ScrollingFABBehavior

/**
 * Created by tilemachos on 7/12/15.
 */
public class ScrollingFABBehavior extends FloatingActionButton.Behavior {
    private final int toolbarHeight;

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

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

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

            }
        }
        return true;
    }
}