Simplify the FooterBarBehavior.

[manuel-martos]

HI @devunwired.
I've been working on merging a version that relies on offsetTopAndBottom() but no way to make it stable. I've to add some state variables and fix their values over the application life cicle and sometimes those changes aren't obious at all, making the solution really complex. That's why I'm pull requesting the simplified version that works with setTranslationY().

[devunwired]

You could achieve the same effect without adding any state tracking:

int offset = -dependency.getTop();
int newTop = parent.getBottom() - child.getHeight() + offset;
child.offsetTopAndBottom(newTop - child.getTop());
return true;

However, I looked into it a bit more and I like the simpler way just as well. It's not the code I want people focusing on in this sample repo anyway…so I'm good with it as-is.