fix: theme was not persistant

Now using shared prefs for persistant storage and riverpod to maintain the state of the theme

Author: prathameshkhade

lib/main.dart

@@ -3,46 +3,63 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:sysadmin/core/theme/app_theme.dart';
 import 'package:sysadmin/presentation/screens/dashboard/index.dart';
-import 'package:sysadmin/providers/theme_provider.dart';
 import 'package:sysadmin/presentation/screens/onboarding/index.dart';
+import 'package:sysadmin/providers/theme_provider.dart';
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
   final prefs = await SharedPreferences.getInstance();
   final bool isOnBoardingDone = prefs.getBool('isOnBoardingDone') ?? false;
   runApp(
       ProviderScope(
-          child: SysAdminMaterialApp(isOnBoardingDone: isOnBoardingDone)
+          child: SysAdminMaterialApp(
+            isOnBoardingDone: isOnBoardingDone,
+          )
       )
   );
 }
 
 // Returns Material App
 class SysAdminMaterialApp extends ConsumerWidget {
-   final bool isOnBoardingDone;
+  final bool isOnBoardingDone;
 
-   const SysAdminMaterialApp({
+  const SysAdminMaterialApp({
     super.key,
     this.isOnBoardingDone = false,
   });
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
-    final isDark = ref.watch(themeProvider);
-
-    return MaterialApp(
-      debugShowCheckedModeBanner: false,
-      theme: AppTheme.lightTheme,
-      darkTheme: AppTheme.darkTheme,
-      themeMode: isDark ? ThemeMode.dark : ThemeMode.light,
-      title: 'SysAdmin',
-      home: SysAdminApp(isOnBoardingDone: isOnBoardingDone),
+    final isDarkTheme = ref.watch(themeProvider);
+    final initialThemeAsync = ref.watch(initialThemeProvider);
+
+    return initialThemeAsync.when(
+      data: (_) => MaterialApp(
+        debugShowCheckedModeBanner: false,
+        theme: AppTheme.lightTheme,
+        darkTheme: AppTheme.darkTheme,
+        themeMode: isDarkTheme ? ThemeMode.dark : ThemeMode.light,
+        title: 'SysAdmin',
+        home: SysAdminApp(isOnBoardingDone: isOnBoardingDone),
+      ),
+      loading: () => const MaterialApp(
+        home: Scaffold(
+          body: Center(
+            child: CircularProgressIndicator(),
+          ),
+        ),
+      ),
+      error: (error, stack) => MaterialApp(
+        home: Scaffold(
+          body: Center(
+            child: Text('Error loading theme: $error'),
+          ),
+        ),
+      ),
     );
   }
-
 }
 
-// Returns Scaffold
 class SysAdminApp extends StatelessWidget {
   final bool isOnBoardingDone;
 
@@ -53,11 +70,10 @@ class SysAdminApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-
-    return  Scaffold(
+    return Scaffold(
       body: Center(
         child: isOnBoardingDone ? const DashboardScreen() : const OnBoarding(),
       ),
     );
   }
-}
+}

lib/providers/theme_provider.dart

@@ -1,13 +1,25 @@
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
+// Provider to get the initial theme value
+final initialThemeProvider = FutureProvider<bool>((ref) async {
+  final prefs = await SharedPreferences.getInstance();
+  return prefs.getBool('isDark') ?? false;
+});
+
+// Theme state provider
 final themeProvider = StateNotifierProvider<ThemeNotifier, bool>((ref) {
-  return ThemeNotifier();
+  // Get the initial value synchronously, fall back to false if not loaded yet
+  final initialTheme = ref.watch(initialThemeProvider).value ?? false;
+  return ThemeNotifier(initialTheme);
 });
 
 class ThemeNotifier extends StateNotifier<bool> {
-  ThemeNotifier() : super(false); // Start with light theme
+  ThemeNotifier(super.initialState);
 
-  void toggleTheme() {
+  void toggleTheme() async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool('isDark', !state);
     state = !state;
   }
 }