I am trying to get some String data from a server via future builder, which works. Then transfer those strings into the dropdownbutton thing, to show as options then to be picked. I mean they will show up on dropdownbutton. Think of it like, I will choose a person to do a job here, I get the names from a database and show it on screen. So user can choose from there. Here is the important data that supposedly gets the dropdown data from the futurebuilder:
String dropdownValue = _MyAppState.data2.first;
It gives the following error:
Bad state: No element
And here is my code:
import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
const List<String> list = <String>['One', 'Two', 'Three', 'Four'];
Future<List<Album>> fetchAlbum() async {
final response = await http.get(
Uri.parse('https://my-json-server.typicode.com/fluttirci/testJson/db'));
//this was for testing.
//print(response);
Map<String, dynamic> userMap = jsonDecode(response.body);
if (response.statusCode == 200) {
return (userMap['employees'] as List)
.map((e) => Album.fromJson(e))
.toList();
} else {
throw Exception('Failed to load album');
}
}
class Album {
final int userId;
final int id;
final String title;
Album(this.userId, this.id, this.title);
Album.fromJson(Map<String, dynamic> json)
: userId = json['userId'],
id = json['id'],
title = json['title'];
Map<String, dynamic> toJson() => {
'userId': userId,
'id': id,
'title': title,
};
}
void main() => runApp(const MyApp());
class MyApp extends StatefulWidget {
const MyApp({super.key});
@override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
late Future<Album> futureAlbum;
late Future<List<Album>> user;
late List<Album> data;
static List<String> data2 = [];
@override
void initState() {
super.initState();
user = fetchAlbum();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Fetch Data Example',
theme: ThemeData(
brightness: Brightness.dark,
primarySwatch: Colors.blue,
),
home: Scaffold(
appBar: AppBar(
title: const Text('Fetch Data Example'),
),
body: Column(children: <Widget>[
const Expanded(
child: DropdownButtonExample(),
),
Expanded(
child: FutureBuilder<List<Album>>(
future: user,
builder: (context, snapshot) {
if (snapshot.hasData) {
data = snapshot.data ?? [];
return ListView.builder(
itemBuilder: (context, index) {
data2.add(data[index].title);
print('data2 was fetched: ${data2[index]}');
return Column(
children: [
Text(data[index].title),
],
);
},
itemCount: data.length,
);
} else if (snapshot.hasError) {
return Text(
'${snapshot.error}',
);
}
return const Center(
child: CircularProgressIndicator(),
);
},
),
)
]),
),
);
}
}
class DropdownButtonApp extends StatelessWidget {
const DropdownButtonApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: const Text('DropdownButton Sample')),
body: const Center(
child: DropdownButtonExample(),
),
),
);
}
}
class DropdownButtonExample extends StatefulWidget {
const DropdownButtonExample({super.key});
@override
State<DropdownButtonExample> createState() => _DropdownButtonExampleState();
}
class _DropdownButtonExampleState extends State<DropdownButtonExample> {
String dropdownValue = _MyAppState.data2.first;
@override
Widget build(BuildContext context) {
return DropdownButton<String>(
value: dropdownValue,
icon: const Icon(Icons.arrow_downward),
elevation: 16,
style: const TextStyle(color: Colors.deepPurple),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (String? value) {
// This is called when the user selects an item.
setState(() {
dropdownValue = value!;
});
},
items: list.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
);
}
}
There are more than one error in your code.
Error 1 :
You are trying to access first element from empty list. At
String dropdownValue = _MyAppState.data2.first;
Actual issue of Bad state: No element
You can give only dropdown items as value. In your case the data coming from api and hardcoded list List<String> list = <String>['One', 'Two', 'Three', 'Four'];
both are different.
Hope this helps