一.介绍：
Camera2 是 Android L 的一个重大更新，重新定义了相机 API，也重构了相机 API 的架构，但使用起来，还是很复杂。 官方demo地址：Camera2
二.流程：
下面根据官方demo来详细了解下Camera2的拍照流程
1.设置预览图的尺寸
mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
rotatedPreviewWidth, rotatedPreviewHeight, maxPreviewWidth,
maxPreviewHeight, largest);
2.创建一个用于处理拍照图片处理的ImageReder
mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
ImageFormat.JPEG, /*maxImages*/2);
mImageReader.setOnImageAvailableListener(
mOnImageAvailableListener, mBackgroundHandler);
这里会为ImageReder设置一个OnImageAvailableListener的监听器，一旦ImageReder获取到相机设备传过来的图像，就会回调该监听器的onImageAvailable方法，在onImageAvailable方法的ImageReader参数就携带了拍照所得的图像
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
= new ImageReader.OnImageAvailableListener() {
@Override
public void onImageAvailable(ImageReader reader) {
mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));
}
};
3.获取CamerManager对象，并打开相机设备
CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
try {
//这里把相机加了一把锁，因为可能会有多个应用用到相机设备，在指定时间内，没有拿到许可就会抛异常
if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
throw new RuntimeException("Time out waiting to lock camera opening.");
}
//这里回传入一个CameraDevice.StateCallback对象mStateCallback，这个就是拿到相机设备成功失败的回调
manager.openCamera(mCameraId, mStateCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
} catch (InterruptedException e) {
throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
}
4.获取到相机设备,创建用于显示预览图片的Surface和一个适合相机预览窗口的请求
SurfaceTexture texture = mTextureView.getSurfaceTexture();
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());
// This is the output Surface we need to start preview.
Surface surface = new Surface(texture);
// We set up a CaptureRequest.Builder with the output Surface.
mPreviewRequestBuilder
= mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mPreviewRequestBuilder.addTarget(surface);
5.创建一个CameraCaptureSession
/**
第一个参数List<Surface>,surface用于显示预览图的，就是第四步中创建的那个Surface,mImageReader.getSurface()使用来处理拍照返回的图片的Surface,
第二个参数callback， CameraCaptureSession.StateCallback对象，创建session成功与否的回调
第三个参数，Handler指定回调的线程,null表示当前线程
*/
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),callback， mImageReader.getSurface()),
, null
);
6.在 CameraCaptureSession.StateCallback接收到CameraCaptureSession并发送预览请求，
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
// The camera is already closed
if (null == mCameraDevice) {
return;
}
// When the session is ready, we start displaying the preview.
mCaptureSession = cameraCaptureSession;
try {
// Auto focus should be continuous for camera preview.
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
// Flash is automatically enabled when necessary.
setAutoFlash(mPreviewRequestBuilder);
// Finally, we start displaying the camera preview.
mPreviewRequest = mPreviewRequestBuilder.build();
// 通过此捕获会话无休止地重复捕获图像，即预览请求 mCaptureSession.setRepeatingRequest(mPreviewRequest,
mCaptureCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(
@NonNull CameraCaptureSession cameraCaptureSession) {
showToast("Failed");
}
}
到此，我们的TextureView就可以显示预览的图像了
7.拍照
try {
// This is how to tell the camera to lock focus,自动对焦
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
CameraMetadata.CONTROL_AF_TRIGGER_START);
// Tell #mCaptureCallback to wait for the lock.
mState = STATE_WAITING_LOCK;
//提交要由相机设备捕获的图像的请求 mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback,
mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
在mCaptureCallback中，调用captureStillPicture（）
private void captureStillPicture() {
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);
//将mImageReader的surface添加到此请求的目标列表中,这时拍照所返回的图片就会交由mImageReader的mOnImageAvailableListener处理
captureBuilder.addTarget(mImageReader.getSurface());
// Use the same AE and AF modes as the preview.
captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
setAutoFlash(captureBuilder);
// Orientation
int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));
CameraCaptureSession.CaptureCallback CaptureCallback
= new CameraCaptureSession.CaptureCallback() {
//拍照事务完成后回调这个方法
@Override
public void onCaptureCompleted(@NonNull CameraCaptureSession session,
@NonNull CaptureRequest request,
@NonNull TotalCaptureResult result) {
showToast("Saved: " + mFile);
Log.d(TAG, mFile.toString());
unlockFocus();
}
};
mCaptureSession.stopRepeating();
mCaptureSession.abortCaptures();
mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
至此，拍照也已完成
三.总结
这仅仅是对谷歌Camera2官方Demo的一个简单学习，关于Camera2中的各种操作还有许多学习的地方，包括美颜，磨皮各种模式的实现