AppBar Scrolling Behavior

Question

We have app:layout_behavior="@string/appbar_scrolling_view_behavior"; It's work perfect for toolbar. I create custom BottomBar and wanna invert the direction of moving which causes this flag. Is there any ideas how to implement it?

Answer 1

I found solution!

We need to extend CoordinatorLayout.Behavior like this

public class BottomBarBehavior<V extends View> extends CoordinatorLayout.Behavior<V> {

    private int defaultDependencyTop = -1;

    public BottomBarBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

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

    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency) {
        if (defaultDependencyTop == -1) {
            defaultDependencyTop = dependency.getTop();
        }
        child.setTranslationY(-dependency.getTop() + defaultDependencyTop);
        return true;
    }
}

Answer 2

Eduard Poida your solution doesn't work properly when one changes the orientation of the phone while the Bottom Navigation is hidden.Screenshot

I have modified one line of your solution and it works better for me:

public class BottomNavigationBehavior<V extends View> extends CoordinatorLayout.Behavior<V>
{

private int defaultDependencyTop = -1;

public BottomNavigationBehavior(Context context, AttributeSet attrs)
{
    super(context, attrs);
}

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

@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, V child, View dependency)
{
    if (defaultDependencyTop == -1)
    {
        defaultDependencyTop = dependency.getTop();
    }
    child.setTranslationY(-dependency.getTop()*2);
    return true;
}
}