Android Camera开发序列：Camera2 API 的简单描述和调用（预览、拍照、录像）
Android 5.1 以后，添加了Camera2 的API,能够满足更多操纵camera的场景。当然，相对应camera1的调用，也变的复杂一点。
一、涉及到的关键类
CameraManager -------------- 获取连接的camera情况，执行打开摄像头的操作；
CameraDevice -------------- 当前连接的摄像头对象；
CaptureRequest -------------- camera数据的请求，比如预览、拍照、录像等 ；
CaptureSession -------------- 发送请求后，就建立了一个会话，可以在当前建立的会话上切换各种请求，不需要的时候可以执行关闭；
二、代码实现
下面代码是基于Google提供的demo https://github.com/googlesamples/android-Camera2Basic
后面自己个人又建了个独立的分支，代码都是基于Google Demo 来的 https://github.com/yorkZJC/AndroidCamera2Sample
Camera2BaseFragment.java
2.1 这里采用的是TextureView来进行显示，在onResume()的时候，进行判断，如果当前TextureView 可用了，则执行打开摄像头的操作，否则等待TextureView available，第一次打开的是，TextureView还没创建完成，所以会在TextureView available回调中执行打开camera的操作。
@Override
public void onResume() {
super.onResume();
startBackgroundThread();
if (mTextureView.isAvailable()) {
openCamera(mTextureView.getWidth(), mTextureView.getHeight());
} else {
mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
}
}
private final TextureView.SurfaceTextureListener mSurfaceTextureListener
= new TextureView.SurfaceTextureListener() {
@Override
public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {
openCamera( width, height);
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture texture, int width, int height) {
configureTransform(width, height);
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
return true;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture texture) {
}
};
2.2 接下来看下openCamera()的实现
这边完成了camera信息的获取的配置，并调用CameraManager 的openCamera打开摄像头，camera打开状态在CameraDevice.StateCallback中进行回调.
private void openCamera(int width, int height) {
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED) {
requestCameraPermission();
return;
}
setUpCameraOutputs(width, height);
configureTransform(width, height);
Activity activity = getActivity();
CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
try {
if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
throw new RuntimeException("Time out waiting to lock back camera opening.");
}
manager.openCamera(mCameraId,mStateCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
} catch (InterruptedException e) {
throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
}
}
2.3 在camera打开的回调中，可以获取到当前的camera对应的CameraDevice,在onOpened()中执行打开预览的操作。
private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(@NonNull CameraDevice cameraDevice) {
// This method is called when the camera is opened. We start camera preview here.
mCameraOpenCloseLock.release();
mCameraDevice = cameraDevice;
createCameraPreviewSession();
}
@Override
public void onDisconnected(@NonNull CameraDevice cameraDevice) {
mCameraOpenCloseLock.release();
cameraDevice.close();
mCameraDevice = null;
}
@Override
public void onError(@NonNull CameraDevice cameraDevice, int error) {
mCameraOpenCloseLock.release();
cameraDevice.close();
mCameraDevice = null;
Activity activity = getActivity();
if (null != activity) {
activity.finish();
}
}
};
2.4 下来就是打开预览的过程，主要做了下面几件事情:
1、预览图像显示在哪里，这就需要绑定surface,这里可以进行多个surface的绑定，如果是上层需要拿到预览数据，则可以设置ImageReader的surface进去；
2、发送预览请求；
3、建立预览会话；
完成这几步，我们就可以看到预览图像了。
private void createCameraPreviewSession() {
try {
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);
//request builder可以设置多个target，如果需要拿到实时的预览数据，则把imageReader 的surface 也设进去
// mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
// Here, we create a CameraCaptureSession for camera preview.
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
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.
mPreviewCaptureSession = 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();
// mPreviewCaptureSession.setRepeatingRequest(mPreviewRequest,
// mCaptureCallback, mBackgroundHandler);
mPreviewCaptureSession.setRepeatingRequest(mPreviewRequest,
null, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(
@NonNull CameraCaptureSession cameraCaptureSession) {
showToast("Failed");
}
}, null
);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
2.5 拍照
Camera2 的API，拍照时通过ImageReader返回jpeg数据给上层，交由上层进行保存；
如下面代码所示：
1、首先需要初始化一个JPEG类型的ImageReader，用来接收底层数据回调；
2、设置CameraDevice.TEMPLATE_STILL_CAPTURE 类型的请求，请求拍照；请求成功后，我们需要恢复正常的预览类型请求；
3、在ImageReader回调中将接收到的jpeg数据进行保存；
/**
* 初始化一个jpeg类型的imageReader
**/
private void initJpegImageReader(int width, int height) {
StreamConfigurationMap map = mCameraCharacteristics.get(
CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
if (map == null) {
return;
}
Size largest = Collections.max(
Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
new CompareSizesByArea());
mJpegCpatureWidth = largest.getWidth();
mJpegCaptureHeight = largest.getHeight();
mJpegImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
ImageFormat.JPEG, 2);
mJpegImageReader.setOnImageAvailableListener(mJpegImageAvailableListener, mBackgroundHandler);
}
private final ImageReader.OnImageAvailableListener mJpegImageAvailableListener = new ImageReader.OnImageAvailableListener() {
@Override
public void onImageAvailable(ImageReader reader) {
Log.v(TAG, "--- mJpegImageAvailableListener();reader: " + reader);
Image image = reader.acquireLatestImage();
if(image == null){
return;
}
ByteBuffer buffer = image.getPlanes()[0].getBuffer();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
//将接收到的数据交由独立的线程进行文件的保存操作
mBackgroundHandler.post(new ImageSaver(bytes,mJpegCpatureWidth,mJpegCaptureHeight, generateJpegFile(),mCaptureListener));
image.close();
}
};
private void captureStillPicture() {
try {
if (null == mCameraDevice || mCapturing || mPreviewSession == null) {
return;
}
mCapturing = true;
// This is the CaptureRequest.Builder that we use to take a picture.
