I've been searching for any java based RTP/RTCP library to be used in an android application but couldn't find any yet. As mentioned in this answer, this library doesn't provide access to RR/SR reports, even I think it doesn't even provide support for RTCP also.
Many questions I found related to RTP/RTCP were closed as off topic. Couldn't understand why.
I used https://github.com/fyhertz/libstreaming and it was working (on Android Kitkat at least), I was performing phone to phone streaming. I don't know how well it performs now.
Use