Way of use with PageView and sliding animation from example.gif you can see in example folder.
Attributes
items: List of Widgets
initialIndex: Initial index of Curve
color: Color of NavigationBar, default Colors.white
defaultBubbleColor: background color of floating bubble
onTap: Function handling taps on items
animationCurve: Curves interpolating button change animation, default Curves.easeInOutQuad
animationDuration: Duration of button change animation, default Duration(milliseconds: 500)