RangeError (index): Valid value range is empty: 0 - flutter

Question

I am trying to display data from an api in a ListView.builder, I want to set the itemCount to 20 but when I do that, before the data is displayed I get the following error RangeError (index): Valid value range is empty: 0 the '0' is incremented in each card until '20'. If anyone can help me, thanks.
import 'dart:typed_data';
import 'package:badges/badges.dart';
import 'package:banner_carousel/banner_carousel.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:kaomini/Pages/accueil.dart';
import 'package:kaomini/Pages/detail_article.dart';
import 'package:kaomini/Pages/panier.dart';
import 'package:kaomini/widgets/drawer_menu.dart';
import 'package:kaomini/widgets/images.dart';
class PromoArticle extends StatefulWidget {
const PromoArticle({Key? key}) : super(key: key);
_PromoArticleState createState() => _PromoArticleState();
}
class _PromoArticleState extends State<PromoArticle> {
List userdata = [];
int _count = 20;
Future<void> getrecord() async {
var uri = Uri.parse(
My api;
try {
var response = await http.get(
uri,
);
setState(() {
userdata = jsonDecode(response.body);
});
} catch (e) {
print(e);
}
}
void increment(){
setState((){
_count = _count + 10;
});
}
#override
void initState() {
getrecord();
super.initState();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
iconTheme: const IconThemeData(color: Colors.black, size: 33.0),
backgroundColor: Colors.white,
shadowColor: Colors.white,
elevation: 0,
actions: [
Container(
padding: const EdgeInsets.only(right: 19.0),
child: Badge(
badgeColor: Colors.amberAccent,
badgeContent: Text("${Panier.art.length}"),
animationType: BadgeAnimationType.fade,
child: IconButton(onPressed: () => Navigator.push(context, MaterialPageRoute(
builder: (context) => Panier(products: <Product> [
//Product(nom: widget.mail, mail: widget.mail)
],)
)
),
icon: const Icon(Icons.shopping_cart_outlined))),
)
],
bottom: PreferredSize(
child: Container(
alignment: Alignment.bottomLeft,
margin: const EdgeInsets.only(left: 50.0),
child: const Text("Produits en promo",
style: TextStyle(
fontSize: 19.0,
fontWeight: FontWeight.w500,
color: Colors.blue
),
),
),
preferredSize: const Size.fromHeight(20.0),
),
),
body: SingleChildScrollView(
child: Column(
children: [
const SizedBox(height: 20.0,),
GridView.builder(
shrinkWrap: true,
physics: const NeverScrollableScrollPhysics(),
gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
itemCount: userdata == null ? 0 : _count,
itemBuilder: (context, index) {
debugPrint(userdata[index]['photo'].toString());
return userdata == null ? const Center(child: Text('Aucune donnees !'),)
: GestureDetector(
onTap: () => Navigator.push(context, MaterialPageRoute(
builder: (_) => DetailArticle(
id: userdata[index]['id'],
titre: userdata[index]['title'],
description: userdata[index]['description'],
prix: userdata[index]['realPrice'],
image: userdata[index]['pictures'],
prixPromo: userdata[index]["discountPrice"],
//.toString() == null ?
//"https://www.kaomini.ne/uploads/images/logo.png" :
//userdata[index]['photo'],
)
)
),
child: Card(
margin: const EdgeInsets.all(10.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
//Image.network(userdata[index]['photo'].toString()),
Expanded(
flex: 2,
child: userdata[index]["pictures"] == null ? MyAssetImage.logo1 :
Image.network("https://kaomini.ne/uploads/productPictures/"+userdata[index]["pictures"]),//MyAssetImage.img2
),
Expanded(
child: ListTile(
enabled: false,
title: Row(
children: [
Expanded(
flex: 2,
child: Text(userdata[index]["discountPrice"]+' FCFA',
style: const TextStyle(
color: Colors.blue,
fontWeight: FontWeight.w500,
fontSize: 17.0
),
textAlign: TextAlign.center,
),
),
Expanded(
child: Text(userdata[index]["realPrice"],
style: const TextStyle(
color: Colors.grey,
decoration: TextDecoration.lineThrough,
fontWeight: FontWeight.w300,
fontSize: 15.0
),
textAlign: TextAlign.center,
),
),
],
),
subtitle: Text(userdata[index]["title"],
style: const TextStyle(
fontWeight: FontWeight.w300,
fontSize: 15.0
),
textAlign: TextAlign.center,
),
),
),
],
),
),
);
},
),
ElevatedButton(onPressed: increment,
style: ElevatedButton.styleFrom(
minimumSize: const Size(400, 50),
primary: Colors.blue[100],
shape: const RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(20.0)),)
),
child: const Text("Voir plus", style: TextStyle(color: Colors.white, fontSize: 16),)
),
],
),
),
endDrawer: const MyMenu(),
);
}
} ```

Answer 1

Change
itemCount: userdata == null ? 0 : _count,
to
itemCount: userdata.isEmpty ? 0 : _count,
or
itemCount: userdata.length,