如何铸造未来<null>到未来<dynamic>在 Flutter 中使用flutter_local_notifications？</dynamic></null>

Question

I was working with flutter_local_notifications plugin in flutter and while initializing it I got this error.

The argument type 'Future<Null> Function(int, String, String, String)' can't be assigned to the parameter type 'Future<dynamic> Function(int, String?, String?, String?)?'

The code I am using is:

void main() async {
  SystemChrome.setEnabledSystemUIOverlays([SystemUiOverlay.bottom]);
  WidgetsFlutterBinding.ensureInitialized();

  WidgetsFlutterBinding.ensureInitialized();

  var initializationSettingsAndroid = AndroidInitializationSettings('logo');
  var initializationSettingsIOS = IOSInitializationSettings(
      requestAlertPermission: true,
      requestBadgePermission: true,
      requestSoundPermission: true,
      onDidReceiveLocalNotification:
          (int id, String title, String body, String payload) async {}),//Error on this line
          
        
  var initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid, iOS: initializationSettingsIOS);
  await flutterLocalNotificationsPlugin.initialize(initializationSettings,
      onSelectNotification: (String payload) async {
    if (payload != null) {
      debugPrint('notification payload: ' + payload);
    }
  });
  runApp(MyApp());
}

Is there a way to cast Future to Future in this function>?
Help will be really Appreciated. Thanks!

Answer 1

Seems like you are using the null safe version of that package.

With the introduction of null-safety and Nullable types you need to carefully check what parameters that the packages are providing.

The onDidReceiveLocalNotification doesn't guarantee that the title , body and payload would not be null. That is why the definition is as such inside their code,

typedef DidReceiveLocalNotificationCallback 
  = Future<dynamic> Function(int id, String? title, String? body, String? payload);

Notice the ? symbol which signifies that they are Nullable types, so you should define your callback in the same fashion.

Change your code to this,

onDidReceiveLocalNotification:
      (int id, String? title, String? body, String? payload) async {})

Answer 2

Got a Solution,Its regarding the NULL Safety in flutter
Change the error line to this:

onDidReceiveLocalNotification:
          (int id?, String title?, String body?, String payload?) async {}),//Error on this line