just a few more details: dlib is a massive "deep learning" (dl - get it?) c++ library, offering - among others - face recognition. the github link referred to above is a python api into that library.
there is an android port out there. perhaps some reverse engineering interest there...
if there were a javacpp preset for the original c++ code, it could be integrated inline into a b4a project (as anyone who has worked directly with opencv, tesseract or leptonica in c/c++ is aware). successfully completing the javacpp has, apparently, proven formidable over the past few years.