플러터 순한맛 강좌 - 플러터 2.0 스낵바(Snack bar)와 ScaffoldMessenger

다음 코드는 코딩셰프의 코드를 참고하여 작성하였습니다.
완전 초보용 플러터(flutter) 26: 패치 강좌 1 | 플러터 2.0 스낵바(Snack bar)와 ScaffoldMessenger

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Scaffold Messenger',
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      home: MyPage(),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Scaffold Messenger'),
      ),
      body: HomeBody(),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.thumb_up),
        onPressed: () {
          ScaffoldMessenger.of(context).showSnackBar(
            // 가장 가까운 Scaffold를 찾아서 반환하라는 의미
            SnackBar(
              content: Text('Like a new Snack bar!'),
              duration: Duration(seconds: 5),
              action: SnackBarAction(
                label: 'Undo',
                onPressed: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(builder: (context) => ThirdPage()),
                  );
                },
              ),
            ),
          );
        },
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Center(
      child: ElevatedButton(
        child: Text('Go to the second page'),
        onPressed: () {
          Navigator.push(
            context,
            MaterialPageRoute(builder: (context) => SecondPage()),
          );
        },
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Second Page'),
      ),
      body: Center(
        child: Text(
          '좋아요가 추가되었습니다.',
          style: TextStyle(
            fontSize: 20.0,
            color: Colors.redAccent,
          ),
        ),
      ),
    );
  }
}

class ThirdPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ScaffoldMessenger(
      child: Scaffold(
        appBar: AppBar(
          title: Text('Third Page'),
        ),
        body: Builder(
          builder: (context) {
            return Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Text(
                    '좋아요를 취소하시겠습니까?.',
                    style: TextStyle(
                      fontSize: 20.0,
                      color: Colors.redAccent,
                    ),
                  ),
                  ElevatedButton(
                      onPressed: () {
                        ScaffoldMessenger.of(context).showSnackBar(
                          SnackBar(
                            content: Text('좋아요가 취소되었습니다.'),
                            duration: Duration(seconds: 3),
                          ),
                        );
                      },
                      child: Text('취소하기'))
                ],
              ),
            );
          }
        ),
      ),
    );
  }
}