i cant switch themes with these method can you solve it? - dart

Question

static switchTheme({required ThemeBase newTheme}) {
VariableUtilities.theme = newTheme;
switch (newTheme) {
case LightTheme():
ThemeBase theme = const LightTheme();
return VariableUtilities.prefs
.setString(LocalCacheKey.applicationThemeMode, theme.toString());
case DarkTheme():
ThemeBase theme = const DarkTheme();
return VariableUtilities.prefs
.setString(LocalCacheKey.applicationThemeMode, theme.toString());
default:
ThemeBase theme = const LightTheme();
return VariableUtilities.prefs
.setString(LocalCacheKey.applicationThemeMode, theme.toString());
}
}

Answer 1

you can change theme like this. it's from flutter skeleton template.
it can change base of platform theme mode too.
main.dart
void main() async {
WidgetsFlutterBinding.ensureInitialized();
// Set up the SettingsController, which will glue user settings to multiple
// Flutter Widgets.
final settingsController = SettingsController(SettingsService());
// Load the user's preferred theme while the splash screen is displayed.
// This prevents a sudden theme change when the app is first displayed.
await settingsController.loadSettings();
// Run the app and pass in the SettingsController. The app listens to the
// SettingsController for changes, then passes it further down to the
// SettingsView.
runApp(MyApp(settingsController: settingsController));
}
class MyApp extends StatelessWidget {
const MyApp({
Key? key,
required this.settingsController,
}) : super(key: key);
final SettingsController settingsController;
#override
Widget build(BuildContext context) {
// Glue the SettingsController to the MaterialApp.
//
// The AnimatedBuilder Widget listens to the SettingsController for changes.
// Whenever the user updates their settings, the MaterialApp is rebuilt.
return AnimatedBuilder(
animation: settingsController,
builder: (BuildContext context, Widget? child) {
return MaterialApp(
debugShowCheckedModeBanner: false,
restorationScopeId: 'MyApp',
theme: AppTheme.newLightTheme(),
darkTheme: AppTheme.newDarkTheme(),
themeMode: settingsController.themeMode,
onGenerateRoute: (RouteSettings routeSettings) {
return MaterialPageRoute<void>(
settings: routeSettings,
builder: (BuildContext context) {
switch (routeSettings.name) {
case MainScreen.routeName:
return MainScreen(settingsController: settingsController);
default:
return const ChooseLogin();
}
},
);
},
);
},
);
}
}
settings_controller.dart
/// A class that many Widgets can interact with to read user settings, update
/// user settings, or listen to user settings changes.
///
/// Controllers glue Data Services to Flutter Widgets. The SettingsController
/// uses the SettingsService to store and retrieve user settings.
class SettingsController with ChangeNotifier {
SettingsController(this._settingsService);
// Make SettingsService a private variable so it is not used directly.
final SettingsService _settingsService;
// Make ThemeMode a private variable so it is not updated directly without
// also persisting the changes with the SettingsService.
late ThemeMode _themeMode;
// Allow Widgets to read the user's preferred ThemeMode.
ThemeMode get themeMode => _themeMode;
/// Load the user's settings from the SettingsService. It may load from a
/// local database or the internet. The controller only knows it can load the
/// settings from the service.
Future<void> loadSettings() async {
_themeMode = await _settingsService.themeMode();
// Important! Inform listeners a change has occurred.
notifyListeners();
}
/// Update and persist the ThemeMode based on the user's selection.
Future<void> updateThemeMode(ThemeMode? newThemeMode) async {
if (newThemeMode == null) return;
// Do not perform any work if new and old ThemeMode are identical
if (newThemeMode == _themeMode) return;
// Otherwise, store the new ThemeMode in memory
_themeMode = newThemeMode;
// Important! Inform listeners a change has occurred.
notifyListeners();
// Persist the changes to a local database or the internet using the
// SettingService.
await _settingsService.updateThemeMode(newThemeMode);
}
}
settings_services.dart
/// A service that stores and retrieves user settings.
///
/// By default, this class does not persist user settings. If you'd like to
/// persist the user settings locally, use the shared_preferences package. If
/// you'd like to store settings on a web server, use the http package.
class SettingsService {
static const String kPrefKeyThemeMode = 'ThemeMode';
/// Loads the User's preferred ThemeMode from local or remote storage.
Future<ThemeMode> themeMode() async {
SharedPreferences _prefs = await SharedPreferences.getInstance();
String _name = _prefs.getString(kPrefKeyThemeMode) ?? ThemeMode.system.name;
if (_name == ThemeMode.light.name) {
return ThemeMode.light;
} else if (_name == ThemeMode.dark.name) {
return ThemeMode.dark;
} else {
return ThemeMode.system;
}
}
/// Persists the user's preferred ThemeMode to local or remote storage.
Future<void> updateThemeMode(ThemeMode theme) async {
// Use the shared_preferences package to persist settings locally or the
// http package to persist settings over the network.
SharedPreferences _prefs = await SharedPreferences.getInstance();
_prefs.setString(kPrefKeyThemeMode, theme.name);
}
}
settings_page.dart
class SettingsPage extends StatelessWidget {
const SettingsPage({
Key? key,
required this.controller,
}) : super(key: key);
static const routeName = '/settings';
final SettingsController controller;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Settings'),
),
body: Padding(
padding: const EdgeInsets.all(16),
// Glue the SettingsController to the theme selection DropdownButton.
//
// When a user selects a theme from the dropdown list, the
// SettingsController is updated, which rebuilds the MaterialApp.
child: DropdownButton<ThemeMode>(
// Read the selected themeMode from the controller
value: controller.themeMode,
// Call the updateThemeMode method any time the user selects a theme.
onChanged: controller.updateThemeMode,
items: const [
DropdownMenuItem(
value: ThemeMode.system,
child: Text('System Theme'),
),
DropdownMenuItem(
value: ThemeMode.light,
child: Text('Light Theme'),
),
DropdownMenuItem(
value: ThemeMode.dark,
child: Text('Dark Theme'),
)
],
),
),
);
}
}