My goal is to create an app where the user can choose his preferred theme. I'm saving the user's choice with shared preferences so I can load it the next app start. The user can either select: - Dark Mode (Independent from the OS Settings) - Light Mode (Independent from the OS Settings) - System (Changes between Dark Mode and Light mode depending on the OS settings) With the help of BLoC, I almost achieved what I want. But the problem is that I need to pass the brightness inside my Bloc event. And to get the system (OS) brightness I need to make use of
MediaQuery.of(context).platformBrightness
But the Bloc gets initiated before MaterialApp so that MediaQuery is unavailable. Sure I can pass the brightness later(from a child widget of MaterialApp) but then (for example, if the user has dark mode activated) it goes from light to dark but visible for a really short time for the user(Because inside the InitialState I passed in light mode).
class MyApp extends StatelessWidget {
final RecipeRepository recipeRepository;
MyApp({Key key, @required this.recipeRepository})
: assert(recipeRepository != null),
super(key: key);
@override
Widget build(BuildContext context) {
return MultiBlocProvider(
providers: [
BlocProvider<ThemeBloc>(create: (context) =>
ThemeBloc(),),
],
child: BlocBuilder<ThemeBloc, ThemeState>(
builder: (context, state){
return MaterialApp(
theme: state.themeData,
title: 'Flutter Weather',
localizationsDelegates: [
FlutterI18nDelegate(fallbackFile: 'en',),
GlobalMaterialLocalizations.delegate,
GlobalWidgetsLocalizations.delegate
],
supportedLocales: [
const Locale("en"),
const Locale("de"),
],
home: Home(recipeRepository: recipeRepository),
);
},
),
);
}
}
ThemeBloc:
class ThemeBloc extends Bloc<ThemeEvent, ThemeState> {
@override
ThemeState get initialState =>
ThemeState(themeData: appThemeData[AppTheme.Bright]);
@override
Stream<ThemeState> mapEventToState(
ThemeEvent event,
) async* {
if (event is LoadLastTheme) {
ThemeData themeData = await _loadLastTheme(event.brightness);
yield ThemeState(themeData: themeData);
}
if (event is ThemeChanged) {
await _saveAppTheme(event.theme);
yield ThemeState(themeData: appThemeData[event.theme]);
}
}
Future<ThemeData> _loadLastTheme(Brightness brightness) async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
String themeString = prefs.getString(SharedPrefKeys.appThemeKey);
print("saved theme: $themeString");
if ((prefs.getString(SharedPrefKeys.appThemeKey) != null) &&
themeString != "AppTheme.System") {
switch (themeString) {
case "AppTheme.Bright":
{
return appThemeData[AppTheme.Bright];
}
break;
///Selected dark mode
case "AppTheme.Dark":
{
return appThemeData[AppTheme.Dark];
}
break;
}
}
print("brightness: $brightness");
if (brightness == Brightness.dark) {
return appThemeData[AppTheme.Dark];
} else {
return appThemeData[AppTheme.Bright];
}
}
Future<void> _saveAppTheme(AppTheme appTheme) async {
final SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setString(SharedPrefKeys.appThemeKey, appTheme.toString());
}
}