fluter使用---->动态更换Theme

create enum

enum AppTheme { Light, Dark }

final appThemeData = {
  AppTheme.Light: ThemeData(
    brightness: Brightness.light,
    textTheme: GoogleFonts.latoTextTheme(),
  ),
  AppTheme.Dark: ThemeData(
    brightness: Brightness.dark,
    textTheme: GoogleFonts.latoTextTheme(),
  ),
};

create bloc for the theme changing

• Theme state:

class AppThemeState extends Equatable {
  final AppTheme appTheme;

  AppThemeState({this.appTheme});

  @override
  List<Object> get props => [appTheme];
}

• Theme event:

abstract class AppThemeEvent extends Equatable {
  const AppThemeEvent();

  @override
  List<Object> get props => [];
}

class AppThemeChanged extends AppThemeEvent {
  final bool isLight;

  const AppThemeChanged({this.isLight});

  @override
  List<Object> get props => [isLight];
}

• Theme bloc:

class AppThemeBloc extends Bloc<AppThemeEvent, AppThemeState> {
  @override
  AppThemeState get initialState => AppThemeState(appTheme: AppTheme.Light);

  @override
  Stream<AppThemeState> mapEventToState(AppThemeEvent event) async* {
    if (event is AppThemeChanged) {
      if (event.isLight) {
        PrefsUtil.saveIsLightTheme(true);
        yield AppThemeState(appTheme: AppTheme.Light);
      } else {
        PrefsUtil.saveIsLightTheme(false);
        yield AppThemeState(appTheme: AppTheme.Dark);
      }
    }
  }
}

main screen

class _MainAppState extends State<MainApp> {
  @override
  Widget build(BuildContext context) {
    return BlocProvider<AppThemeBloc>(
      create: (context) => AppThemeBloc(),
      child: BlocBuilder<AppThemeBloc, AppThemeState>(
        builder: (BuildContext context, AppThemeState state) {
          return MaterialApp(
            home: RouterHelper.splashBuilder(context),
            theme: appThemeData[state.appTheme],
          );
        },
      ),
    );
  }
}

create the theme

BlocProvider.of<AppThemeBloc>(context).add(AppThemeChanged(isLight: !PrefsUtil.getIsLightTheme()));