인프런 커뮤니티 질문&답변

제 식대로 코드를 수정했습니다.

MultiProvider로 CatService(prefs)를 호출하는 시기와 prefs를 초기화하는 시기가 비슷하여, 문제가 생겼습니다. "CatService 내부에서 async로 초기화하게 만들고
생성자에서 바로 prefs를 쓰지 않도록 수정"하는 방식을 추천하는데 그게 맞을까요? 에러 메세지는 다음과 같습니다 [ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: PlatformException(channel-error, Unable to establish connection on channel: "dev.flutter.pigeon.shared_preferences_android.SharedPreferencesApi.getAll"., null, null)

주요 코드

import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  SharedPreferences prefs = await SharedPreferences.getInstance();

  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (context) => CatService(prefs)),
      ],
      child: const MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
      theme: ThemeData(textTheme: GoogleFonts.getTextTheme('Sunflower')),
    );
  }
}

class CatService extends ChangeNotifier {
  SharedPreferences prefs;
  List<String> catImages = [];
  List<String> favoriteImages = [];

  CatService(this.prefs) {
    getRandomCatImages();
    favoriteImages = prefs.getStringList("favorites") ?? [];
  }

  void getRandomCatImages() async {
    Response result = await Dio().get(
      'https://api.thecatapi.com/v1/images/search?limit=10&mime_types=jpg',
    );
    for (var i = 0; i < result.data.length; i++) {
      catImages.add(result.data[i]["url"]);
    }
    notifyListeners();
  }

  void toggleFavoriteImages(String image) {
    if (favoriteImages.contains(image)) {
      favoriteImages.remove(image);
    } else {
      favoriteImages.add(image);
    }
    prefs.setStringList("favorites", favoriteImages);
    notifyListeners();
  }
}

<전체 코드>

import 'package:dio/dio.dart';
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  SharedPreferences prefs = await SharedPreferences.getInstance();

  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (context) => CatService(prefs)),
      ],
      child: const MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
      theme: ThemeData(textTheme: GoogleFonts.getTextTheme('Sunflower')),
    );
  }
}

class CatService extends ChangeNotifier {
  SharedPreferences prefs;
  List<String> catImages = [];
  List<String> favoriteImages = [];

  CatService(this.prefs) {
    getRandomCatImages();
    favoriteImages = prefs.getStringList("favorites") ?? [];
  }

  void getRandomCatImages() async {
    Response result = await Dio().get(
      'https://api.thecatapi.com/v1/images/search?limit=10&mime_types=jpg',
    );
    for (var i = 0; i < result.data.length; i++) {
      catImages.add(result.data[i]["url"]);
    }
    notifyListeners();
  }

  void toggleFavoriteImages(String image) {
    if (favoriteImages.contains(image)) {
      favoriteImages.remove(image);
    } else {
      favoriteImages.add(image);
    }
    prefs.setStringList("favorites", favoriteImages);
    notifyListeners();
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Consumer<CatService>(
      builder: (context, catService, child) {
        return Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.yellow,
            title: Center(child: Text("랜덤 고양이")),
            actions: [
              IconButton(
                onPressed: () {
                  Navigator.push(
                    context,
                    MaterialPageRoute(builder: (context) => FavoritePage()),
                  );
                },
                icon: Icon(Icons.favorite, color: Colors.red),
              ),
            ],
          ),
          body: SafeArea(
            child: Container(
              color: Colors.brown.shade100,
              child: GridView.count(
                crossAxisCount: 2,
                mainAxisSpacing: 8,
                crossAxisSpacing: 8,
                padding: EdgeInsets.all(8),
                children: List.generate(catService.catImages.length, (index) {
                  String catImage = catService.catImages[index];
                  return Stack(
                    children: [
                      Positioned.fill(
                        child: GestureDetector(
                          onTap: () {
                            catService.toggleFavoriteImages(catImage);
                          },
                          child: Image.network(catImage, fit: BoxFit.cover),
                        ),
                      ),
                      Positioned(
                        right: 0,
                        bottom: 0,
                        child: Icon(
                          Icons.favorite,
                          size: 40,
                          color: catService.favoriteImages.contains(catImage)
                              ? Colors.pink.shade200
                              : Colors.transparent,
                        ),
                      ),
                    ],
                  );
                }),
              ),
            ),
          ),
        );
      },
    );
  }
}

class FavoritePage extends StatelessWidget {
  const FavoritePage({super.key});

  @override
  Widget build(BuildContext context) {
    return Consumer<CatService>(
      builder: (context, catService, child) {
        return Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.yellow,
            title: Center(child: Text("좋아")),
          ),
          body: SafeArea(
            child: GridView.count(
              crossAxisCount: 2,
              mainAxisSpacing: 8,
              crossAxisSpacing: 8,
              padding: EdgeInsets.all(8),
              children: List.generate(catService.favoriteImages.length, (
                index,
              ) {
                String catImage = catService.favoriteImages[index];
                return Stack(
                  children: [
                    Positioned.fill(
                      child: GestureDetector(
                        onTap: () {
                          catService.toggleFavoriteImages(catImage);
                        },
                        child: Image.network(catImage, fit: BoxFit.cover),
                      ),
                    ),
                    Positioned(
                      right: 0,
                      bottom: 0,
                      child: Icon(
                        Icons.favorite,
                        size: 40,
                        color: catService.favoriteImages.contains(catImage)
                            ? Colors.pink.shade200
                            : Colors.transparent,
                      ),
                    ),
                  ],
                );
              }),
            ),
          ),
        );
      },
    );
  }
}