How to create an AppBar with a bottom coloured border in Flutter?

I would like to create an App Bar like this which has a bottom border as well a tint of shadow which can be done using elevation. Could someone provide a sample code snippet to achieve this

AppBar with Border


  • Maybe something like this

       bottom: PreferredSize(
         preferredSize: const Size.fromHeight(4.0),
         child: Container(
            color: Colors.orange,
            height: 4.0,