Flutter call Firebase Function before loading Widget - flutter

Question

I am still relatively new to Flutter and I am trying to figure out how to construct a Widget UI using external data... I have written a Firebase Function that when called generates a GetStream.io user token so that I can send that token to the Feed page of my app. I have posted my code below, it doesn't work but if someone could help it would be much appreciated.
What I am attempting to do is when this Widget initiates, set isLoading to true, call the function 'getStreamUserToken' which returns a token, once retrieved, set 'isLoading' to false and pass the token to the FeedScreen widget in the main body so that it can handle the Stream Feed.
import 'package:clubs/components/loading.dart';
import 'package:clubs/home/feed_screen.dart';
import 'package:cloud_functions/cloud_functions.dart';
import 'package:flutter/material.dart';
class ClubsApp extends StatefulWidget {
const ClubsApp({Key? key}) : super(key: key);
#override
State<ClubsApp> createState() => _ClubsAppState();
}
class _ClubsAppState extends State<ClubsApp> {
bool isLoading = false;
String? token;
void setIsLoading() {
setState(() {
isLoading = !isLoading;
});
}
#override
void initState() {
super.initState();
asyncMethod();
print('Token: ' + token!);
setIsLoading();
}
void asyncMethod() async {
token = await _getStreamToken();
}
#override
Widget build(BuildContext context) {
return isLoading
? const Loading()
: Scaffold(
body: FeedScreen(token: token!), // TODO: implement page switching
bottomNavigationBar: BottomNavigationBar(
type: BottomNavigationBarType.fixed,
items: const [
BottomNavigationBarItem(icon: Icon(Icons.home), label: "Home"),
BottomNavigationBarItem(
icon: Icon(Icons.groups_outlined), label: "Members"),
BottomNavigationBarItem(
icon: Icon(Icons.water_outlined), label: "Pontoon"),
],
selectedItemColor: const Color(0xff202441),
unselectedItemColor: const Color(0xFF02BFAB),
showUnselectedLabels: true,
),
);
}
Future<String?> _getStreamToken() async {
HttpsCallable callable =
FirebaseFunctions.instance.httpsCallable('getStreamUserToken');
final results = await callable();
String token = results.data;
return token;
}
}

Answer 1

You need to wait for asyncMethod to complete, before calling setIsLoading.
The simplest way to do that, is to hook it's then callback:
#override
void initState() {
super.initState();
asyncMethod().then((token) {
print('Token: ' + token!);
setIsLoading();
})
}
If you want to return the value, you can:
#override
void initState() {
super.initState();
return asyncMethod().then((token) {
setIsLoading();
return token;
})
}
I recommend reading up on Dart Futures and taking the Asynchronous programming: futures, async, await codelab