最近一段时间在学习Camera2，记录一下。
demo很简单，CameraActivity中加入了一个fragment，AutoFitTextureView提供了一个方法用来设置textureView的宽高，而我们主要要分析Camera2BasicFragment的预览拍照流程
1.进入相机，获取TextureView对象，然后开启一个后台线程处理相机数据
2.判断TextureView是否有效，有效就直接openCamera()，无效就加入一个监听SufaceTextureListener，通过回调确保surfaceTexture有效，然后同样openCamera()。
3.设置相机特性--setUpCameraOutputs()，设置图片存储监听OnImageAvaliableListener，拍照图片有效会通知ImageSaver线程保存图片，设置AE，AF等
4.设置矩阵变换 configureTransform()
5.获取CameraManager对象，然后真正打开相机
manager.openCamera(mCameraId, mStateCallback, mBackgroundHandler);
其中mStateCallBack是相机状态回调。
6.打开相机成功的话，获取CameraDevice，然后创建会话--createCameraPreviewSession()，
通过mTextureView获取SurfaceTexture，通过SurafceTexture获得Surface对象，在CaptureRequest.Builder中添加Surface
然后创建会话，获得CaptureRequest对象，通过CaptureRequest发送重复请求捕捉画面，开启预览。
7.拍照流程:首先有个入口，拍照按钮点击事件，触发takePicture(),takePicture中实现了lockFocus()锁住焦点。
8.lockFocus()：设置了一个等待锁定的状态，发送一次请求，加入了一个回调CaptureCallback，这一步还没有进行拍照。
9.在CaptureCallback的process()中，状态切换为STATE_WAITING_LOCK，进行拍照，当然不一定就是该状态下进行拍照，还要对AE，AF的状态进行判断，最后不管哪个状态下，都会调用captureStillPicture()进行拍照。
10.captureStillPicture() 设置拍照捕捉请求，设置成像方向与预览方向一致，中断停止预览的重复请求，最终进行拍照，拍照数据会由imageSaver处理，保存到文件，然后通过CameraCaptureSession.CaptureCallback回调解除锁定，回复预览界面
@Override
public void onViewCreated(final View view, Bundle savedInstanceState) {
view.findViewById(R.id.picture).setOnClickListener(this);
view.findViewById(R.id.info).setOnClickListener(this);
mTextureView = (AutoFitTextureView) view.findViewById(R.id.texture);//获取mTextureView
}
...
@Override
public void onResume() {
super.onResume();
startBackgroundThread();//为相机开启了一个后台线程，这个进程用于后台执行相关的工作
if (mTextureView.isAvailable()) {//mTextureView已经创建，SurfaceTexture已经有效，则直接openCamera，用于屏幕熄灭等情况，这时onSurfaceTextureAvailable不会回调。
openCamera(mTextureView.getWidth(), mTextureView.getHeight());
} else {//SurfaceTexture处于无效状态中，则通过SurfaceTextureListener确保surface准备好。
mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);//设置mTextureView回调
}
}
...
private final TextureView.SurfaceTextureListener mSurfaceTextureListener
= new TextureView.SurfaceTextureListener() {//TextureView回调
@Override
public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {
openCamera(width, height);//SurfaceTexture有效即可openCamera,宽高是控件宽高
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture texture, int width, int height) {
configureTransform(width, height);//配置transformation，主要是矩阵旋转相关
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
return true;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture texture) {
}
};
...
private void setUpCameraOutputs(int width, int height) {包括对相机设备的选择，ImageReader的初始化和参数、回调设置。设置显示的转化矩阵，即将预览的图片调整至显示图层的大小。
Activity activity = getActivity();
CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
try {
for (String cameraId : manager.getCameraIdList()) {//获取摄像头可用列表
CameraCharacteristics characteristics
= manager.getCameraCharacteristics(cameraId);获取相机的特性
// We don't use a front facing camera in this sample.
Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);// 不使用前置摄像头
if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {
continue;
}
StreamConfigurationMap map = characteristics.get(
CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
if (map == null) {
continue;
}
// For still image captures, we use the largest available size.
