snack_bar.dart

import 'package:flutter/material.dart';

class MySnackBar extends StatelessWidget {
  const MySnackBar({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('SnackBar')),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            final snackBar = SnackBar(
              content: const Text('Yay! A SnackBar!'),
              action: SnackBarAction(
                label: 'Undo',
                textColor: Colors.blue,
                onPressed: () {
                  // Some code to undo the change.
                },
              ),
            );

            // Find the ScaffoldMessenger in the widget tree
            // and use it to show a SnackBar.
            ScaffoldMessenger.of(context).showSnackBar(snackBar);
          },
          child: const Text('Show SnackBar'),
        ),
      ),
    );
  }
}