Having issues with flutter dropdown items with same value - flutter

Question

Am new to flutter and am having issues giving same values to some of the dropdown items. Here is the code for the dropdown below
Expanded(
child: Padding(
padding: const EdgeInsets.only(
left: 20.0, right: 5.0, top: 5.0),
child: new Container(
alignment: Alignment.center,
height: 40.0,
decoration: new BoxDecoration(
color: Colors.cyan,
borderRadius: new BorderRadius.circular(30.0)),
child: DropdownButton<int>(
items: [
DropdownMenuItem<int>(
child: Text('S&P500'),
value: 10,
),
DropdownMenuItem<int>(
child: Text('WS30'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('TV-NDX'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('AUS200'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('JS225'),
value: 100,
),
DropdownMenuItem<int>(
child: Text('UK100'),
value: 1,
),DropdownMenuItem<int>(
child: Text('FCH1'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('STOXX50E'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('GDAX'),
value: 1,
),DropdownMenuItem<int>(
child: Text('BITCOIN'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('ETHEREUM'),
value: 1,
),
DropdownMenuItem<int>(
child: Text('NGS'),
value: 1000,
),
DropdownMenuItem<int>(
child: Text('CRUDEOIL'),
value: 100,
),
DropdownMenuItem<int>(
child: Text('UKOIL'),
value: 100,
),
DropdownMenuItem<int>(
child: Text('SPX-NDX'),
value: 10,
),
DropdownMenuItem<int>(
child: Text('SMI'),
value: 1,
),
],
onChanged: (int value) {
setState(() {
asset = value;
});
},
hint: Text("TRADEVIEW",
style: new TextStyle(
fontSize: 15.0, color: Colors.black),),
value: asset,
),
),
),
),

Answer 1

You can use a class to hold name and value. so you can identify duplicate value with name
For demo only, I did not list all you data
code snippet
class Data {
String name;
int value;
Data({
this.name,
this.value,
});
factory Data.fromJson(Map<String, dynamic> json) => Data(
name: json["name"] == null ? null : json["name"],
value: json["value"] == null ? null : json["value"],
);
Map<String, dynamic> toJson() => {
"name": name == null ? null : name,
"value": value == null ? null : value,
};
}
List<Data> dataList = [
Data(name: 'CRUDEOIL', value: 100),
Data(name: "UKOIL", value: 100)
];
DropdownButton<Data>(
items: dataList.map<DropdownMenuItem<Data>>((Data value) {
return DropdownMenuItem<Data>(
value: value,
child: Text(value.name),
);
}).toList(),
onChanged: (Data value) {
setState(() {
asset = value;
print('${asset.name} ${asset.value}');
});
}
full code
import 'package:flutter/material.dart';
// To parse this JSON data, do
//
// final data = dataFromJson(jsonString);
import 'dart:convert';
Data dataFromJson(String str) => Data.fromJson(json.decode(str));
String dataToJson(Data data) => json.encode(data.toJson());
class Data {
String name;
int value;
Data({
this.name,
this.value,
});
factory Data.fromJson(Map<String, dynamic> json) => Data(
name: json["name"] == null ? null : json["name"],
value: json["value"] == null ? null : json["value"],
);
Map<String, dynamic> toJson() => {
"name": name == null ? null : name,
"value": value == null ? null : value,
};
}
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(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
Data asset;
List<Data> dataList = [
Data(name: 'CRUDEOIL', value: 100),
Data(name: "UKOIL", value: 100)
];
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
#override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Expanded(
child: Padding(
padding:
const EdgeInsets.only(left: 20.0, right: 5.0, top: 5.0),
child: new Container(
alignment: Alignment.center,
height: 40.0,
decoration: new BoxDecoration(
color: Colors.cyan,
borderRadius: new BorderRadius.circular(30.0)),
child: DropdownButton<Data>(
items: dataList.map<DropdownMenuItem<Data>>((Data value) {
return DropdownMenuItem<Data>(
value: value,
child: Text(value.name),
);
}).toList(),
onChanged: (Data value) {
setState(() {
asset = value;
print('${asset.name} ${asset.value}');
});
},
hint: Text(
"TRADEVIEW",
style: new TextStyle(fontSize: 15.0, color: Colors.black),
),
value: asset,
),
),
),
)
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}