4LCameraAdapter/V4LCameraAdapter.cpp

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1. int V4LCameraAdapter::previewThread(){  
2.   frame.mFrameMask |= CameraFrame::PREVIEW_FRAME_SYNC;  
3.   ret = sendFrameToSubscribers(&frame);  
4. }  

hardware/amlogic/camera/BaseCameraAdapter.cpp

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1. status_t BaseCameraAdapter::sendFrameToSubscribers(CameraFrame *frame){  
2.   ret = __sendFrameToSubscribers(frame, &mFrameSubscribers, CameraFrame::PREVIEW_FRAME_SYNC);  
3. }  
4. status_t BaseCameraAdapter::__sendFrameToSubscribers(CameraFrame* frame,  
5.                                                       KeyedVector<int, frame_callback> *subscribers,  
6.                                                       CameraFrame::FrameType frameType){  
7.   while(k<subscribers->size()){  
8.     callback = (frame_callback) subscribers->valueAt(k);  
9.     for(uint32_t i = 0; i<subscribers_ref.size();i++){  
10.       if((frame->mCookie == ( void * ) subscribers_ref.keyAt(i))&&(subscribers_ref.valueAt(i) == 0)){  
11.       subscribers_ref.replaceValueFor((uint32_t)frame->mCookie,1);  
12.       //CAMHAL_LOGDB("Frame callbback is available, cookie:0x%x, callback:0x%x",(uint32_t)frame->mCookie,(uint32_t)callback);  
13.       callback(frame);  
14.       k = 0;  
15.       is_find = true;  
16.       break;  
17.     }  
18.   }  
19. }  
20. /* 
21. //如上callback的设置 
22. hardware/amlogic/camera/CameraHal.cpp 
23. //设置APP回调函数 
24. status_t CameraHal::initialize(CameraProperties::Properties* properties){ 
25.   mAppCallbackNotifier->setEventProvider(eventMask, mCameraAdapter); 
26.   mAppCallbackNotifier->setFrameProvider(mCameraAdapter); 
27. } 
28. //设置刷屏回调函数 
29. status_t CameraHal::setPreviewWindow(struct preview_stream_ops *window){ 
30.   mDisplayAdapter->setFrameProvider(mCameraAdapter); 
31.   mDisplayAdapter->setErrorHandler(mAppCallbackNotifier.get()); 
32.   ret  = mDisplayAdapter->setPreviewWindow(window); 
33. } 
34. status_t CameraHal::startPreview(){ 
35.   ret = mDisplayAdapter->enableDisplay(width, height, NULL, isS3d ? &s3dParams : NULL); 
36. } 
37.  
38. //设置APP回调函数 
39. hardware/amlogic/camera/AppCallbackNotifier.cpp  
40. void AppCallbackNotifier::setFrameProvider(FrameNotifier *frameNotifier){ 
41.   mFrameProvider = new FrameProvider(frameNotifier, this, frameCallbackRelay); 
42.   mFrameProvider->enableFrameNotification(CameraFrame::IMAGE_FRAME); 
43.   mFrameProvider->enableFrameNotification(CameraFrame::RAW_FRAME); 
44. } 
45.  
46. //设置刷屏回调函数 
47. hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp 
48. int ANativeWindowDisplayAdapter::setFrameProvider(FrameNotifier *frameProvider){ 
49.   mFrameProvider = new FrameProvider(frameProvider, this, frameCallbackRelay); 
50. } 
51. int ANativeWindowDisplayAdapter::enableDisplay(int width, int height, struct timeval *refTime, S3DParameters *s3dParams){ 
52.   mFrameProvider->enableFrameNotification(CameraFrame::PREVIEW_FRAME_SYNC); 
53. } 
54.  
55. //最终设置地方 
56. hardware/amlogic/camera/inc/CamerHal.h  
57. class FrameProvider{ 
58.   public: 
59.     FrameProvider(FrameNotifier *fn, void* cookie, frame_callback frameCallback) 
60.                   :mFrameNotifier(fn), mCookie(cookie),mFrameCallback(frameCallback) { } 
61. } 
62. hardware/amlogic/camera/CameraHalUtilClasses.cpp 
63. int FrameProvider::enableFrameNotification(int32_t frameTypes){ 
64.   mFrameNotifier->enableMsgType(frameTypes<<MessageNotifier::FRAME_BIT_FIELD_POSITION 
65.                                 , mFrameCallback 
66.                                 , NULL 
67.                                 , mCookie); 
68. } 
69. hardware/amlogic/camera/BaseCameraAdapter.cpp 
70. void BaseCameraAdapter::enableMsgType(int32_t msgs, frame_callback callback, event_callback eventCb, void* cookie){ 
71.   if ( CameraFrame::PREVIEW_FRAME_SYNC == msgs ){ 
72.     mFrameSubscribers.add((int) cookie, callback); 
73.   } 
74.   else if ( CameraFrame::IMAGE_FRAME == msgs){ 
75.     mImageSubscribers.add((int) cookie, callback); 
76.   } 
77.   else if ( CameraFrame::RAW_FRAME == msgs){ 
78.     mRawSubscribers.add((int) cookie, callback); 
79. } 
80. } 
81. */  

