android camera2 process each frame and display its preview

问题

I use the https://github.com/googlesamples/android-Camera2Basic, but try to modify it in a way that I could get access to each frame before it is drawn on the surfaceview. I understood, I should add additional surface (ImageReader.getSurface()), and read the frame from it in this callback:

private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
            = new ImageReader.OnImageAvailableListener() {

        @Override
        public void onImageAvailable(ImageReader reader) {

           Log.d("Img", "onImageAvailable");
            mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));
        }

    };

The problem is this callback gets called only when the image is capture by the user and not on eacg frame that is sent to preview screen from camera.

Here is what I tried to add:

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);

            // Here, we create a CameraCaptureSession for camera preview.
            mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
                    new CameraCaptureSession.StateCallback() {

                        @Override
                        public void onConfigured(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.
                                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                                        CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

                                // Finally, we start displaying the camera preview.
                                mPreviewRequest = mPreviewRequestBuilder.build();
                                mCaptureSession.setRepeatingRequest(mPreviewRequest,
                                        mCaptureCallback, mBackgroundHandler);
                                //mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
                            showToast("Failed");
                        }
                    }, null
            );

            /**TODO added for capturing aeach frame*/
            // This is the CaptureRequest.Builder that we use to take a picture.
            final CaptureRequest.Builder captureBuilder =
                    mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            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);
            captureBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                    CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

            /**end added for capture each frame*/


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

回答1:

Instead of creating a new instance of CaptureRequest.Builder, just add the ImageReader's Surface to the mPreviewRequestBuilder's output target.

来源：https://stackoverflow.com/questions/31232008/android-camera2-process-each-frame-and-display-its-preview