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image
前面几篇文章实现了相机的预览，对预览中出现的问题及需要注意的事项进行了梳理。
本篇文章对相机的拍照流程、拍照方向及屏幕旋转时的适配问题进行梳理。
初始化相机和view
这里选择最大的相机输出尺寸作为拍照尺寸和预览尺寸。
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
initCamera();
initViews(view);
}
private void initCamera() {
cameraManager = CameraUtils.getInstance().getCameraManager();
cameraId = CameraUtils.getInstance().getBackCameraId();
outputSizes = CameraUtils.getInstance().getCameraOutputSizes(cameraId, SurfaceTexture.class);
photoSize = outputSizes.get(0);
}
private void initViews(View view) {
btnPhoto = view.findViewById(R.id.btn_photo);
btnPhoto.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
takePhoto();
}
});
previewView = view.findViewById(R.id.preview_view);
}
启动/释放相机
在 fragment 的 onResume 生命周期函数中启动相机，在 onPause 中释放相机。
@Override
public void onResume() {
super.onResume();
if (previewView.isAvailable()) {
openCamera();
} else {
previewView.setSurfaceTextureListener(surfaceTextureListener);
}
}
@Override
public void onPause() {
releaseCamera();
super.onPause();
}
屏幕旋转时适配预览窗口和方向
启动相机时需要根据此时屏幕的显示方向（横屏/竖屏）调整预览窗口的大小和显示方向。
- 调整预览窗口的大小，可以参考之前解决预览界面拉伸的文章，里面有描述。
- 调整预览方向：计算出预览窗口到相机输出窗口的变换矩阵。
- 先将两个窗口的中心平移到同一点；
- 设置两窗口缩放模式；
- 计算缩放比例和旋转角度；
- 将变换矩阵应用到预览窗口上。
@SuppressLint("MissingPermission")
private void openCamera() {
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED) {
requestCameraPermission();
} else {
try {
//根据屏幕的显示方向调整预览窗口大小
displayRotation = ((Activity) getContext()).getWindowManager().getDefaultDisplay().getOrientation();
if (displayRotation == Surface.ROTATION_0 || displayRotation == Surface.ROTATION_180) {
previewView.setAspectRation(photoSize.getHeight(), photoSize.getWidth());
}else {
previewView.setAspectRation(photoSize.getWidth(), photoSize.getHeight());
}
//根据屏幕的显示方向调整预览方向
configureTransform(previewView.getWidth(), previewView.getHeight());
cameraManager.openCamera(cameraId, cameraStateCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
Log.d(TAG, "相机访问异常");
}
}
}
private void configureTransform(int viewWidth, int viewHeight) {
Activity activity = getActivity();
if (null == previewView || null == photoSize || 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, photoSize.getHeight(), photoSize.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 / photoSize.getHeight(),
(float) viewWidth / photoSize.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);
}
previewView.setTransform(matrix);
}
surfaceTextureListener 之前的文章也提过，这里给出代码
TextureView.SurfaceTextureListener surfaceTextureListener = new TextureView.SurfaceTextureListener() {
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
//启动相机
openCamera();
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
configureTransform(width, height);
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
return false;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
};
还有相机打开的状态回调监听，成功打开后，初始化预览、拍照用的Surface 以及 保存拍照数据用的 ImageReader。
CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(CameraDevice camera) {
Log.d(TAG, "相机已启动");
//初始化拍照用的 ImageReader 和 Surface
initReaderAndSurface();
cameraDevice = camera;
try {
//初始化预览 Surface
SurfaceTexture surfaceTexture = previewView.getSurfaceTexture();
if (surfaceTexture == null){
return;
}
surfaceTexture.setDefaultBufferSize(photoSize.getWidth(), photoSize.getHeight());//设置SurfaceTexture缓冲区大小
previewSurface = new Surface(surfaceTexture);
previewRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
previewRequestBuilder.addTarget(previewSurface);
previewRequest = previewRequestBuilder.build();