如上callback即是ANativeWindowDisplayAdapter.cpp/AppCallbackNotifier.cpp中的frameCallbackRelay，我们分析预览画面只需要关心ANativeWindowDisplayAdapter.cpp（AppCallbackNotifier.cpp是例如拍照和录像，需要将数据送给APP）：

hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp

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1. void ANativeWindowDisplayAdapter::frameCallbackRelay(CameraFrame* caFrame){  
2.   da->frameCallback(caFrame);  
3. }  
4. void ANativeWindowDisplayAdapter::frameCallback(CameraFrame* caFrame){  
5.   PostFrame(df);  
6. }  
7. status_t ANativeWindowDisplayAdapter::PostFrame(ANativeWindowDisplayAdapter::DisplayFrame &dispFrame){  
8.   LOGD("TK----->>>>mPaused is %d\n",mPaused);//add by tankai  
9.   if ( mDisplayState == ANativeWindowDisplayAdapter::DISPLAY_STARTED &&  
10.                 (!mPaused ||  CameraFrame::CameraFrame::SNAPSHOT_FRAME == dispFrame.mType) &&  
11.                 !mSuspend){  
12.     ret = mANativeWindow->enqueue_buffer(mANativeWindow, mBufferHandleMap[i]);  
13.     mFramesWithCameraAdapterMap.removeItem((int) dispFrame.mBuffer);  
14.   }  
15.   else{  
16.     ret = mANativeWindow->cancel_buffer(mANativeWindow, mBufferHandleMap[i]);  
17.     mFramesWithCameraAdapterMap.removeItem((int) dispFrame.mBuffer);  
18.   }  
19. }  

2.问题分析

从如上可以看出：mPaused为true表示暂停刷屏，mPaused为false表示开始刷屏；我们的问题就出在这里。

hardware/camera/CameraHal.cpp

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1. status_t CameraHal::startPreview(){  
2.   if( (mDisplayAdapter.get() != NULL) && ( !mPreviewEnabled ) && ( mDisplayPaused ) ){  
3.     CAMHAL_LOGDA("Preview is in paused state");  
4.     mDisplayPaused = false;  
5.     mPreviewEnabled = true;  
6.     if ( NO_ERROR == ret ){  
7.       ret = mDisplayAdapter->pauseDisplay(mDisplayPaused); //重新开始预览  
8. /* 
9. hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp 
10. status_t ANativeWindowDisplayAdapter::pauseDisplay(bool pause){ 
11.   mPaused = pause; 
12. } 
13. */  
14.       if ( NO_ERROR != ret ){  
15.         CAMHAL_LOGEB("Display adapter resume failed %x", ret);  
16.       }  
17.     }  
18.     //restart preview callbacks  
19.     if(mMsgEnabled & CAMERA_MSG_PREVIEW_FRAME){  
20.       mAppCallbackNotifier->enableMsgType (CAMERA_MSG_PREVIEW_FRAME);  
21.     }  
22.     return ret;  
23.   }  
24. }  
25. //拍照时将mPaused置为false，暂停刷屏：  
26. status_t CameraHal::takePicture( ){  
27.   if (NO_ERROR == ret &&  
28.     NULL != mDisplayAdapter.get() && burst < 1) {  
29.     if (mCameraAdapter->getState() != CameraAdapter::VIDEO_STATE) {  
30.       mDisplayPaused = true;  
31.       mPreviewEnabled = false;  
32.       ret = mDisplayAdapter->pauseDisplay(mDisplayPaused); //暂停预览  
33. /* 
34. hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp 
35. status_t ANativeWindowDisplayAdapter::pauseDisplay(bool pause){ 
36.   mPaused = pause; 
37. } 
38. */  
39.       // since preview is paused we should stop sending preview frames too  
40.       if(mMsgEnabled & CAMERA_MSG_PREVIEW_FRAME) {  
41.         mAppCallbackNotifier->disableMsgType (mMsgEnabled & CAMERA_MSG_POSTVIEW_FRAME);  
42.         CAMHAL_LOGDA("disable MSG_PREVIEW_FRAME");  
43.       }  
44.     }  
45.   
46. #if PPM_INSTRUMENTATION || PPM_INSTRUMENTATION_ABS  
47.      mDisplayAdapter->setSnapshotTimeRef(&mStartCapture);  
48. #endif  
49.   }  
50.   
51. }  

3.问题解决

应用层在take_picture之后主动调用startpreview将mPaused改为false；

如果不需要应用主动调用，则需要在HAL将startpreview设为false。

4.如何在应用层取消掉拍照的回调

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1. camera.takePicture(shutterCallback, rawCallback, jpegCallback);  
2. 改为  
3. camera.takePicture(null, null, jpegCallback);  

原理如下：

frameworks/base/core/Java/Android/hardware/Camera.java

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1. public final void takePicture(ShutterCallback shutter, PictureCallback raw,  
2.             PictureCallback postview, PictureCallback jpeg) {  
3.         mShutterCallback = shutter;  
4.         mRawImageCallback = raw;  
5.         mPostviewCallback = postview;  
6.         mJpegCallback = jpeg;  
7.   
8.         // If callback is not set, do not send me callbacks.  
9.         int msgType = 0;  
10.         if (mShutterCallback != null) {  
11.             msgType |= CAMERA_MSG_SHUTTER;  
12.         }  
13.         if (mRawImageCallback != null) {  
14.             msgType |= CAMERA_MSG_RAW_IMAGE;  
15.         }  
16.         if (mPostviewCallback != null) {  
17.             msgType |= CAMERA_MSG_POSTVIEW_FRAME;  
18.         }  
19.         if (mJpegCallback != null) {  
20.             msgType |= CAMERA_MSG_COMPRESSED_IMAGE;  
21.         }  
22.   
23.         native_takePicture(msgType);  
24.         mFaceDetectionRunning = false;  
25.     }