On http://docs.opencv.org/3.1.0/d5/df8/tutorial_dev_with_OCV_on_Android.html it states
According to this approach all OpenCV binaries are included into your application package. It is designed mostly for development purposes. This approach is deprecated for the production code, release package is recommended to communicate with OpenCV Manager via the async initialization described
which (for me) translates to
Building Android OpenCV yourself is deprecated.
The problem is, that the official releases (neither in the manager nor in the provided libs) don't contain the contrib modules despite the build bot seems to build them everytime.
To the release management team:
Could you include the pre-built OpenCV contrib modules in the next release packages? If not in the OpenCV manager, at least in the libs?