main.dart

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(
      title: 'test nav rail',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorSchemeSeed: Colors.blue,
      ),
      home: Scaffold(
      appBar: AppBar(
        title: Text('test nav rail'),
      ),
      body:        NavigationRail(
              selectedIndex : 0,
            elevation: 2,
            // to force small nav destinations to fill space
            minWidth: 105,
            // show label for all items
            groupAlignment: -1.0,
            // topAlignment
            destinations: [ 
              NavigationRailDestination(
                      padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
                      icon: Icon(Icons.info),
                      label: Text('a'),
                    ),
                 NavigationRailDestination(
                      padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
                      icon: Icon(Icons.info),
                      label: Text('b'),
                    )
            ],
            onDestinationSelected: (int index) {
              print("onDestinationSelected $index");
   
            },
          ),

    ),
    );
  }
}