NavigationRail example in flutter

import 'package:flutter/material.dart';

main(List<String> args) {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  @
override

  Widget build(BuildContext context) {
    return const MaterialApp(
      home: Scaffold(
        body: MyNavigationRail(),
      ),
    );
  }
}

class MyNavigationRail extends StatefulWidget {
  const MyNavigationRail({Key? key}) : super(key: key);
  @
override

  State<MyNavigationRail> createState() => _MyNavigationRailState();
}

class _MyNavigationRailState extends State<MyNavigationRail> {
  var _selectedIndex = 0;
  @
override

  Widget build(BuildContext context) {
    return Row(
      children: [
        NavigationRail(
          destinations: const [
            NavigationRailDestination(
                icon: Icon(Icons.home), label: Text('Home')),
            NavigationRailDestination(
                icon: Icon(Icons.school), label: Text('School')),
            NavigationRailDestination(
                icon: Icon(Icons.book), label: Text('Books'))
          ],
          selectedIndex: _selectedIndex,
          onDestinationSelected: (value) {
            setState(() {
              _selectedIndex = value;
            });
          },
        ),
        Expanded(child: Center(child: Text('Selected Index: $_selectedIndex
')))
      ],
    );
  }
}