Size largest = Collections.max(
Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
new CompareSizesByArea());
mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),//相机拍照图像尺寸
ImageFormat.JPEG, /*maxImages*/2);//设置ImageReader接收的图片格式，以及允许接收的最大图片数目
mImageReader.setOnImageAvailableListener(
mOnImageAvailableListener, mBackgroundHandler);//设置图片存储的监听，但在创建会话，调用capture后才能有数据
// Find out if we need to swap dimension to get the preview size relative to sensor
// coordinate.
int displayRotation = activity.getWindowManager().getDefaultDisplay().getRotation();//获取显示方向
//noinspection ConstantConditions
mSensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);//获取sensor方向
boolean swappedDimensions = false;
switch (displayRotation) {
case Surface.ROTATION_0:
case Surface.ROTATION_180:
if (mSensorOrientation == 90 || mSensorOrientation == 270) {
swappedDimensions = true;
}
break;
case Surface.ROTATION_90:
case Surface.ROTATION_270:
if (mSensorOrientation == 0 || mSensorOrientation == 180) {
swappedDimensions = true;
}
break;
default:
Log.e(TAG, "Display rotation is invalid: " + displayRotation);
}
Point displaySize = new Point();
activity.getWindowManager().getDefaultDisplay().getSize(displaySize);
int rotatedPreviewWidth = width;
int rotatedPreviewHeight = height;
int maxPreviewWidth = displaySize.x;
int maxPreviewHeight = displaySize.y;
if (swappedDimensions) {//横竖屏交换尺寸
rotatedPreviewWidth = height;
rotatedPreviewHeight = width;
maxPreviewWidth = displaySize.y;
maxPreviewHeight = displaySize.x;
}
if (maxPreviewWidth > MAX_PREVIEW_WIDTH) {
maxPreviewWidth = MAX_PREVIEW_WIDTH;
}
if (maxPreviewHeight > MAX_PREVIEW_HEIGHT) {
maxPreviewHeight = MAX_PREVIEW_HEIGHT;
}
// Danger, W.R.! Attempting to use too large a preview size could exceed the camera
// bus' bandwidth limitation, resulting in gorgeous previews but the storage of
// garbage capture data.
mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
rotatedPreviewWidth, rotatedPreviewHeight, maxPreviewWidth,
maxPreviewHeight, largest);//获取最优的预览分辨率
// We fit the aspect ratio of TextureView to the size of preview we picked.
int orientation = getResources().getConfiguration().orientation;
if (orientation == Configuration.ORIENTATION_LANDSCAPE) {
mTextureView.setAspectRatio(
mPreviewSize.getWidth(), mPreviewSize.getHeight());
//设置TextureView预览分辨率。
} else {
mTextureView.setAspectRatio(
mPreviewSize.getHeight(), mPreviewSize.getWidth());
}
// Check if the flash is supported.
//设置闪光灯
Boolean available = characteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);
mFlashSupported = available == null ? false : available;
mCameraId = cameraId;//获取当前ID
return;
}
} catch (CameraAccessException e) {
e.printStackTrace();
} catch (NullPointerException e) {
// Currently an NPE is thrown when the Camera2API is used but not supported on the
// device this code runs.
ErrorDialog.newInstance(getString(R.string.camera_error))
.show(getChildFragmentManager(), FRAGMENT_DIALOG);
}
}
...
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
= new ImageReader.OnImageAvailableListener() {
@Override
public void onImageAvailable(ImageReader reader) {//图片有效回调
mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));//通知ImageSaver线程保存图片，//reader.acquireNextImage()获取图片image
}
};
...
private void configureTransform(int viewWidth, int viewHeight) {//配置transformation，主要是矩阵旋转相关
Activity activity = getActivity();
if (null == mTextureView || null == mPreviewSize || null == activity) {
return;
}
int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
Matrix matrix = new Matrix();
RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
RectF bufferRect = new RectF(0, 0, mPreviewSize.getHeight(), mPreviewSize.getWidth());
float centerX = viewRect.centerX();
float centerY = viewRect.centerY();
if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {
bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
float scale = Math.max(
(float) viewHeight / mPreviewSize.getHeight(),
(float) viewWidth / mPreviewSize.getWidth());
matrix.postScale(scale, scale, centerX, centerY);
matrix.postRotate(90 * (rotation - 2), centerX, centerY);
} else if (Surface.ROTATION_180 == rotation) {
matrix.postRotate(180, centerX, centerY);
}
mTextureView.setTransform(matrix);//设置mTextureView的transformation
}
...
private void createCameraPreviewSession() {
try {
SurfaceTexture texture = mTextureView.getSurfaceTexture();//通过mTextureView获取SurfaceTexture。
assert texture != null;
// We configure the size of default buffer to be the size of camera preview we want.
texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());//设置SurfaceTexture大小,预览尺寸
// This is the output Surface we need to start preview.
