For Example This is the First Dropdownbutton For Example This is the First Dropdown Sorry i dont have enough Reputation to post the images
Where the Tag will be Select A Region and Another one will be showing which will be the cities where the cities will be listed down there depends on the region selected above somewhat like that.
Each time you call setState the build method of your widget will be called and the visual tree gets reconstructed where needed. So, in the onChanged handler for your DropdownButton, save the selection in setState and conditionally add the second DropdownButton. Here's a working example (which may be a little rough around the edges :) ):
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
String _selectedRegion;
String _selectedSecond;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text('Something before'),
DropdownButton<String>(
value: _selectedRegion,
items: ['Arizona', 'California']
.map((region) => DropdownMenuItem<String>(
child: Text(region), value: region))
.toList(),
onChanged: (newValue) {
setState(() {
_selectedRegion = newValue;
});
},
),
_addSecondDropdown(),
Text('Something after'),
],
),
),
);
}
Widget _addSecondDropdown() {
return _selectedRegion != null
? DropdownButton<String>(
value: _selectedSecond,
items: ['First', 'Second']
.map((region) => DropdownMenuItem<String>(
child: Text(region), value: region))
.toList(),
onChanged: (newValue) {
setState(() {
_selectedSecond = newValue;
});
})
: Container(); // Return an empty Container instead.
}
}
Luke Freeman has a great blog post about Managing visibility in Flutter if you need this in a more extensive/reusable way.
