Flutter: struggle with async functions - flutter

Question

What I want to do is to load users and put them in a list. I am doing this with the function getUsers().
After that I want to load an Event (with fetchEvent()) which is a table with some dropdown menus.
My problem is that the users are sometimes not there when the event gets loaded. Thats why dropdown button is disabled.
I tried to solve this with using "then".
This is my initState:
void initState() {
besetzungsList.clear();
if (widget.eventId != null) {
getUsers().then((_) => fetchEvent());
} else
getUsers();
print(widget.eventId);
super.initState();
}
This is getUsers()
getUsers() async {
getCurrentUser();
usersStream = authBloc.getUsers();
usersStream.listen((allUsers) {
for (ApplicationUser user in allUsers) {
if (user.userRoleList.contains(team)) users.add(user.username);
}
});
}
fetchEvent() async {
...
dataTableRows.add(DataRow(
cells: [
DataCell(
Text(event.dienstMap["Aufgabe"][i]),
onTap: () {
removeRow(i);
},
),
DataCell(
Text(event.dienstMap["Zeit"][i]),
onTap: () {},
),
DataCell(
Text(event.dienstMap["Team"][i]),
onTap: () {},
),
DataCell((i > event.dienstMap["Besetzung"].length - 1 == true)
? DropDown(
hint: "Wählen",
users: users,
besetzungsListChanged: (String value) {
if (besetzungsList.length > 0) {
besetzungsList.removeAt(i);
}
besetzungsList.insert(i, value);
},
fromDropDown: (bool value) => fromDropDown = value,
)
: DropDown(
hint: event.dienstMap["Besetzung"][i],
users: users,
besetzungsListChanged: (String value) {
besetzungsList.removeAt(i);
besetzungsList.insert(i, value);
},
fromDropDown: (bool value) => fromDropDown = value,
))
],
));
}
});
setState(() {});
}

Answer 1

You can add that fetchEvent in your stream listener, so that it will get called after adding the user object to the array. Since it's a stream if you get a new user object, it will again call that fetchEvent and update your dropdown values.
Future<void> getUsers() async {
getCurrentUser();
usersStream = authBloc.getUsers();
usersStream.listen((allUsers) {
for (ApplicationUser user in allUsers) {
if (user.userRoleList.contains(team)) {
users.add(user.username);
}
}
await fetchEvent();
});
}