How to add controller to streamBuilder? - flutter

Question

Flutter
Dart
I am a beginner in flutter and i am trying to add controller to streamBuilderWidget so i can dispose it but i have no idea where should i put the controller.. i tried this
the stream below as a widget not function
StreamController<QuerySnapshot> controller;
void dispose() {
super.dispose();
controller.close();
}
void initState() {
super.initState();
controller = StreamController<QuerySnapshot>();
}
StreamBuilder<QuerySnapshot>(
stream: FirebaseFirestore.instance.collection("users").doc(widget.documentUid).snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (!snapshot.hasData) {
return Center(
child: circulearProgress(),
);
}
in this code it never disposed or closed the stream:(
Anyone who edits my code in the right way will be very grateful to him , thanks friends

Answer 1

StreamController is like a pipeline. In your case, that pipeline went from water supplier to your house, there is no need to worried about what goes in there.
But if you want to set up a pipeline from your washing machine to the draining hole, that is where you need to use StreamController.
Example:
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
final NumberController controller = NumberController();
#override
void dispose() {
controller.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: SafeArea(
child: SingleChildScrollView(
child: Column(
children: [
InputWidget(controller: controller,),
OutputWidget(controller: controller,)
],
),
),
),
);
}
}
class NumberController {
//This is the pipeline of "number"
final StreamController<int> controller = StreamController<int>.broadcast();
//This is where your "number" go in
Sink<int> get inputNumber => controller.sink;
//This is where your "number" go out
Stream<int> get outputNumber => controller.stream;
//Dispose
void dispose() {
controller.close();
}
}
class InputWidget extends StatelessWidget {
final NumberController controller;
const InputWidget({Key key, this.controller}) : super(key: key);
#override
Widget build(BuildContext context) {
return InkWell(
onTap: () {
controller.inputNumber.add(Random().nextInt(10));
},
child: Text(
'Random Number'
),);
}
}
class OutputWidget extends StatelessWidget {
final NumberController controller;
const OutputWidget({Key key, this.controller}) : super(key: key);
#override
Widget build(BuildContext context) {
return StreamBuilder<int>(
stream: controller.outputNumber,
builder: (context, snapshot) {
return Text(snapshot.hasData ? snapshot.data.toString() : 'No data');
},
);
}
}

Answer 2

You don't have to use StreamController. StreamBuilder you are using closes the stream internally.

Answer 3

From your comments, you seem to want to close the listener in the method below:
void handleDelete() {
FirebaseFirestore.instance.collection("handleCountM").doc(currentUser.uid + widget.documentUid).collection("handleCountM2").limit(1).snapshots()
.listen((value) {
value.docs.forEach((element) {
element.reference.delete();
});
});
}
You can do that by getting a reference to the stream subscription and calling .cancel on the subscription.
Calling .listen on a stream returns a stream subscription object like this:
StreamSubscription handleDeleteStreamSubscription = FirebaseFirestore.instance.collection("handleCountM").doc(currentUser.uid + widget.documentUid).collection("handleCountM2").limit(1).snapshots()
.listen((value) {
value.docs.forEach((element) {
element.reference.delete();
});
});
Cancelling the subscription is done like this:
handleDeleteStreamSubscription.cancel();