cameraDevice.createCaptureSession(Arrays.asList(previewSurface, photoSurface), sessionsStateCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
Log.d(TAG, "相机访问异常");
}
}
@Override
public void onDisconnected(CameraDevice camera) {
Log.d(TAG, "相机已断开连接");
}
@Override
public void onError(CameraDevice camera, int error) {
Log.d(TAG, "相机打开出错");
}
};
需要注意的是别忘了给 ImageReader 添加监听器。
当拍照数据可用时会回调该监听，在监听的回调方法中，添加图片的处理保存逻辑即可。
private void initReaderAndSurface() {
//初始化拍照 ImageReader
photoReader = ImageReader.newInstance(photoSize.getWidth(), photoSize.getHeight(), ImageFormat.JPEG, 2);
photoReader.setOnImageAvailableListener(photoReaderImgListener, null);
photoSurface = photoReader.getSurface();
}
ImageReader.OnImageAvailableListener photoReaderImgListener = new ImageReader.OnImageAvailableListener() {
@Override
public void onImageAvailable(ImageReader reader) {
writeImageToFile();
}
};
private void writeImageToFile() {
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.WRITE_EXTERNAL_STORAGE)
!= PackageManager.PERMISSION_GRANTED) {
requestStoragePermission();
} else {
String filePath = Environment.getExternalStorageDirectory() + "/DCIM/Camera/001.jpg";
Image image = photoReader.acquireNextImage();
if (image == null) {
return;
}
ByteBuffer byteBuffer = image.getPlanes()[0].getBuffer();
byte[] data = new byte[byteBuffer.remaining()];
byteBuffer.get(data);
FileOutputStream fos = null;
try {
fos = new FileOutputStream(new File(filePath));
fos.write(data);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
fos.close();
fos = null;
} catch (IOException e) {
e.printStackTrace();
} finally {
image.close();
image = null;
}
}
}
}
相机会话状态回调之前也说明过，在会话创建成功时，开始重复请求，以获得连续的预览。
CameraCaptureSession.StateCallback sessionsStateCallback = new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(CameraCaptureSession session) {
if (null == cameraDevice) {
return;
}
captureSession = session;
try {
captureSession.setRepeatingRequest(previewRequest, null, null);
} catch (CameraAccessException e) {
e.printStackTrace();
Log.d(TAG, "相机访问异常");
}
}
@Override
public void onConfigureFailed(CameraCaptureSession session) {
Log.d(TAG, "会话注册失败");
}
};
拍照
经过上述步骤，可以在屏幕旋转时也能保证正常的预览窗口大小和预览方向。
拍照按钮的点击事件监听函数 takePhoto() 主要有三个步骤。
- 首先需要根据屏幕显示方向，矫正拍照方向
- 然后停止相机预览，创建拍照请求进行拍照
- 拍照成功后，重启相机预览
其中，屏幕显示方向和拍照方向的对应关系用 PHOTO_ORTATION 定义。
private static final SparseIntArray PHOTO_ORITATION = new SparseIntArray();
static {
PHOTO_ORITATION.append(Surface.ROTATION_0, 90);
PHOTO_ORITATION.append(Surface.ROTATION_90, 0);
PHOTO_ORITATION.append(Surface.ROTATION_180, 270);
PHOTO_ORITATION.append(Surface.ROTATION_270, 180);
}
private void takePhoto() {
try {
photoRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
cameraOritation = PHOTO_ORITATION.get(displayRotation);
photoRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION, cameraOritation);
photoRequestBuilder.addTarget(photoSurface);
photoRequest = photoRequestBuilder.build();
captureSession.stopRepeating();
captureSession.capture(photoRequest, sessionCaptureCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
Log.d(TAG, "相机访问异常");
}
}
CameraCaptureSession.CaptureCallback sessionCaptureCallback = new CameraCaptureSession.CaptureCallback() {
@Override
public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
try {
captureSession.setRepeatingRequest(previewRequest, null, null);
} catch (CameraAccessException e) {
e.printStackTrace();
Log.d(TAG, "相机访问异常");
}
}
};
总结
整个流程并不是多复杂，主要就是要注意手机屏幕旋转时的预览窗口、方向适配，以及拍照方向的矫正。
到目前为止，相机预览、拍照方面的流程和注意事项基本梳理完毕，后续梳理相机特性控制和录像方面的知识。
