How to run a function inside a child stateful widget from parent widget? - flutter

Question

I am trying to run a function(with arguments) inside two-levels down StateFul widget, by clicking a button in the parent of the parent of that child(after having all widgets built, so not inside the constructor). just like in the image below:
More details is that I created a Carousal which has Cards inside, published here.
I created it with StreamBuilder in mind(this was the only use case scenario that I used it for so far), so once the stream send an update, the builder re-create the whole Carousal, so I can pass the SELECTED_CARD_ID to it.
But now I need to trigger the selection of the carousal's Cards programmatically, or in another word no need for two construction based on the snapshot's data like this:
return StreamBuilder(
stream: userProfileBloc.userFaviourateStream,
builder: (context, snapshot) {
if (snapshot.hasData) {
return SelectableCarousal(
selectedId: snapshot.data.toInt(),
onTap: //Update the stream
//some props...,
);
} else {
return SelectableCarousalLoading(
selectedId: null,
onTap: //Update the stream
//some props...,
);
}
},
);
But instead, I'm trying to have something like this so I can use it for others use cases:
Widget myCarousal = SelectableCarousal(
selectedId: null,
onTap: //Update the stream
//some props...,
);
return StreamBuilder(
stream: userProfileBloc.userFaviourateStream,
builder: (context, snapshot) {
// Then when data ready I can update
// the selection by calling two-level down function
if (snapshot.hasData) {
myCarousal.selectById(3);
}
// Build same carousal in all cases.
return myCarousal;
},
);
so this led me to my original question "How to run a function(with arguments) inside two-levels down StateFul widget?".
I appreciate any help. thanks a lot.

Answer 1

I was able to solve that challenge using the BLoC & Stream & StreamSubscription, see the image below:
Inside the Homepage screen:
///...Inside Homepage screen level-0
RaisedButton(
child: Text('Update value in the BLoC'),
onPressed: () {
bloc.changeSelectedState(isSel);
},
),
//...
inside the BLoC:
class Bloc {
final BehaviorSubject<bool> _isSelectedStreamController = BehaviorSubject<bool>();
// Retrieve data from stream
Stream<bool> get isSelectedStream => _isSelectedStreamController.stream;
// Add data to stream
Function(bool) get changeSelectedState => _isSelectedStreamController.sink.add;
void dispose() {
_isSelectedStreamController.close();
}
}
final bloc = Bloc();
Inside any widget in any level as long as it can reach the bloc:
// This inside the two-levels down stateful widget..
StreamSubscription isSelectedSubscription;
Stream isSelectedStream = bloc.isSelectedStream;
isSelectedSubscription = isSelectedStream.listen((value) {
// Set flag then setState so can show the border.
setState(() {
isSelected = value;
});
});
//...other code
#override
Widget build(BuildContext context) {
return Container(
decoration: isSelected
? BoxDecoration(
color: Colors.deepOrangeAccent,
border: Border.all(
width: 2,
color: Colors.amber,
),
)
: null,
//...other code
);
}
so the new design of my widget includes the BLoC as a main part of it, see the image:
and...works like a charm with flexible and clean code and architecture ^^