flutter - 如何在 flutter 朔迷离的共享首选项中存储主题

在这里，我有一个屏幕，当我按下该按钮时，我会有一些按钮，它将改变应用程序的颜色，但是当我重新启动应用程序时，它将重置。我希望它不会重置，直到我从应用程序更改颜色。因此，我想将THemedata存储在共享首选项中，并且希望从共享首选项中获取主题数据，因此，每当我重新启动应用程序时，都需要从共享首选项中获取主题。

这是我尝试过的一些代码，

ThemeBloc.dart

class ThemeBloc extends Bloc<ThemeEvent, ThemeState> {
  @override
  ThemeState get initialState =>
      ThemeState(themeData: appThemeData[AppTheme.GreenLight]);

  @override
  Stream<ThemeState> mapEventToState(
    ThemeEvent event,
  ) async* {
    if (event is ThemeChanged) {
      yield ThemeState(themeData: appThemeData[event.theme]);
    }
  }
}

ThemeEvent.dart

abstract class ThemeEvent extends Equatable {
  ThemeEvent([List props = const <dynamic>[]]) : super(props);
}

class ThemeChanged extends ThemeEvent {
  final AppTheme theme;

  ThemeChanged({
    this.theme,
  }) : super([theme]);
}

ThemeState.dart

@immutable
class ThemeState extends Equatable {
  final ThemeData themeData;

  ThemeState({
    @required this.themeData,
  }) : super([themeData]);
}

AppTheme.dart

enum AppTheme {
  GreenLight,
  GreenDark,
  BlueLight,
  BlueGrey,
  Amber,
}

final appThemeData = {
  AppTheme.GreenLight: ThemeData(
    brightness: Brightness.light,
    primaryColor: Colors.teal,
  ),
  AppTheme.GreenDark: ThemeData(
    brightness: Brightness.light,
    primaryColor: Colors.orange,
  ),
};

最佳答案

您可以简单地保存/获取主题ID，该ID可用于识别启动应用程序时选择的主题，例如

class ThemeBloc extends Bloc<ThemeEvent, ThemeState> {

  // at this point you should be already have a mainSharedPreferences already initialized, could be in SplashScreen
  // to prevent async calls in the initialState

  @override
  ThemeState get initialState => ThemeState(
      themeData: appThemeData[
          MyApp.mainSharedPreferences.getInt("selectedThemeIndex") ??
              AppTheme.GreenLight]);

  @override
  Stream<ThemeState> mapEventToState(
    ThemeEvent event,
  ) async* {
    if (event is ThemeChanged) {
      await _persistTheme(event.theme);
      yield ThemeState(themeData: appThemeData[event.theme]);
    }
  }

  _persistTheme(AppTheme theme) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setInt("selectedThemeIndex", theme.index);
    // or you could save the theme.toString()
    // prefs.setString("selectedTheme", theme.toString());
  }
}

如何准备SharedPreferences以避免Future<SharedPreferences>

class MyApp extends StatefulWidget {
  static SharedPreferences mainSharedPreferences;

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



class _MyAppState extends State<MyApp> {

_loadApp() async {
    MyApp.mainSharedPreferences = await SharedPreferences.getInstance();
    // you can load here any other data or external data that your app might need
  }

  @override
  void initState() {
    super.initState();
    _loadApp();
  }

@override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      localizationsDelegates: [
      // ...

然后，您可以在应用程序中的任何地方使用它，就像这样

// to save value
MyApp.mainSharedPreferences.setInt("selectedThemeIndex", value);

// to get the saved value
MyApp.mainSharedPreferences.getInt("selectedThemeIndex");

关于flutter - 如何在 flutter 朔迷离的共享首选项中存储主题，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/59841810/