Flutter Notifications show twice - flutter

Question

I have read some othe questions about this topic but I'm quite new in Flutter and I don't know how exactly I've to do in my case.
When my app is in background, the notifications are shown twice, but they have one difference. One of them has the icon I designed but the other shows the default white square icon.
This is my code:
Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
await Firebase.initializeApp();
print('Handling a background message ${message.messageId}');
flutterLocalNotificationsPlugin.show(
message.notification.hashCode,
message.notification?.title,
message.notification?.body,
NotificationDetails(
android: AndroidNotificationDetails(
channel.id,
channel.name,
channel.description,
icon: '#mipmap/icon',
),
),
);
}
const AndroidNotificationChannel channel=AndroidNotificationChannel(
'high_importance_channel',//id
'Hig Importance Notification',//name
'This channel is used', //description
importance: Importance.high,
);
final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin=FlutterLocalNotificationsPlugin();
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp(
// Replace with actual values
options: FirebaseOptions(
//apiKey: "",
apiKey: "",
appId: "",
messagingSenderId: "",
projectId: "",
storageBucket: "",
),
);
FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);
await flutterLocalNotificationsPlugin
.resolvePlatformSpecificImplementation<
AndroidFlutterLocalNotificationsPlugin>()
?.createNotificationChannel(channel);
runApp(Portada());
}
class Portada extends StatelessWidget {
const Portada({Key? key}) : super(key: key);
Widget build(BuildContext context) {
return MaterialApp(
title: "ATGapp",
home:Inicio(),
);
}
}
class Inicio extends StatefulWidget {
Inicio({Key? key}) : super(key: key);
#override
///
_InicioState createState() => _InicioState();
}
class _InicioState extends State<Inicio> {
final FirebaseMessaging _firebaseMessaging=FirebaseMessaging.instance;
#override
late StreamSubscription<User?> user;
void initState() {
getImage(path);
torneoactual();
super.initState();
var initializationSettingsAndroid=
AndroidInitializationSettings('#mipmap/icon');
var initializationSettings=
InitializationSettings(android: initializationSettingsAndroid);
flutterLocalNotificationsPlugin.initialize(initializationSettings);
FirebaseMessaging.onMessage.listen((RemoteMessage message) {
print('Handling a otro message ${message.messageId}');
RemoteNotification? notification = message.notification;
AndroidNotification? android = message.notification?.android;
if (notification != null && android != null) {
flutterLocalNotificationsPlugin.show(
notification.hashCode,
notification.title,
notification.body,
NotificationDetails(
android: AndroidNotificationDetails(
channel.id,
channel.name,
channel.description,
icon: '#mipmap/icon',
),
),
);
}
});
_firebaseMessaging.getToken().then((value) {
print(value);
tokini=value.toString();
buscatoken(tokini);
});
}
I've read something about the difference between notification and data and this is probably my problem, but I don't know how to solve it.
Than you in advance.