android - 使用camera2 API无需预览即可捕获图片

我要实现的是在不显示预览的情况下捕获图片，将输出直接发送到ImageReader。
我已将Camera2Basic example用作起点。
但是，从未调用我的ImageReader的回调，因此没有图像发送到其Surface。
我真的需要先显示预览吗？

这是摄像机代码，按照异步回调的流程进行排序:

private ImageReader imageReader;
private Handler backgroundHandler;
private HandlerThread backgroundThread;
private String cameraId;
private CameraDevice cameraDevice;
private CameraCaptureSession cameraCaptureSession;
    @Override
    public void onCreate() {
        setupCamera2();
    }

    private void setupCamera2() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        try {

            for (String cameraId : manager.getCameraIdList()) {
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);

            if (characteristics.get(CameraCharacteristics.LENS_FACING) != CameraCharacteristics.LENS_FACING_FRONT) {
                continue;
            }

            this.cameraId = cameraId;

            int[] picSize = Settings.getPictureSize();
            int picWidth = picSize[0];
            int picHeight = picSize[1];

            imageReader = ImageReader.newInstance(picWidth, picHeight, ImageFormat.JPEG, 2);
            imageReader.setOnImageAvailableListener(onImageAvailableListener, backgroundHandler);
            }

        } catch (CameraAccessException | NullPointerException e) {
            e.printStackTrace();
        }
    }


    private void openCamera2() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {

            manager.openCamera(cameraId, cameraStateCallback, backgroundHandler);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }



    private final CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice device) {
            cameraDevice = device;
            createCameraCaptureSession();
        }

        @Override
        public void onDisconnected(CameraDevice cameraDevice) {}

        @Override
        public void onError(CameraDevice cameraDevice, int error) {}
    };



    private void createCaptureSession() {
        List<Surface> outputSurfaces = new LinkedList<>();
        outputSurfaces.add(imageReader.getSurface());

        try {

            cameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(CameraCaptureSession session) {
                    cameraCaptureSession = session;
                }

                @Override
                public void onConfigureFailed(CameraCaptureSession session) {}
            }, null);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }


    private final ImageReader.OnImageAvailableListener onImageAvailableListener = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            createCaptureRequest();
        }
    };


    private void createCaptureRequest() {
        try {

            CaptureRequest.Builder requestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            requestBuilder.addTarget(imageReader.getSurface());

            // Focus
            requestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

            // Orientation
            int rotation = windowManager.getDefaultDisplay().getRotation();
            requestBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));

            cameraCaptureSession.capture(requestBuilder.build(), camera2Callback, null);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

最佳答案

您应该在“onConfigured”功能中捕获照片，而不是onImageAvailable。

public void onConfigured(CameraCaptureSession session) {
            cameraCaptureSession = session;
            createCaptureRequest();
        }

在此功能“onImageAvailable”中，您应该保存图像，

Image image = mImageReader.acquireLatestImage();
ByteBuffer buffer = image.getPlanes()[0].getBuffer();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
try {
    save(bytes, file);
} catch (IOException e) {
    e.printStackTrace();
}
image.close();

在session.capture()之后将调用“onImageAvailable”函数。