Docked FloatingActionButton center with BottomNavigationBar

example.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: Scaffold(
        appBar: AppBar(title: Text('Title')),
        floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
        floatingActionButton:
            FloatingActionButton(child: Icon(Icons.add), onPressed: () {}),
        bottomNavigationBar: BottomAppBar(
            shape: CircularNotchedRectangle(),
            child: Container(
              height: 56,
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: <Widget>[
                  IconButton(icon: Icon(Icons.home), onPressed: () {}),
                  IconButton(icon: Icon(Icons.search), onPressed: () {}),
                  SizedBox(width: 40), // The dummy child
                  IconButton(icon: Icon(Icons.notifications), onPressed: () {}),
                  IconButton(icon: Icon(Icons.message), onPressed: () {}),
                ],
              ),
            )),
      ),
    );
  }
}