import 'package:flutter/material.dart';void main() { runApp(MyApp());}class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( // 앱 바 theme: ThemeData( appBarTheme: AppBarTheme( backgroundColor: Colors.blue, elevation: 0, shape: Border(bottom: BorderSide(color: Colors.black, width: 2)), ), ..