I have problems with DropdownButton in flutter - flutter

Question

Good morning friends, I am trying to use DropdownButton, it brings me the information but it shows me an error before I bring the information.
I printed the data to verify that it did not come empty and it is effectively bringing the list without any problem
This is the error shown:
enter image description here
This is the code that I am using
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
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,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key}) : super(key: key);
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String _mySelection;
final String url = "http://webmyls.com/php/getdata.php";
List data;
Future<String> getSWData() async {
var res = await http
.get(Uri.encodeFull(url), headers: {"Accept": "application/json"});
var resBody = json.decode(res.body);
setState(() {
data = resBody;
});
print(data);
return "Sucess";
}
#override
void initState() {
super.initState();
this.getSWData();
}
#override
Widget build(BuildContext context) {
return new Scaffold(
body: new Center(
child: new DropdownButton(
//data != null,
isDense: true,
hint: new Text("Select"),
items: data.map((item) {
return new DropdownMenuItem(
child: new Text(item['item_name']),
value: item['id'].toString(),
);
}).toList(),
onChanged: (newVal) {
setState(() {
_mySelection = newVal;
});
},
value: _mySelection,
),
),
);
}
}

Answer 1

Yeimer Initialize data : List data = List(); your issue will be resolved.

Answer 2

Create this widget:
Widget _myDropDown() {
if (data == null) return Center();
return new DropdownButton(
//data != null,
isDense: true,
hint: new Text("Select"),
items: data.map((item) {
return new DropdownMenuItem(
child: new Text(item['item_name']),
value: item['id'].toString(),
);
}).toList(),
onChanged: (newVal) {
setState(() {
_mySelection = newVal;
});
},
value: _mySelection,
);
}
and then put _myDropDown inside your Center