Calling method in separate Class- Flutter - flutter

Question

In my main.dart at the end of a method I call 2 entities, one is within main.dart and works fine, the other is in another Class, _mapItemsExample2.
I have implemented _MyAppState(this._mapItemsExample2); functionality to call it as widget.
void main() {
SdkContext.init(IsolateOrigin.main);
runApp(MaterialApp(
theme: ThemeData(fontFamily: 'DMSans'),
home: MyApp(),
));
}
class MyApp extends StatefulWidget {
MapItemsExample2? _mapItemsExample2;
#override
_MyAppState createState() => _MyAppState(this._mapItemsExample2);
}
class _MyAppState extends State<MyApp> {
final MapItemsExample2? _mapItemsExample2;
_MyAppState(this._mapItemsExample2);
Future<void> intermodalRouter() async{
...
_sendIntermodalDataToSecondScreen(context, mappedValues, dest); //works fine
widget._mapItemsExample2?.showFirstPolylineMapMarkers(deplat, deplong, deplocname);
}
});
}
It will pass data to
class MapItemsExample2 {
void showFirstPolylineMapMarkers(deplat, deplong, deplocname) async {
print('showFirst');
...
But it goes dead and doesn't print or call _showFirstPolylineMapMarkers
I need to call the method to trigger a display of data. No errors showing but even after adding the widget function as suggested it displays nothing and doesnt print readouts
Any guidance appreciated
Thank you
Update
Recieving error in main.dart
2 positional argument(s) expected, but 0 found.
on
final MapItemsExample2 _mapItemsExample2 = MapItemsExample2();
class MapItemsExample2 {
MapItemsExample2(ShowDialogFunction2 showDialogCallback2, HereMapController hereMapController)
: _showDialog2 = showDialogCallback2,
_hereMapController = hereMapController {
void showFirstPolylineMapMarkers(deplat, deplong, deplocname) async {
print('showFirst');
Have tried adding parameters in but they are not recognised

Answer 1

You are using the ?. null-aware operator when calling showFirstPolylineMapMarkers(..), so it will only call it if widget._mapItemsExample2 is not null. Have you checked whether it is null or not at the time you're making this call?
In your code it is apparent that no instance of _mapItemsExample2 is being passed into MyApp() when you call it from main(), since the parameter list is empty. You need to create an instance of it and pass it into MyApp, or get access to a previously created instance to pass in. I don't have enough code to give you a more specific answer.