Async Listview update in flutter - flutter

Question

I have created a program which displays a list view in build method and in init I have a async method.
That async method after 3 seconds adds an element in list and try to set State.
It is not working. My code is as follows.
calling async function in init may be wrong, i want to show the List view then make an async http call and then update the list view. and this should work even after push and pop.
import 'dart:async';
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
List<String> europeanCountries = [
'Albania',
'Andorra',
'Armenia',
'Austria',
'Azerbaijan',
'Belarus',
'Belgium',
'Bosnia and Herzegovina'
];
int _counter = 0;
void _incrementCounter() async {
const ThreeSec = const Duration(seconds: 3);
Timer(ThreeSec, () {
europeanCountries.insert(0, "Testing");
print(europeanCountries);
});
setState(() {
_counter++;
});
}
#override
void initState() {
// TODO: implement initState
super.initState();
_incrementCounter();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: _myListView(context),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
Widget _myListView(BuildContext context) {
// backing data
return ListView.builder(
itemCount: europeanCountries.length,
reverse: true,
itemBuilder: (context, index) {
return ListTile(
title: Text(europeanCountries[index]),
);
},
);
}
}

Answer 1

Use timeout method handle and call setState method inside that method like following way
Timer(ThreeSec, () {
europeanCountries.insert(0, "Testing");
print(europeanCountries);
setState(() {
_counter++;
});
});