Pure code scanner is a QR and bar code scanner that is light, fast, free, offline and ad-free.
It is powered by Google's Mobile Vision API(https://developers.google.com/vision/) and supports a wide range of QR and bar code formats.
You can find it in Play store at: https://play.google.com/store/apps/details?id=in.sureshkumarkv.purecodescanner