Surface surface = new Surface(texture);//通过SurfaceTexture创建Surface来预览。
// We set up a CaptureRequest.Builder with the output Surface.
mPreviewRequestBuilder
= mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);//创建TEMPLATE_PREVIEW预览CaptureRequest.Builder
mPreviewRequestBuilder.addTarget(surface);//CaptureRequest.Builder中添加Surface，即mTextureView获取创建的Surface
// Here, we create a CameraCaptureSession for camera preview.
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
new CameraCaptureSession.StateCallback() {//创建会话
@Override
public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {//创建会话成功
// The camera is already closed
if (null == mCameraDevice) {
return;
}
// When the session is ready, we start displaying the preview.
mCaptureSession = cameraCaptureSession;//从onConfigured参数获取mCaptureSession
try {
// Auto focus should be continuous for camera preview.
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);//设置AF自动对焦模式
// Flash is automatically enabled when necessary.
setAutoFlash(mPreviewRequestBuilder);
// Finally, we start displaying the camera preview.
mPreviewRequest = mPreviewRequestBuilder.build();//转换为CaptureRequest
mCaptureSession.setRepeatingRequest(mPreviewRequest,
mCaptureCallback, mBackgroundHandler);//设置预览,setRepeatingRequest不断的重复mPreviewRequest请求捕捉画面，常用于预览或者连拍场景。
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(//创建会话失败
@NonNull CameraCaptureSession cameraCaptureSession) {
showToast("Failed");
}
}, null
);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
...
private CameraCaptureSession.CaptureCallback mCaptureCallback
= new CameraCaptureSession.CaptureCallback() {//预览回调
private void process(CaptureResult result) {
switch (mState) {
case STATE_PREVIEW: {//预览状态，则什么都不做
// We have nothing to do when the camera preview is working normally.
break;
}
case STATE_WAITING_LOCK: {//等待焦点被锁时，由设置拍照流时设置的STATE_WAITING_LOCK
Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
if (afState == null) {
captureStillPicture();//进行拍照
} else if (CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED == afState ||
CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED == afState) {
// CONTROL_AE_STATE can be null on some devices
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null ||
aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {
mState = STATE_PICTURE_TAKEN;
captureStillPicture();
} else {
runPrecaptureSequence();
}
}
break;
}
case STATE_WAITING_PRECAPTURE: {
// CONTROL_AE_STATE can be null on some devices
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null ||
aeState == CaptureResult.CONTROL_AE_STATE_PRECAPTURE ||
aeState == CaptureRequest.CONTROL_AE_STATE_FLASH_REQUIRED) {
mState = STATE_WAITING_NON_PRECAPTURE;
}
break;
}
case STATE_WAITING_NON_PRECAPTURE: {
// CONTROL_AE_STATE can be null on some devices
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null || aeState != CaptureResult.CONTROL_AE_STATE_PRECAPTURE) {
mState = STATE_PICTURE_TAKEN;
captureStillPicture();
}
break;
}
}
}
...
private void captureStillPicture() {//进行拍照
try {
final Activity activity = getActivity();
if (null == activity || null == mCameraDevice) {
return;
}
// This is the CaptureRequest.Builder that we use to take a picture.
final CaptureRequest.Builder captureBuilder =
mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);//设置TEMPLATE_STILL_CAPTURE拍照CaptureRequest.Builder
captureBuilder.addTarget(mImageReader.getSurface());//添加拍照mImageReader为Surface
// Use the same AE and AF modes as the preview.//设置AF和AE
captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
setAutoFlash(captureBuilder);
// Orientation 设置成像方向
int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));//设置图片方向
CameraCaptureSession.CaptureCallback CaptureCallback
= new CameraCaptureSession.CaptureCallback() {//拍照流程执行完成回调
@Override
public void onCaptureCompleted(@NonNull CameraCaptureSession session,
@NonNull CaptureRequest request,
@NonNull TotalCaptureResult result) {
showToast("Saved: " + mFile);//提示拍照图片已经保存
Log.d(TAG, mFile.toString());
unlockFocus();//释放焦点锁，重新开启预览。
}
};
mCaptureSession.stopRepeating();//停止预览,停止任何一个正常进行的重复请求。
mCaptureSession.abortCaptures();//中断Capture,尽可能快的取消当前队列中或正在处理中的所有捕捉请求。
mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);//重新Capture进行拍照，这时mImageReader的回调会执行并保存图片
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
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