How to wait for Streambuilder to return a value before coming off a loading screen - flutter

Question

Question
I have an app that loads a list of habits as a Stream from Firestore, and I want the app to show a loading screen until habit loading has completed, and then show the list if there is one. Is there a way to keep a loading screen showing until we've either finished loading the first value in the stream or determined there won't be one?
The issue I'm having is that while my app is showing the loading screen, it briefly loads with a "no habits found" view before switching to show the list of habits.
Setup
This view uses three components:
I have a model-view-viewmodel architecture based on the Stacked Package.
(1) My view is a ViewModelBuilder widget with a StreamBuilder inside it. It looks at a (2) DailyViewModel, where the relevant components are an isBusy boolean property and a Stream<List<HabitCompletionViewModel> property that the view's StreamBuilder looks at to display the habits. The habits are loaded from Firestore via a FirestoreHabitService (this is an asynchronous call - will be described in a minute).
The View works as follows:
If DailyViewModel.isBusy is true, show a Loading... text.
If isBusy is false, it will show a Stream of Habits, or the text "No Habits Found" if the stream is not returning any habits (either snapshot.hasData is false, or data.length is less than 1).
#override
Widget build(BuildContext context) {
return ViewModelBuilder.reactive(
viewModelBuilder: () => vm,
disposeViewModel: false,
builder: (context, DailyViewModel vm, child) => vm.isBusy
? Center(child: Text('Loading...'))
: SingleChildScrollView(
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
'BaseDate of ${DateFormat.yMd().format(vm.week.baseDate)}'),
Text(
'Week ${DateFormat.yMd().format(vm.week.beginningOfWeek)} - ${DateFormat.yMd().format(vm.week.endOfWeek)}'),
SizedBox(height: 20),
Row(
children: [
Flexible(
child: Text('Today',
style: Theme.of(context).textTheme.headline6),
),
],
),
const Padding(padding: EdgeInsets.all(2)),
StreamBuilder<List<HabitCompletionViewModel>>(
stream: vm.todaysHabits,
builder: ((context, snapshot) {
if (snapshot.hasData == false ||
snapshot.data == null ||
snapshot.data!.length < 1) {
return Center(child: Text('No Habits Found'));
} else {
return Column(children: [
ListView.builder(
scrollDirection: Axis.vertical,
shrinkWrap: true,
itemCount: snapshot.data!.length,
itemBuilder: (context, i) => HabitCompletionTile(
key: ValueKey(snapshot.data![i].habit.id),
vm: snapshot.data![i],
),
),
]);
}
})),
SizedBox(height: 40),
TextButton(
child: Text('Create a New Habit'),
onPressed: () => vm.navigateToCreateHabitPage(),
),
],
),
),
);
}
}
Process of Loading the Data
My loading happens as follows:
The ViewModel is initialized, and setBusy is set to true.
DailyViewModel({required WeekDates week}) {
setBusy(true);
_log.v('initializing the daily viewmodel');
pageSubtitle =
'Week of ${week.startWeekday.title} ${DateFormat.Md().format(week.beginningOfWeek)}';
_log.v('page subtitle is $pageSubtitle');
mainAsyncCode();
}
Then it starts this mainAsyncCode() method, which gets a stream of habits from the FirestoreHabitService (this returns a Future<Stream<List<Habit>>> because there is a potential modification function performed on the habits before returning them), and once that is completed, transforms that stream into a Stream<List<HabitCompletionViewModel>>, and then sets isBusy on the ViewModel to false.
void mainAsyncCode() async {
_myHabits = await _habitService.loadActiveHabitsByUserFuture(_loginAndUserService.loggedInUser!.id!);
todaysHabits = _myHabits!.transform(currentViewModelCompletion);
await Future.delayed(Duration(seconds: 5));
setBusy(false);
}
Issue
The problem is that there is a temporary delay where the screen goes from "Loading..." to "No Habits Found" before it shows the list of Habits. I want it to wait on "Loading" until the stream list has been published, but I can't think of a way to do that.
Are there any options for doing this that others are aware of?