libGDX
Desktop/Android/HTML5/iOS Java game development framework
...Publish your games on Windows, macOS, Linux (including the RPi!), Android, iOS, and HTML5, all with the same code base. libGDX comes with batteries included. Write 2D or 3D games and let libGDX worry about low-level details. Heavy emphasis is put on avoiding garbage collection for ART/JavaScript by careful API design and the use of custom collections. libGDX is a well proven and reliable framework with a sound base and documentation. Furthermore, there are plenty of games built on top of libGDX, many of which are open source.