import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(useMaterial3: true),
      home: const NavRailExample(),
    );
  }
}

class NavRailExample extends StatefulWidget {
  const NavRailExample({super.key});

  @override
  State<NavRailExample> createState() => _NavRailExampleState();
}

class _NavRailExampleState extends State<NavRailExample> {
  int _selectedIndex = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Row(
        children: <Widget>[
          NavigationRail(
            extended: true,
            selectedIndex: _selectedIndex,
            onDestinationSelected: (int index) {
              setState(() {
                _selectedIndex = index;
              });
            },
            destinations: const <NavigationRailDestination>[
              NavigationRailDestination(
                icon: Icon(Icons.favorite_border),
                selectedIcon: Icon(Icons.favorite),
                label: Text('First'),
              ),
              NavigationRailDestination(
                icon: Icon(Icons.bookmark_border),
                selectedIcon: Icon(Icons.book),
                label: Text('Second'),
              ),
              NavigationRailDestination(
                icon: Icon(Icons.star_border),
                selectedIcon: Icon(Icons.star),
                label: Text('Third'),
              ),
            ],
          ),
          const VerticalDivider(thickness: 1, width: 1),
          // This is the main content.
            Expanded(
              child: Container(),
            ),
        ],
      ),
    );
  }
}