SudokuFX is a sudoku game built using JavaFX library, which can be exported to an android apk using the javafxports gradle plugin.
$ gradle android
Javafxports gradle plugin: http://javafxports.org/
Sudoku generator algorithm is based on the work of team FUXIA: https://github.com/mihneagiurgea/fuxia
Digging algorithm developed and described by ZHANGroup: http://zhangroup.aporc.org/images/files/Paper_3485.pdf