Center notched curved BottomNavigationBar

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _selectedIndex = 0;

  void _onItemTapped(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Text(
          'Selected tab: ${_selectedIndex + 1}',
          style: TextStyle(fontSize: 20),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // FAB action
        },
        shape: CircleBorder(),
        backgroundColor: Colors.teal,
        child: Icon(
          Icons.restaurant_menu,
          color: Colors.white,
        ),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
      bottomNavigationBar: ClipRRect(
        borderRadius: BorderRadius.vertical(top: Radius.circular(32)),
        child: BottomAppBar(
          shape: CircularNotchedRectangle(),
          notchMargin: 10.0,
          child: Row(
            mainAxisAlignment: MainAxisAlignment.spaceAround,
            children: [
              IconButton(
                icon: Icon(
                  Icons.home,
                  color: _selectedIndex == 0 ? Colors.teal : Colors.grey,
                ),
                onPressed: () => _onItemTapped(0),
              ),
              IconButton(
                icon: Icon(
                  Icons.search,
                  color: _selectedIndex == 1 ? Colors.teal : Colors.grey,
                ),
                onPressed: () => _onItemTapped(1),
              ),
              IconButton(
                icon: Icon(
                  Icons.notifications,
                  color: _selectedIndex == 2 ? Colors.teal : Colors.grey,
                ),
                onPressed: () => _onItemTapped(2),
              ),
              IconButton(
                icon: Icon(
                  Icons.person,
                  color: _selectedIndex == 3 ? Colors.teal : Colors.grey,
                ),
                onPressed: () => _onItemTapped(3),
              ),
            ],
          ),
        ),
      ),
    );
  }
}