Added preview callback

[Sumsar]

Callback to get preview byte data

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please let us know the company's name.

[Sumsar]

I signed it!

[xCatG]

Hi, I don't think NV21 is supported in Camera2. It should be YUV_420_888 in Camera2 case. It cashed on my N5X with Caused by: java.lang.IllegalArgumentException: NV21 format is not supported

[aryarohit07]

Reference on the above comment

[jackyhieu1211]

Camera1 on device HTC Butterfly 4.3 API 18 not call
mCamera.setPreviewCallback(new Camera.PreviewCallback() {
@OverRide
public void onPreviewFrame(byte[] data, Camera camera) {
Timber.e("onPreviewFrame");
final Camera.Parameters parameters = camera.getParameters();
final int width = parameters.getPreviewSize().width;
final int height = parameters.getPreviewSize().height;
mCallback.onPreviewFrame(data, parameters.getPreviewFormat(), width, height);
}
});

[jackyhieu1211]

I fix it

@OverRide
public void onSurfaceChanged() {
if (mCamera != null) {
setUpPreview();
adjustCameraParameters();
mCamera.setPreviewCallback(Camera1.this);
}
}

[doug-precocity]

Some image formats have multiple planes, including YUV420_888 (the default for Camera2). All planes need to be included in the output byte array.

[hardysim]

Any progress on this? I'm trying to get ML Kit to work but the example code uses Camera 1 API and lags terribly and this here seems like the perfect match but is not yet included 😭.