Singleton doesn't have unique instance Flutter - flutter

Question

I'm trying to implement the singleton pattern with null safety in Flutter, to do a unique instance for my sqflite database, but after initialization in the splashScreen, when I try to access it in another Widget, it seems that it's not the same instance since the database is not initialized. I tried to add a random() int to check if it has the same value in the different widget, and the value change each times I request it.
My code is like this :
class DatabaseHandler {
final int random = new Random().nextInt(200);
static final DatabaseHandler instance = new DatabaseHandler._internal();
factory DatabaseHandler() {
return instance;
}
DatabaseHandler._internal();
late Database _database;
Database getDb() {
print(random);
return _database;
}
Future<void> initDB() async {
var path = await getDatabasesPath();
var dbPath = join(path, 'test.db');
Database dbConnection = await openDatabase(dbPath, version: 1,
onCreate: (Database db, int version) async {
return db.execute(
"CREATE TABLE favorite_page(id TEXT PRIMARY KEY, isFavorite BOOL)",
);
});
this._database = dbConnection;
}
}
I got a "Not initialize exception" when I do getDb() even if I used initDB() in the splashScreen.
I call the singleton in two places :
The db is initialized here :
class _SplashPageState extends State<SplashPage> {
static const String route = "/splash";
void initializeFlutterFire() async {
// Wait for Firebase to initialize and set `_initialized` state to true
await Firebase.initializeApp();
PushNotificationService pushNotif = PushNotificationService();
pushNotif.initialise();
}
#override
initState() {
super.initState();
WidgetsFlutterBinding.ensureInitialized();
initializeFlutterFire();
DatabaseHandler().initDB();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Lottie.asset('assets/lotties/loading-screen.json',
animate: true, repeat: true)));
}
}
and used here :
class PagesDb {
Future<FavoritePage> insert(FavoritePage page) async {
var db = DatabaseHandler().getDb();
await db.insert(tablePage, page.toMap());
return page;
}
}
But I tried to just use DatabaseHandler().getDb() in different widgets, they got the same random value, but not the same as in the splash screen