In order to make it appear just call show() method on ActionButton object.
Any ScrollListeneres won't be implemented in ActionButton library because of 2 things:
This is actually not the part of the Floating Action Button library
There are many of scroll containers (not only stock android) so searching and implementing all of them is not a trivial task and indeed it is simpler to call show() and hide() instead of making all this stuff
I want the fab to appear only when scrolling