🚀 Flutter Challenges: Problem 1

01-spot-the-error.dart

import 'package:flutter/material.dart';

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

class UserService {
  static const _dummyUsers = ['John', 'Mike', 'Jill', 'Steve'];

  Future<List<String>> getUsers() async {
    await Future<void>.delayed(const Duration(seconds: 5));
    return _dummyUsers;
  }
}

class MyApp extends StatelessWidget {
  static final userService = UserService();

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: '🚀 Flutter Challenges',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomePage(),
      routes: {
        '/second': (_) => SecondPage(userService),
      },
    );
  }
}

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('🚀 Flutter Challenges'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('Go to Users'),
          onPressed: () {
            Navigator.of(context).pushNamed('/second');
          },
        ),
      ),
    );
  }
}

class SecondPage extends StatefulWidget {
  final UserService userService;

  SecondPage(this.userService);

  @override
  State<SecondPage> createState() => _SecondPageState();
}

class _SecondPageState extends State<SecondPage> {
  List<String> _users;

  @override
  void initState() {
    super.initState();
    widget.userService.getUsers().then((users) {
      setState(() => _users = users);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('🚀 Flutter Challenges'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            if (_users == null) ...const [
              Text('Loading users...'),
              SizedBox(height: 20),
              CircularProgressIndicator(),
            ] else
              ..._users.map((user) => Text(user)),
            const SizedBox(height: 20),
            RaisedButton(
              child: const Text('Back'),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          ],
        ),
      ),
    );
  }
}