The argument type 'int?' can't be assigned to the parameter type 'int' - class

Question

this is RadioModel.dart
I am a beginner in flutter and I want to display my JSON file data on vx swipper.builder but i don't know whats going on here when i pass item count i face this error i know i am doing something wrong and i can't fix this
I am a beginner in flutter and I want to display my JSON file data on vx swipper.builder but i don't know whats going on here when i pass item count i face this error i know i am doing something wrong and i can't fix this
I am a beginner in flutter and I want to display my JSON file data on vx swipper.builder but i don't know whats going on here when i pass item count i face this error i know i am doing something wrong and i can't fix this
import 'dart:convert';
class MyRadioList {
static List<MyRadio>? radios;
// Get Item by ID
MyRadio getById(int id) =>
radios!.firstWhere((element) => element.id == id, orElse: null);
// Get Item by position
MyRadio getByPosition(int pos) => radios![pos];
}
class MyRadio {
final int id;
final int order;
final String name;
final String tagline;
final String color;
final String desc;
final String url;
final String category;
final String icon;
final String image;
final String lang;
MyRadio({
required this.id,
required this.order,
required this.name,
required this.tagline,
required this.color,
required this.desc,
required this.url,
required this.category,
required this.icon,
required this.image,
required this.lang,
});
factory MyRadio.fromMap(Map<String, dynamic> map) {
return MyRadio(
id: map['id'],
order: map['order'],
name: map['name'],
tagline: map['tagline'],
color: map['color'],
desc: map['desc'],
url: map['url'],
category: map['category'],
icon: map['icon'],
image: map['image'],
lang: map['lang'],
);
}
toMap() => {
"id": id,
"order": order,
"name": name,
"tagline": tagline,
"color": color,
"desc": desc,
"url": url,
"category": category,
"icon": icon,
"image": image,
"lang": lang,
};
}
// this is HomePage.dart
import 'dart:convert';
import 'dart:ffi';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_application_1/models/RadioModel.dart';
import 'package:flutter_application_1/utils/Ai_Utils.dart';
import 'package:velocity_x/velocity_x.dart';
class HomePage extends StatefulWidget {
const HomePage({Key? key}) : super(key: key);
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
//get daata from radio model
#override
void initstate() {
super.initState();
fetchradios();
}
fetchradios() async {
final radioJson = await rootBundle.loadString("assets/radio.json");
final decodedData = jsonDecode(radioJson);
MyRadioList.radios = List.from(decodedData)
.map<MyRadio>(((radio) => MyRadio.fromMap(radio)))
.toList();
setState(() {});
}
#override
Widget build(BuildContext context) {
return Scaffold(
drawer: Drawer(),
body: Stack(children: [
VxAnimatedBox()
.withGradient(LinearGradient(
colors: [AiColors.primaryColor1, AiColors.primaryColor2],
begin: Alignment.topLeft,
end: Alignment.bottomRight,
))
.size(context.screenWidth, context.screenHeight)
.make(),
AppBar(
title: "AI Radio".text.xl4.bold.white.make().shimmer(
primaryColor: Vx.purple300, secondaryColor: Colors.white),
elevation: 0.0,
backgroundColor: Colors.transparent,
centerTitle: true,
).h(100.0).p16(),
VxSwiper.builder(
itemCount: MyRadioList.radios?.length, // error line
itemBuilder: (context, index) {
final rad = MyRadioList.radios![index];
return VxBox(child: ZStack([]))
.bgImage(DecorationImage(image: NetworkImage(rad.image)))
.make();
})
]),
);
}
}

Answer 1

itemCount must be a non-nullable int.
But your static List<MyRadio>? radios is a nullable List, so the length may be null if the List is never initialized
You can use the If-null operator ?? to initialize it to 0 or whatever default value you want to use if the length happens to be null
Change this line:
itemCount: MyRadioList.radios?.length, // error line
To this:
itemCount: MyRadioList.radios?.length ?? 0 // 0 or whatever default value
The line above essentially reads if MyRadioList.radios?.length is not null, then use it, otherwise set MyRadioList.radios?.length to 0.
Using ?? ensures that the length of your list will never be null