How to save SharedPreferences as an boolean flutter (problem) - flutter

Question

I try to change theme by try to use SharedPreferences to save the data. So when I reopen the app it doesn’t reset. But the problem is when I reopen the app it does reset every-time.
Please look though my code
and maybe point out what’s wrong or provide some code if you’ve already knows. Thanks
In theme:
bool? colorMode = true;
Future<bool> savebool(bool value) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.setBool("colorMode", true);
return colorMode!;
}
Future<bool> loadbool() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
prefs.getBool("colorMode")!;
return colorMode!;
}
InkWell(
child: Row(mainAxisSize: MainAxisSize.min, children: const [
SizedBox(
width: 30.0,
height: 60.0,
),
Text('- Dark Mode', style: TextStyle()),
]),
onTap: () => {
themeManager.themeMode == ThemeMode.dark,
setState(
() {
themeManager.toggleTheme(colorMode!);
colorMode = colorMode;
savebool(colorMode!);
},
),
},
),
In main (some):
ThemeManager themeManager = ThemeManager();
#override
void initState() {
themeManager.addListener(themeListener);
super.initState();
}
#override
void dispose() {
themeManager.removeListener(themeListener);
super.dispose();
}
themeListener() {
if (mounted) {
setState(() {});
}
}
MultiProvider(
providers: [
Provider(create: (_) => User),
ChangeNotifierProvider(create: (context) => themeManager)
],
child: MaterialApp(
title: 'My app',
themeMode: themeManager.themeMode,
theme: ThemeData.light(),
darkTheme: ThemeData.dark(),
home: const LoginScreen(),
debugShowCheckedModeBanner: false,
),
);
}
}

Answer 1

I think you forgot to set colorMode in loadbool() function...
Future<bool> loadbool() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
///right here, i think it must be like this
colorMode = prefs.getBool("colorMode") ?? false;
return colorMode!;
}

Answer 2

Your codes aren't full enough. I can't see the way you use save/load function. Anyway, before you get value from shared preference, you have to check it if it is null. I often load shared preferences in my singleton, like "isLogin", "firstOpenApp", "token"... Example:
DataInstance().firstLogin = prefs.getBool(PreferenceConstant.PREF_KEY_FIRST_LOGIN) ?? true;