How to populating 2nd DropdownMenu based on first item selected flutter
I'm populating states name from JSON and display as a dropdown list after that I show 2nd dropdown list based on first value selected. But I don't now how to populate 2nd dropdown when 1st dropdown value changed. I also want to get location id, name and city when select 2nd dropdown value.
My Json
{
"data": [
{
"state": "TEXAS",
"locations": [
{
"id": 1,
"name": "FITT Sugarland",
"city": "HOUSTON",
"state": "TEXAS",
"timezone": "",
"ownerName": "",
"ownerPhoneNumber": "",
"ownerEmail": "",
"ownerWebsite": "",
"capacity": 0,
"description": "HOUSTON SUGARLAND",
"createdBy": "",
"modifiedBy": "",
"createdAt": "2020-08-18T10:17:55.000Z",
"modifiedAt": "2020-08-18T10:17:55.000Z"
},
{
"id": 2,
"name": "FITT Pearland",
"city": "HOUSTON",
"state": "TEXAS",
"timezone": "",
"ownerName": "",
"ownerPhoneNumber": "",
"ownerEmail": "",
"ownerWebsite": "",
"capacity": 0,
"description": "second location",
"createdBy": "",
"modifiedBy": "",
"createdAt": "2020-08-18T10:18:38.000Z",
"modifiedAt": "2020-08-18T10:18:38.000Z"
}
]
}
]
}
Model Class
class LocationModel {
List<LocationList> data;
LocationModel({this.data});
LocationModel.fromJson(Map<String, dynamic> json) {
if (json['data'] != null) {
data = new List<LocationList>();
json['data'].forEach((v) {
data.add(new LocationList.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
if (this.data != null) {
data['data'] = this.data.map((v) => v.toJson()).toList();
}
return data;
}
}
class LocationList {
String state;
List<Locations> locations;
LocationList({this.state, this.locations});
LocationList.fromJson(Map<String, dynamic> json) {
state = json['state'];
if (json['locations'] != null) {
locations = new List<Locations>();
json['locations'].forEach((v) {
locations.add(new Locations.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['state'] = this.state;
if (this.locations != null) {
data['locations'] = this.locations.map((v) => v.toJson()).toList();
}
return data;
}
}
class Locations {
int id;
String name;
String city;
String state;
String timezone;
String ownerName;
String ownerPhoneNumber;
String ownerEmail;
String ownerWebsite;
int capacity;
String description;
String createdBy;
String modifiedBy;
String createdAt;
String modifiedAt;
Locations(
{this.id,
this.name,
this.city,
this.state,
this.timezone,
this.ownerName,
this.ownerPhoneNumber,
this.ownerEmail,
this.ownerWebsite,
this.capacity,
this.description,
this.createdBy,
this.modifiedBy,
this.createdAt,
this.modifiedAt});
Locations.fromJson(Map<String, dynamic> json) {
id = json['id'];
name = json['name'];
city = json['city'];
state = json['state'];
timezone = json['timezone'];
ownerName = json['ownerName'];
ownerPhoneNumber = json['ownerPhoneNumber'];
ownerEmail = json['ownerEmail'];
ownerWebsite = json['ownerWebsite'];
capacity = json['capacity'];
description = json['description'];
createdBy = json['createdBy'];
modifiedBy = json['modifiedBy'];
createdAt = json['createdAt'];
modifiedAt = json['modifiedAt'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = new Map<String, dynamic>();
data['id'] = this.id;
data['name'] = this.name;
data['city'] = this.city;
data['state'] = this.state;
data['timezone'] = this.timezone;
data['ownerName'] = this.ownerName;
data['ownerPhoneNumber'] = this.ownerPhoneNumber;
data['ownerEmail'] = this.ownerEmail;
data['ownerWebsite'] = this.ownerWebsite;
data['capacity'] = this.capacity;
data['description'] = this.description;
data['createdBy'] = this.createdBy;
data['modifiedBy'] = this.modifiedBy;
data['createdAt'] = this.createdAt;
data['modifiedAt'] = this.modifiedAt;
return data;
}
}
My Code
import 'dart:io';
import 'package:fittheorem/models/location_list.dart';
import 'package:fittheorem/providers/auth_session.dart';
import 'package:fittheorem/providers/user_details.dart';
import 'package:fittheorem/ui/widgets/error_snakbar.dart';
import 'package:fittheorem/utils/app_config.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:provider/provider.dart';
class LocationUpdate extends StatefulWidget {
