I need my toggle switch in the appBar to be visible

Question

I have created a toggle switch in the appBar but its not visible because of the code.
It changes themes between light to dark when clicked

main.dart

class MyApp extends StatelessWidget {
  static const String title = "User Profile";
    const MyApp({Key? key}) : super(key: key);

    @override
    Widget build(BuildContext context) {
      final user = UserPreferences.getUser();

      return ThemeProvider(
        initTheme: user.isDarkMode ? Mythemes.darkTheme : Mythemes.lightTheme,
        child: Builder(
          builder: (context) =>
                MaterialApp(
                debugShowCheckedModeBanner: false,
                theme: ThemeModelInheritedNotifier.of(context).theme,
                title: title,
                home: const ProfilePage(),
              ),
        ),
        );
    }
}

What do I need to change and what not to get the toggle switch visible?

themes.dart

class Mythemes {
  static const primary = Colors.blue;
  static final primaryColor = Colors.blue.shade300;

  static final darkTheme = ThemeData(
    scaffoldBackgroundColor: Colors.grey.shade900,
    primaryColorDark: primaryColor,
    dividerColor: Colors.white,
    colorScheme: const ColorScheme.dark(primary: primary).copyWith(secondary: Colors.blue),
  );
  static final lightTheme = ThemeData(
    scaffoldBackgroundColor: Colors.white,
    primaryColor: primaryColor,
    colorScheme: const ColorScheme.light(primary: primary),
    dividerColor: Colors.black,
  );
}

Appbar widget code

 AppBar buildAppBar(BuildContext context) {
  final user = UserPreferences.getUser();
  final isDarkMode = user.isDarkMode;
  final icon = isDarkMode ? CupertinoIcons.sun_max : CupertinoIcons.moon_stars;
  return AppBar(
    leading: const BackButton(
      color: Colors.blue,
    ),
    backgroundColor: Theme.of(context).scaffoldBackgroundColor,
    elevation: 0,
    actions: [
      ThemeSwitcher(
        builder: (context) => IconButton(
          color: Colors.blue,
          icon: Icon(icon),
          onPressed: () {
            final theme = isDarkMode ? Mythemes.lightTheme : Mythemes.darkTheme;
            final switcher = ThemeSwitcher.of(context);
            switcher.changeTheme(theme: theme);
            final newUser = user.copy(isDarkMode : !isDarkMode);
            UserPreferences.setUser(newUser);
          },
        ),
      ),
    ],
  );
}

how to solve this error