Android Camera2 學習01_API 的簡單描述和呼叫（預覽、拍照、錄影）
Android 5.1 以後，添加了Camera2 的API,能夠滿足更多控制camera的場景。當然，相對應camera1的呼叫，也變的複雜一點。
一、涉及到的關鍵類
CameraManager -------------- 獲取連線的camera情況，執行開啟攝像頭的操作；
CameraDevice -------------- 當前連線的攝像頭物件；
CaptureRequest -------------- camera資料的請求，比如預覽、拍照、錄影等；
CaptureSession -------------- 傳送請求後，就建立了一個會話，可以在當前建立的會話上切換各種請求，不需要的時候可以執行關閉；
二、程式碼實現
下面程式碼是基於Google提供的demohttps://github.com/googlesamples/android-Camera2Basic
後面自己個人又建了個獨立的分支，程式碼都是基於Google Demo 來的https://github.com/yorkZJC/AndroidCamera2Sample
Camera2BaseFragment.java
2.1這裡採用的是TextureView來進行顯示，在onResume()的時候，進行判斷，如果當前TextureView 可用了，則執行開啟攝像頭的操作，否則等待TextureView available，第一次開啟的是，TextureView還沒建立完成，所以會在TextureView available回撥中執行開啟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接下來看下openCamera()的實現
這邊完成了camera資訊的獲取的配置，並呼叫CameraManager 的openCamera開啟攝像頭，camera開啟狀態在CameraDevice.StateCallback中進行回撥.
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開啟的回撥中，可以獲取到當前的camera對應的CameraDevice,在onOpened()中執行開啟預覽的操作。
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下來就是開啟預覽的過程，主要做了下面幾件事情:
1、預覽影象顯示在哪裡，這就需要繫結surface,這裡可以進行多個surface的繫結，如果是上層需要拿到預覽資料，則可以設定ImageReader的surface進去；
2、傳送預覽請求；
3、建立預覽會話；
完成這幾步，我們就可以看到預覽影象了。
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可以設定多個target，如果需要拿到實時的預覽資料，則把imageReader 的surface 也設進去
// 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，拍照時通過ImageReader返回jpeg資料給上層，交由上層進行儲存；
如下面程式碼所示：
1、首先需要初始化一個JPEG型別的ImageReader，用來接收底層資料回撥；
2、設定CameraDevice.TEMPLATE_STILL_CAPTURE 型別的請求，請求拍照；請求成功後，我們需要恢復正常的預覽型別請求；
3、在ImageReader回撥中將接收到的jpeg資料進行儲存；
/**
* 初始化一個jpeg型別的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);
//將接收到的資料交由獨立的執行緒進行檔案的儲存操作
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 =
//設定拍照請求
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) {
//拍照請求成功後，恢復正常的預覽模式
startPreview();
mCapturing = false;
}
};
mPreviewSession.stopRepeating();
mPreviewSession.abortCaptures();
mPreviewSession.capture(mPreviewBuilder.build(),captureCallback , mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
2.6錄影
Android API文件（https://developer.android.google.cn/reference/android/hardware/camera2/package-summary?hl=en）描述有下面這麼一段話，我們可以看到MediaRecorder 的surface也是可以作為target Surface進行資料的請求的。那就很簡單了，錄影編碼需要資料來源，而這個source就是通過MediaRecorder.getsurface,然後把該surface設定為target surface,那麼MediaRecorder就可以拿到Camera資料了。
下面看下具體的程式碼實現：
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、寫在後面
看了上面簡單的程式碼流程，我們應該有這樣簡單的概念。對Camera的操作，無非就是獲取到硬體裝置相關屬性，比如當前掛載了哪些攝像頭，攝像頭支援哪些解析度等屬性，這個我們需要用到CameraManager來獲取；
獲取到Camera相關屬性後，那麼就需要對硬體裝置進行操作，操作就是開啟Camera,獲取預覽資料這些了，通過CameraManager，我們能開啟對應Id的camera,然後獲取到該id對應的Camera裝置例項，這個就是CameraDevice了；
那麼接下來就是怎麼怎麼把Camera資料顯示到UI上，這時就用到Surface了，我們可以這樣理解，Surface是影象顯示的介質，Camera2 API 允許我們設定多個Surface為輸出目標，比如上面我們說的ImageReader、SurfaceTexutre、MediaRecorder相關的Surface都可以設為目標Surface,底層會幫我們進行資料的填充和顯示。這些Surface我們需要預先初始化好引數;
那麼有了顯示的載體後，就可以進行顯示了，Camera2裡面就用到了個CaptureRequest 來觸發資料的請求，這個request又可以根據自己的使用場景設定不同的請求型別，比如是 預覽場景，則可以設定請求型別為 CameraDevice.TEMPLATE_PREVIEW，錄影場景下，則設定為CameraDevice.TEMPLATE_RECORD，拍照場景下，則設定為CameraDevice.TEMPLATE_STILL_CAPTURE；
完成了上面這些後，還需要最後一步，就是建立會話了，也就是CaptureSession。我們可以理解為，上面所做的準備，都是為了建立會話，建立了會話後，和Camera之間的互動才真正建立起來。這個會話可以隨時關閉，也可以修改引數。
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