디렉토리 구조 [대충]

│
├── android
├── ios
├── lib
│   └── main.dart
├── test
├ ...
...

main을 갈아 엎자

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Welcome to Flutter',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Welcome to Flutter'),
        ),
        body: Center(
          child: Text('Hello World'),
        ),
      ),
    );
  }
}

첫 Flutter 앱 작성하기 - 1부