This is not a Reference Client, it's c-toxcore for Android.
This is now also a Tox Client for Android.
Use Weblate: https://hosted.weblate.org/engage/trifa-a-tox-client-for-android/
To get offline messages for your TRIfA App, install ToxProxy on your raspberryPi and leave it running at home.
See the installation instructions here
and select the "android-refimpl-app" subdir:
the latest Development Snapshot can be downloaded from CircleCI, here