IBM FileNet P8 provides Java APIs to deal with the content engine (CE)
my question is: are these APIs compatible with Android? can I use these APIs within my Android application ? if not, are there any alternatives ?
You can try to use CEWS API.
You cat try to use CMIS interface (if CMIS can cover your requirements and if you find the impelemntations of CMIS cliet for Android)
You can use ready Content Navigator application from Google Play to work with P8 repository.
You can customize ICN and use it in mobile browser or embeded via JavaScript in your application.