mPreviewBuilder =
//设置拍照请求
mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
mPreviewBuilder.addTarget(mJpegImageReader.getSurface());
// Use the same AE and AF modes as the preview.
// mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE,
// CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
// setAutoFlash(captureBuilder);
// Orientation
int rotation = 0;//activity.getWindowManager().getDefaultDisplay().getRotation();
mPreviewBuilder.set(CaptureRequest.JPEG_ORIENTATION, 0);
CameraCaptureSession.CaptureCallback captureCallback
= new CameraCaptureSession.CaptureCallback() {
@Override
public void onCaptureCompleted(@NonNull CameraCaptureSession session,
@NonNull CaptureRequest request,
@NonNull TotalCaptureResult result) {
//拍照请求成功后，恢复正常的预览模式
startPreview();
mCapturing = false;
}
};
mPreviewSession.stopRepeating();
mPreviewSession.abortCaptures();
mPreviewSession.capture(mPreviewBuilder.build(),captureCallback , mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
2.6 录像
Android API文档（https://developer.android.google.cn/reference/android/hardware/camera2/package-summary?hl=en）描述有下面这么一段话，我们可以看到MediaRecorder 的surface也是可以作为target Surface进行数据的请求的。那就很简单了，录像编码需要数据来源，而这个source就是通过MediaRecorder.getsurface,然后把该surface设置为target surface,那么MediaRecorder就可以拿到Camera数据了。
下面看下具体的代码实现：
private void startRecordingVideo() {
if (null == mCameraDevice || !mTextureView.isAvailable() || null == mPreviewSize) {
return;
}
try {
closePreviewSession();
setUpMediaRecorder();
SurfaceTexture texture = mTextureView.getSurfaceTexture();
assert texture != null;
texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
mPreviewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
List<Surface> surfaces = new ArrayList<>();
// Set up Surface for the camera preview
Surface previewSurface = new Surface(texture);
surfaces.add(previewSurface);
mPreviewBuilder.addTarget(previewSurface);
// Set up Surface for the MediaRecorder
Surface recorderSurface = mMediaRecorder.getSurface();
surfaces.add(recorderSurface);
mPreviewBuilder.addTarget(recorderSurface);
// Start a capture session
// Once the session starts, we can update the UI and start recording
mCameraDevice.createCaptureSession(surfaces, new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
mPreviewSession = cameraCaptureSession;
updatePreview();
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
// UI
mButtonVideo.setText(R.string.stop);
mIsRecordingVideo = true;
// Start recording
mMediaRecorder.start();
}
});
}
@Override
public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
Activity activity = getActivity();
if (null != activity) {
Toast.makeText(activity, "Failed", Toast.LENGTH_SHORT).show();
}
}
}, mBackgroundHandler);
} catch (CameraAccessException | IOException e) {
e.printStackTrace();
}
}
三、写在后面
看了上面简单的代码流程，我们应该有这样简单的概念。对Camera的操作，无非就是获取到硬件设备相关属性，比如当前挂载了哪些摄像头，摄像头支持哪些分辨率等属性，这个我们需要用到CameraManager来获取；
获取到Camera相关属性后，那么就需要对硬件设备进行操作，操作就是打开Camera,获取预览数据这些了，通过CameraManager，我们能打开对应Id的camera,然后获取到该id对应的Camera设备实例，这个就是CameraDevice了；
那么接下来就是怎么怎么把Camera数据显示到UI上，这时就用到Surface了，我们可以这样理解，Surface是图像显示的介质，Camera2 API 允许我们设置多个Surface为输出目标，比如上面我们说的ImageReader、SurfaceTexutre、MediaRecorder相关的Surface都可以设为目标Surface,底层会帮我们进行数据的填充和显示。这些Surface我们需要预先初始化好参数;
那么有了显示的载体后，就可以进行显示了，Camera2里面就用到了个CaptureRequest 来触发数据的请求，这个request又可以根据自己的使用场景设置不同的请求类型，比如是 预览场景，则可以设置请求类型为 CameraDevice.TEMPLATE_PREVIEW，录像场景下，则设置为CameraDevice.TEMPLATE_RECORD，拍照场景下，则设置为CameraDevice.TEMPLATE_STILL_CAPTURE；
完成了上面这些后，还需要最后一步，就是建立会话了，也就是CaptureSession。我们可以理解为，上面所做的准备，都是为了建立会话，建立了会话后，和Camera之间的交互才真正建立起来。这个会话可以随时关闭，也可以修改参数。
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*本人从事Android Camera相关开发已有5年，
*目前在深圳上班，
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