@override
_LocationUpdateState createState() => _LocationUpdateState();
}
class _LocationUpdateState extends State<LocationUpdate> {
LocationModel _locationModel;
bool isLoading = true;
String _selectedState = "TEXAS";
List<String> _statesList = [];
String _selectedLocation = "FITT Sugarland";
List<Locations> _locationsList = List();
@override
void initState() {
// TODO: implement initState
super.initState();
getList();
}
Future<void> getList() async {
try {
_locationModel = await Provider.of<UserDetails>(context, listen: false)
.getLocationList("token");
for (int i = 0; i < _locationModel.data.length; i++) {
_statesList.add(_locationModel.data[i].state);
}
_locationsList = _locationModel.data[0].locations;
_selectedState = _statesList[0];
_selectedLocation = _locationsList[0].name;
if (mounted) {
setState(() {
isLoading = false;
});
}
} on HttpException catch (error) {
CustomWidgets.buildErrorSnackbar(context);
} catch (error) {
CustomWidgets.buildErrorSnackbar(context);
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
color: AppConfig.bgColor,
child: SafeArea(
child: Column(
children: <Widget>[
Container(
padding: EdgeInsets.fromLTRB(20.0, 10.0, 20.0, 10.0),
height: 40.0,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
GestureDetector(
behavior: HitTestBehavior.translucent,
onTap: () {
Navigator.pop(context, true);
},
child: Container(
height: 25.0,
width: 25.0,
child: SvgPicture.asset(AppConfig.backImage,
color: Colors.white, semanticsLabel: 'back')),
),
Text('LOCATION',
style: GoogleFonts.roboto(
textStyle: TextStyle(
fontSize: 18.0, color: Color(0xffFFFFFF)),
)),
SizedBox(
width: 25.0,
),
],
),
),
Expanded(
child: Container(
color: Colors.white,
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
padding: EdgeInsets.all(30.0),
child: isLoading
? Center(
child: AppConfig().myLoader(),
)
: Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
SizedBox(
height: 20.0,
),
Padding(
padding: const EdgeInsets.only(left: 5.0),
child: Text('UPDATE YOUR LOCATION',
style: GoogleFonts.roboto(
textStyle: TextStyle(
fontSize: 16.0,
color: Color(0xff000000)),
)),
),
SizedBox(
height: 20.0,
),
Container(
height: 40.0,
decoration: new BoxDecoration(
border: new Border.all(
color: Colors.black54, width: 0.0),
borderRadius: new BorderRadius.circular(10.0),
),
child: new DropdownButtonHideUnderline(
child: ButtonTheme(
alignedDropdown: true,
child: new DropdownButton(
value: _selectedState,
hint: Text("State"),
isExpanded: true,
items: _statesList
.map((String item) =>
DropdownMenuItem<String>(
child: Text(item),
value: item))
.toList(),
onChanged: (String newValue) {
if (mounted)
setState(() {
_selectedState = newValue;
});
},
style: Theme.of(context)
.textTheme
.bodyText2,
))),
),
SizedBox(
height: 20.0,
),
Container(
height: 40.0,
decoration: new BoxDecoration(
border: new Border.all(
color: Colors.black54, width: 0.0),
borderRadius: new BorderRadius.circular(10.0),
),
child: new DropdownButtonHideUnderline(
child: ButtonTheme(
alignedDropdown: true,
child: new DropdownButton(
value: _selectedLocation,
hint: Text("Location"),
isExpanded: true,
items: _locationsList.map((item) {
return new DropdownMenuItem(
child: new Text(item.name),
value: item.name,
);
}).toList(),
onChanged: (newValue) {
if (mounted) print(newValue);
setState(() {
_selectedLocation = newValue;
});
},
style: Theme.of(context)
.textTheme
.bodyText2,
))),
)
],
),
),
)
],
),
),
),
);
}
}
asked on Stack Overflow Aug 19, 2020 by 
Gursewak Singh
Gursewak Singh1 Answer
You can copy paste run full code below
Step 1: Change data type of _selectedLocation
Locations _selectedLocation;
Step 2: _selectedState's onChanged
onChanged: (String Value) {
if (mounted)
setState(() {
_selectedState = Value;
int index = _locationModel.data
.indexWhere((element) =>
element.state ==
_selectedState);
_locationsList = _locationModel
.data[index].locations;
_selectedLocation =
_locationsList[0];
});
},
Step 3: _selectedLocation's onChanged
onChanged: (Value) {
if (mounted) print(Value);
setState(() {
_selectedLocation = Value;
print(
