How to properly initialize Stream in initState()

Question

Im trying to implement flutter package ‘Pedometer’ using this example.

Im calling provider methods from initState() in my first page loaded. Problem is pedometer listener/stream not working on initial app install, after restart everything seams working as expected.

 @override
 void initState() {
 WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
 final myProvider = Provider.of<MyProvider>(context, listen: false);
 myProvider.initPlatformState();
 });

My provider class:

class MyProvider extends ChangeNotifier {
 ...
 late Stream<StepCount> _stepCountStream;
 late Stream<PedestrianStatus> _pedestrianStatusStream;
 void initPlatformState() {
 Stream<PedestrianStatus> _pedestrianStatusStream = Pedometer.pedestrianStatusStream;
 pedestrianStatusStream
 .listen(onPedestrianStatusChanged)
 .onError(onPedestrianStatusError);
 Stream<StepCount> _stepCountStream = Pedometer.stepCountStream;
 stepCountStream.listen(onStepCount).onError(onStepCountError);
 }
}

I tried to move Stream variables into initPlatformState() but same result. I added permissions and all... Working only if i hot restart or go to other page and reload Provider.of(context, listen: false).initPlatformState();

...SO notifyListeners() not fixing issue. Im trying now with streamBuilder, where I pass stream from above, but still I got stuck at 'ConnectionState.waiting' status

Widget build(BuildContext context) {
 return Consumer<MyProvider>(builder: (context, value, child) {
 return StreamBuilder(
 stream: value.stepCountStream,
 builder: (context, snapshot) {
 if (snapshot.connectionState == ConnectionState.waiting) {
 return const Text('No data yet');
 } else if (snapshot.connectionState == ConnectionState.done) {
 return Text('Done');
 } else if (snapshot.hasError) {
 return Text('Error');
 } else {
 return Text(snapshot.data?.steps.toString() ?? '');
 }
 });
 });
 }

(until restart) so clearly something have to trigger stream?

Answer 1

try this:

class MyProvider extends ChangeNotifier {
 ...
 late Stream<StepCount> _stepCountStream;
 late Stream<PedestrianStatus> _pedestrianStatusStream;
 void initPlatformState() {
 Stream<PedestrianStatus> _pedestrianStatusStream = Pedometer.pedestrianStatusStream;
 pedestrianStatusStream
 .listen(onPedestrianStatusChanged)
 .onError(onPedestrianStatusError);
 Stream<StepCount> _stepCountStream = Pedometer.stepCountStream;
 stepCountStream.listen(onStepCount).onError(onStepCountError);
notifyListeners();
 }
}

• Alex Apps: No luck, tnx for suggestion.