BottomNavigationBarItem constructor

const BottomNavigationBarItem({@required Widget icon, Widget title, Widget activeIcon, Color backgroundColor })

Creates an item that is used with BottomNavigationBar.items.

The argument icon should not be null and the argument title should not be null when used in a Material Design's BottomNavigationBar.

Implementation 

const BottomNavigationBarItem({
  @required this.icon,
  this.title,
  Widget activeIcon,
  this.backgroundColor,
}) : activeIcon = activeIcon ?? icon,
     assert(icon != null);