"${_selectedLocation.name} ${_selectedLocation.id} ${_selectedLocation.city}");
});
},
working demo
full code
import 'dart:convert';
import 'package:flutter/material.dart';
LocationModel locationModelFromJson(String str) =>
LocationModel.fromJson(json.decode(str));
class LocationModel {
List<LocationList> data;
LocationModel({this.data});
LocationModel.fromJson(Map<String, dynamic> json) {
if (json['data'] != null) {
data = List<LocationList>();
json['data'].forEach((v) {
data.add(LocationList.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = Map<String, dynamic>();
if (this.data != null) {
data['data'] = this.data.map((v) => v.toJson()).toList();
}
return data;
}
}
class LocationList {
String state;
List<Locations> locations;
LocationList({this.state, this.locations});
LocationList.fromJson(Map<String, dynamic> json) {
state = json['state'];
if (json['locations'] != null) {
locations = List<Locations>();
json['locations'].forEach((v) {
locations.add(Locations.fromJson(v));
});
}
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = Map<String, dynamic>();
data['state'] = this.state;
if (this.locations != null) {
data['locations'] = this.locations.map((v) => v.toJson()).toList();
}
return data;
}
}
class Locations {
int id;
String name;
String city;
String state;
String timezone;
String ownerName;
String ownerPhoneNumber;
String ownerEmail;
String ownerWebsite;
int capacity;
String description;
String createdBy;
String modifiedBy;
String createdAt;
String modifiedAt;
Locations(
{this.id,
this.name,
this.city,
this.state,
this.timezone,
this.ownerName,
this.ownerPhoneNumber,
this.ownerEmail,
this.ownerWebsite,
this.capacity,
this.description,
this.createdBy,
this.modifiedBy,
this.createdAt,
this.modifiedAt});
Locations.fromJson(Map<String, dynamic> json) {
id = json['id'];
name = json['name'];
city = json['city'];
state = json['state'];
timezone = json['timezone'];
ownerName = json['ownerName'];
ownerPhoneNumber = json['ownerPhoneNumber'];
ownerEmail = json['ownerEmail'];
ownerWebsite = json['ownerWebsite'];
capacity = json['capacity'];
description = json['description'];
createdBy = json['createdBy'];
modifiedBy = json['modifiedBy'];
createdAt = json['createdAt'];
modifiedAt = json['modifiedAt'];
}
Map<String, dynamic> toJson() {
final Map<String, dynamic> data = Map<String, dynamic>();
data['id'] = this.id;
data['name'] = this.name;
data['city'] = this.city;
data['state'] = this.state;
data['timezone'] = this.timezone;
data['ownerName'] = this.ownerName;
data['ownerPhoneNumber'] = this.ownerPhoneNumber;
data['ownerEmail'] = this.ownerEmail;
data['ownerWebsite'] = this.ownerWebsite;
data['capacity'] = this.capacity;
data['description'] = this.description;
data['createdBy'] = this.createdBy;
data['modifiedBy'] = this.modifiedBy;
data['createdAt'] = this.createdAt;
data['modifiedAt'] = this.modifiedAt;
return data;
}
}
class LocationUpdate extends StatefulWidget {
@override
_LocationUpdateState createState() => _LocationUpdateState();
}
class _LocationUpdateState extends State<LocationUpdate> {
LocationModel _locationModel;
bool isLoading = true;
String _selectedState = "TEXAS";
List<String> _statesList = [];
Locations _selectedLocation;
List<Locations> _locationsList = List();
@override
void initState() {
// TODO: implement initState
super.initState();
getList();
}
Future<void> getList() async {
try {
/*_locationModel = await Provider.of<UserDetails>(context, listen: false)
.getLocationList("token");*/
String jsonString = '''
{
"data": [
{
"state": "TEXAS",
"locations": [
{
"id": 1,
"name": "FITT Sugarland",
"city": "HOUSTON",
"state": "TEXAS",
"timezone": "",
"ownerName": "",
"ownerPhoneNumber": "",
"ownerEmail": "",
"ownerWebsite": "",
"capacity": 0,
"description": "HOUSTON SUGARLAND",
"createdBy": "",
"modifiedBy": "",
"createdAt": "2020-08-18T10:17:55.000Z",
"modifiedAt": "2020-08-18T10:17:55.000Z"
},
{
"id": 2,
"name": "FITT Pearland",
"city": "HOUSTON",
"state": "TEXAS",
"timezone": "",
"ownerName": "",
"ownerPhoneNumber": "",
"ownerEmail": "",
"ownerWebsite": "",
"capacity": 0,
"description": "second location",
"createdBy": "",
