Camera.PreviewCallback equivalent in Camera2 API

You can start from the Camera2Basic sample code from Google.

You need to add the surface of the ImageReader as a target to the preview capture request:

//set up a CaptureRequest.Builder with the output SurfacemPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);mPreviewRequestBuilder.addTarget(surface);mPreviewRequestBuilder.addTarget(mImageReader.getSurface());

After that, you can retrieve the image in the ImageReader.OnImageAvailableListener:

private final ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {    @Override    public void onImageAvailable(ImageReader reader) {        Image image = null;        try {            image = reader.acquireLatestImage();            if (image != null) {                ByteBuffer buffer = image.getPlanes()[0].getBuffer();                Bitmap bitmap = fromByteBuffer(buffer);                image.close();            }        } catch (Exception e) {            Log.w(LOG_TAG, e.getMessage());        }    }};

To get a Bitmap from the ByteBuffer:

Bitmap fromByteBuffer(ByteBuffer buffer) {    byte[] bytes = new byte[buffer.capacity()];    buffer.get(bytes, 0, bytes.length);    return BitmapFactory.decodeByteArray(bytes, 0, bytes.length);}

Yes, use the ImageReader class.

Create an ImageReader using the format ImageFormat.YUV_420_888 and your desired size (make sure you select a size that's supported by the camera device you're using).

Then use ImageReader.getSurface() for a Surface to provide to CameraDevice.createCaptureSession(), along with your other preview outputs, if any.

Finally, in your repeating capture request, add the ImageReader provided surface as a target before setting it as the repeating request in your capture session.