Everything written here is wrong.
Starting from v1.09, B4XPages work with AppCompat.
I still don't recommend using AppCompat, as Android 4 devices are no longer relevant, and almost everything that can be done with AppCompat, can also be done without it.
The only thing B4XPages can't do on Android is change orientation. Otherwise it is a standard app with a single Activity that behaves like any other app.
This example demonstrates how you can add a full screen button to a video. Clicking on the button, starts a new landscape activity and it then uses the native switchTargetView method to reuse the same player in the new SimpleExoPlayerView. There is also some calculations involved with adding the...