[Flutter] Flutter Check Variable for Updates

I am working on a widget that holds a list view of future appointments. But the information I need is fetched with an async function. This function loads a couple of items a second but takes a while to finish. To speed up the time, I fetched the info the moment the app started.

Main Method

Future main() async {
void initAppointmentList() async {
await AppointmentList().init(30);
}
initAppointmentList();
}


Appointment List Fetching

class AppointmentList {
List<Map<String, String>> appointments = [];

Future init(int range) async {
for (int i = 0; i < range; i++) {
/*
HTTP GET Code fetching data
*/
appointments.add(/* The Data */);
}
day = day.add(const Duration(days:1));
}

}
}


Flutter Widgets

class AppointmentOverviewContainer extends StatefulWidget {
const AppointmentOverviewContainer({super.key});

@override
State<AppointmentOverviewContainer> createState() => _AppointmentOverviewContainerState();
}

class _AppointmentOverviewContainerState extends State<AppointmentOverviewContainer> {
List<Map<String, String>> appointments = AppointmentList().appointments;

@override
void initState() {
super.initState();
}

@override
Widget build(BuildContext context) {
return (/* If Appointment List Has At Least One Item Loaded */) ?
FittedBox (
fit: BoxFit.scaleDown,
child: Text(appointments[0]['Name'] ?? '',
style: GoogleFonts.lato(fontSize: 20, fontWeight: FontWeight.w500)),
) :
FittedBox (
fit: BoxFit.scaleDown,
child: Text('Loading Appointments',
style: GoogleFonts.lato(fontSize: 20, fontWeight: FontWeight.w500)),
),
);
}
}


Is there a way that the Flutter widget can check if the appointment list has been updated? If it has, display the most recent one. However, I also want it so it is able to check when the fetching has completely finished.

• 
  Since the async function was initialized in the main method, I can't use the FutureBuilder
  
  
• 
  I can't use setState because the variable updating is done externally to the widget
  
  
• 
  Putting the fetching inside of the widget prevents me from running it in the beginning
  

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