Stream Builder with HTTP request is not working [Flutter] - flutter

Question

I tried for the first time using Stream builder with HTTP requests. it is not updating data.
find below my code. Thanks for helping me!
///////////////////////////////////////// ////////////////////////////////// /////////////// //////////////////// ///////////////////// //////////////////// ///////////////////////////
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner:false,
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({ Key? key }) : super(key: key);
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: StreamBuilder(
stream: listMarkers,
builder: (BuildContext context,AsyncSnapshot<List<Coordonnees>> snapshot){
switch (snapshot.connectionState){
case ConnectionState.none:
// TODO: Handle this case.
// break;
case ConnectionState.waiting:
// TODO: Handle this case.
// break;
case ConnectionState.active:
return Center(child:CircularProgressIndicator());
// break;
case ConnectionState.done:
List<Coordonnees>? mark=snapshot.data;
return Center(
child:Text('latitude: ${mark![0].latitude}',
style: TextStyle(
fontSize: 30,
)
),
);
// break;
}
},
),
);
}
List<Coordonnees> marqueurs=[];
Future<List<Coordonnees>> UpdateMarkers(String id) async{
Map data = {
'idligne': id,
};
final response = await http.post(
Uri.parse("https://www.sirius-iot.eu/Dev/ESI/qitari2021/sarah.php?lignegps"),
body: data);
Map<String,dynamic> map=json.decode(response.body);
List<dynamic> dataa = map['lignegps'];
marqueurs.clear();
for(var i in dataa)
{
Coordonnees crd=Coordonnees(double.parse(i['latitude']),double.parse(i['longitude']),double.parse(i['vitesse']));
marqueurs.add(crd);
}
return marqueurs;
}
Stream<List<Coordonnees>> get listMarkers async*{
String id='1';
yield await UpdateMarkers(id) ;
}
}
class Coordonnees{
double latitude;
double longitude;
double vitesse;
Coordonnees(this.latitude,this.longitude,this.vitesse);
}

Answer 1

You can try .asStream() instead of manually yielding data which is awaited.
void main() {
listMarkers.listen((coordinates) {
print(coordinates);
});
}
class Coordinates {
int x;
int y;
Coordinates(this.x, this.y);
}
Future<List<Coordinates>> updateMarkers(String id) async{
await Future.delayed(Duration(seconds: 2));
return [
Coordinates(1,2)
];
}
Stream<List<Coordinates>> get listMarkers => updateMarkers('1').asStream();
Notice how elegant Stream<List<Coordinates>> get listMarkers => updateMarkers('1').asStream(); is as compared to what you are doing. And hopefully it will solve your issue too.