HideOnScrollExample - custom fab behavior

ScrollingFABBehavior.java

public class ScrollingFABBehavior extends CoordinatorLayout.Behavior<FloatingActionButton> {
    private int toolbarHeight;

    public ScrollingFABBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.toolbarHeight = Utils.getToolbarHeight(context);
    }

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
        return dependency instanceof AppBarLayout;
    }

    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
        if (dependency instanceof AppBarLayout) {
                CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
                int fabBottomMargin = lp.bottomMargin;
                int distanceToScroll = fab.getHeight() + fabBottomMargin;
                float ratio = (float)dependency.getY()/(float)toolbarHeight;
                fab.setTranslationY(-distanceToScroll * ratio);
        }
        return true;
    }
}