You can set the behavior of the FAB in XML.

For example:

<android.support.design.widget.FloatingActionButton    
   app:layout_behavior=".MyBehavior" />

Or you can set programmatically using:

CoordinatorLayout.LayoutParams p = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
p.setBehavior(xxxx);
fab.setLayoutParams(p);