Trouble rebuilding a StreamProvider to update its current data - flutter

Question

so I have aConsumer<NotificationProvider> and in its builder function a StreamProvider<List<Item>>.
Please note that the latter widget builds perfectly on its initial load.
NotificationProvider contains a list of notifications from Firebase Cloud Messaging, ergo when I receive a notification, I push something into the class' Listand then callnotifyListeners()`.
Please also note that my NotificationProvider is doing a good job because I have a counter at my AppBar and it's updating whenever I receive one.
Now on to the meat and potato.
I'm trying to rebuild the StreamProvider whenever NotificationProvider.addAlert() is called. But somehow it's not working?
I also added updateShouldNotify: (prev, next) => true, but it didn't help one bit.
Please help. Thanks!
I also added updateShouldNotify: (prev, next) => true, on the StreamProvider properties but it didn't help one bit.
return Consumer<NotificationProvider>(
builder: (context, provider, child) {
return StreamProvider<ItemsProvider>(
builder: (_) async* {
ItemsProvider _itemsProvider = Provider.of<ItemsProvider>(context);
await _itemsProvider.getItems();
yield _itemsProvider;
},
child: LeContent(),
updateShouldNotify: (prev, next) => true,
);
},
);
I expect the list to update whenever I receive an FCM notification

Answer 1

The builder parameter is called exactly once for the entire life of the StreamProvider.
The fact that you called Provider.of<ItemsProvider> doesn't change anything here – the method still won't be called again, even if ItemsProvider changes.
If you insist in using StreamProvider, you'll need to somehow transform the Provider.of into a stream instead.
You can use a StatefulWidget to do so. Here's an example:
class ProviderToStream<T> extends StatefulWidget {
const ProviderToStream({Key key, this.builder, this.child}) : super(key: key);
final ValueWidgetBuilder<Stream<T>> builder;
final Widget child;
#override
_ProviderToStreamState<T> createState() => _ProviderToStreamState<T>();
}
class _ProviderToStreamState<T> extends State<ProviderToStream> {
final StreamController<T> controller = StreamController<T>();
#override
void dispose() {
controller.close();
super.dispose();
}
#override
void didChangeDependencies() {
super.didChangeDependencies();
controller.add(Provider.of<T>(context));
}
#override
Widget build(BuildContext context) {
return widget.builder(context, controller.stream, widget.child);
}
}
You can then do:
ProviderToStream<Foo>(
builder: (_, stream, __) {
return StreamProvider(
builder: (_) async* {
await for (final value in stream) {
// TODO: yield something
}
}
);
}
)

Answer 2

I solved my own issue by having a StreamBuilder in a StatefulWidget.
I have my fetcher as a separate Future<T> method which will be called on initState and on didUpdateWidget().
Next, in my StatefulWidget class, I require something that will be used to validate on didUpdateWidget()'s oldWidget.something != widget.something.
In my case I used the length of the NoticeProvider.notices which will be incremented every time my FCM configuration triggers it.
in code:
#override
void didUpdateWidget(_Body oldWidget) {
if (oldWidget.alertLength != widget.alertLength) _fetchData();
super.didUpdateWidget(oldWidget);
}
_fetchData, will then call the api, transform the JSON, and add it to the stream using a StreamController which, in turn, update the UI.
I hope someone will be helped by this answer in the Future!