Trying to make radio buttons with using Streambuilder and Bloc in Flutter. but don't work - radio-button

Question

I tried to make radiobuttons by using Streambuilder and Bloc.
so I made streamcontroler and when radiobuttons clicked,
I made streamcontrl.add(value) implemented, but Streambuilder don't listen
that stream. I tested onchanged value of radio. and
Please figure out what's wrong with it.
This is full code.
import 'package:flutter/material.dart';
import 'dart:async';
void main(){
runApp(new MaterialApp(
home: new MyApp(),
));
}
class bloc {
StreamController <int> ctrl = StreamController() ;
get blocvalue => ctrl.stream;
void setvalue (value ) {
ctrl.sink.add(value) ; }
}
class MyApp extends StatefulWidget {
#override
_State createState() => new _State();
}
class _State extends State<MyApp>{
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Name here'),
),
body: new Container(
padding: new EdgeInsets.all(15.0),
child: new Center(
child: new Column(
children: <Widget>[
StreamBuilder(
stream: bloc().blocvalue,
initialData: 0,
builder: (BuildContext context, AsyncSnapshot <int> snapshot)
{
List<Widget> list = new List<Widget>();
for(int i = 0; i < 3; i++){
list.add(new RadioListTile(
value: i,
groupValue: snapshot.data,
onChanged: bloc().setvalue,
activeColor: Colors.green,
controlAffinity: ListTileControlAffinity.trailing,
title: new Text('Item: ${i}'),
dense: true,
// subtitle: new Text('sub title'),
));
}
return Column(children: list,); })
],
),
),
),
);
}
}

Answer 1

As mentioned by pksink in the comments, you're creating a new bloc inside build by calling setting it in StreamBuilder as bloc().blocValue. What you can do here is declare it as final myBloc = bloc(); outside of the bloc and set it on your StreamBuilder as myBloc.blocValue. With this, a new instance of bloc won't be created with every rebuild of Widget build.