For the earlier L Preview there were some examples like shown below to add to your code in order to use an FAB (Floating Action Button).
But unfortunately I can\'t u
Per customizing view shadows and outlines training:
You can create oval and rectangular outlines with rounded corners using the methods in the Outline class. The default outline provider for views obtains the outline from the view's background. To prevent a view from casting a shadow, set its outline provider to null.
So your ViewOutlineProvider just needs to call setOval(0, 0, size, size) on the outline parameter to getOutline():
public void getOutline (View view, Outline outline) {
// Or read size directly from the view's width/height
int size = getResources().getDimensionPixelSize(R.dimen.fab_size);
outline.setOval(0, 0, size, size);
}