"modifiedBy": "",
"createdAt": "2020-08-18T10:18:38.000Z",
"modifiedAt": "2020-08-18T10:18:38.000Z"
}
]
},
{
"state": "A",
"locations": [
{
"id": 1,
"name": "A1",
"city": "A City 1",
"state": "A",
"timezone": "",
"ownerName": "",
"ownerPhoneNumber": "",
"ownerEmail": "",
"ownerWebsite": "",
"capacity": 0,
"description": "HOUSTON SUGARLAND",
"createdBy": "",
"modifiedBy": "",
"createdAt": "2020-08-18T10:17:55.000Z",
"modifiedAt": "2020-08-18T10:17:55.000Z"
},
{
"id": 2,
"name": "A2",
"city": "A city 2",
"state": "A",
"timezone": "",
"ownerName": "",
"ownerPhoneNumber": "",
"ownerEmail": "",
"ownerWebsite": "",
"capacity": 0,
"description": "second location",
"createdBy": "",
"modifiedBy": "",
"createdAt": "2020-08-18T10:18:38.000Z",
"modifiedAt": "2020-08-18T10:18:38.000Z"
}
]
}
]
}
''';
_locationModel = locationModelFromJson(jsonString);
for (int i = 0; i < _locationModel.data.length; i++) {
_statesList.add(_locationModel.data[i].state);
}
_locationsList = _locationModel.data[0].locations;
_selectedState = _statesList[0];
_selectedLocation = _locationsList[0];
if (mounted) {
setState(() {
isLoading = false;
});
}
//} on HttpException catch (error) {
// CustomWidgets.buildErrorSnackbar(context);
} catch (error) {
//CustomWidgets.buildErrorSnackbar(context);
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
//color: AppConfig.bgColor,
child: SafeArea(
child: Column(
children: <Widget>[
Container(
padding: EdgeInsets.fromLTRB(20.0, 10.0, 20.0, 10.0),
height: 40.0,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
GestureDetector(
behavior: HitTestBehavior.translucent,
onTap: () {
Navigator.pop(context, true);
},
child: Container(
height: 25.0,
width: 25.0,
child: Image.network(
'https://picsum.photos/250?image=9',
color: Colors.white)),
),
Text('LOCATION',
style: TextStyle(
fontSize: 18.0,
color: Color(0xffFFFFFF),
)),
SizedBox(
width: 25.0,
),
],
),
),
Expanded(
child: Container(
color: Colors.white,
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
padding: EdgeInsets.all(30.0),
child: isLoading
? Center(
child: CircularProgressIndicator(),
)
: Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
SizedBox(
height: 20.0,
),
Padding(
padding: const EdgeInsets.only(left: 5.0),
child: Text('UPDATE YOUR LOCATION',
style: TextStyle(
fontSize: 16.0,
color: Color(0xff000000),
)),
),
SizedBox(
height: 20.0,
),
Container(
height: 40.0,
decoration: BoxDecoration(
border: Border.all(
color: Colors.black54, width: 0.0),
borderRadius: BorderRadius.circular(10.0),
),
child: DropdownButtonHideUnderline(
child: ButtonTheme(
alignedDropdown: true,
child: DropdownButton(
value: _selectedState,
hint: Text("State"),
isExpanded: true,
items: _statesList
.map((String item) =>
DropdownMenuItem<String>(
child: Text(item),
value: item))
.toList(),
onChanged: (String Value) {
if (mounted)
setState(() {
_selectedState = Value;
int index = _locationModel.data
.indexWhere((element) =>
element.state ==
_selectedState);
_locationsList = _locationModel
.data[index].locations;
_selectedLocation =
_locationsList[0];
});
},
style: Theme.of(context)
.textTheme
.bodyText2,
))),
),
SizedBox(
height: 20.0,
),
Container(
height: 40.0,
decoration: BoxDecoration(
border: Border.all(
color: Colors.black54, width: 0.0),
borderRadius: BorderRadius.circular(10.0),
),
child: DropdownButtonHideUnderline(
child: ButtonTheme(
alignedDropdown: true,
child: DropdownButton(
value: _selectedLocation,
hint: Text("Location"),
isExpanded: true,
items: _locationsList.map((item) {
return DropdownMenuItem(
child: Text(item.name),
value: item,
);
}).toList(),
onChanged: (Value) {
if (mounted) print(Value);
setState(() {
_selectedLocation = Value;
print(
"${_selectedLocation.name} ${_selectedLocation.id} ${_selectedLocation.city}");
});
},
style: Theme.of(context)
.textTheme
.bodyText2,
))),
)
],
),
),
)
],
),
),
),
);
}
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: LocationUpdate(),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
answered on Stack Overflow Aug 19, 2020 by 
chunhunghan
chunhunghanUser contributions licensed under CC BY-SA 3.0