如何在颤动中加载多个未来

Question

我正在创建一个需要从首选项设置加载电子邮件和主题的颤振应用程序。加载电子邮件将检查用户是否通过身份验证，同时加载主题将检查主题是浅色模式还是深色模式。我面临的问题是在创建界面后应用深色或浅色模式。我知道使用 future builder 可以帮助解决这个问题，但我不知道如何在 theme.dart 文件中使用它。请帮忙。

theme.dart 文件

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

CustomTheme customTheme = CustomTheme();

class CustomTheme extends ChangeNotifier {
  static bool isDarkTheme = false;

  ThemeData get currentTheme => isDarkTheme
      ? ThemeData(
          brightness: Brightness.dark,
          scaffoldBackgroundColor: Colors.grey.shade900,
          primaryColor: Colors.white,
          accentColor: Colors.blue,
          iconTheme: const IconThemeData(color: Colors.white, opacity: 0.8),
        )
      : ThemeData(
          brightness: Brightness.light,
          scaffoldBackgroundColor: Colors.white,
          primaryColor: Colors.black,
          accentColor: Colors.blue,
          iconTheme: const IconThemeData(color: Colors.black, opacity: 0.8),
          dividerColor: Colors.black12,
        );

  CustomTheme() {
    loadPrefs();
  }

  void toggleTheme() {
    isDarkTheme = !isDarkTheme;
    savePrefs();
    notifyListeners();
  }

  void savePrefs() async {
    SharedPreferences _prefs = await SharedPreferences.getInstance();
    _prefs.setBool('theme', isDarkTheme);
  }

  void loadPrefs() async {
    SharedPreferences _prefs = await SharedPreferences.getInstance();
    isDarkTheme = _prefs.getBool('theme') ?? false;
    notifyListeners();
  }
}

main.dart 文件

import 'package:chatapp/home.dart';
import 'package:chatapp/login.dart';
import 'package:chatapp/themes.dart';
import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:shared_preferences/shared_preferences.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

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

  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  Future<String> getSharedPrefs() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    String _email = prefs.getString('email') ?? '';
    return _email;
  }

  @override
  void initState() {
    super.initState();
    customTheme.addListener(() {
      setState(() {});
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: customTheme.currentTheme,
      home: FutureBuilder<String>(
        future: getSharedPrefs(),
        builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return Scaffold(
              body: Center(
                child: CircularProgressIndicator(),
              ),
            );
          } else if (snapshot.connectionState == ConnectionState.done) {
            if (snapshot.hasError) {
              return const Text('Error');
            } else if (snapshot.hasData && snapshot.data!.isNotEmpty) {
              return Home();
            } else {
              return Login();
            }
          } else {
            return Text('State: ${snapshot.connectionState}');
          }
        },
      ),
    );
  }
}

Answer 1

试试下面的代码希望它对你有帮助。使用 Future.wait([]) 方法参考here

FutureBuilder(
          future: Future.wait([
            getSharedPrefs(),
            // call your extra future method here
          ]),
          builder:
 ),