In the past, a JavaFX Application could be linked to an Android Activity via the FXActivity.
There were requests to also support Android Fragments, in a way that a JavaFX application can be used as an Android Fragment, allowing for a hybrid application.
This has been done in javafxports, and it requires a few changes that shouldn't affect the other platforms.

1. Alter the existing FXActivity and Launcher classes:
https://bitbucket.org/javafxports/8u60-rt/commits/c3f73046d5782ddf3f7ee1614cf46bbeae422289

Note that this patch also contains a few modifications to the buildSrc/dalvik.gradle that are not related to this particular issue.

2. Add the new DalvikEntity and the FXFragment class
https://bitbucket.org/javafxports/8u60-rt/commits/15d62d510f9dbc89c08eafc171ddb38f4bc3ac07

3. Change the native activity.c file, add activity.h in order to call into DalvikEntity instead of FXActivity
https://bitbucket.org/javafxports/8u60-rt/commits/4914006cbd5a601726035c231321eb759a7bc9e2