How do I clear a Flutter DropdownButton programmatically? - flutter

Question

I have two dropdown buttons that are mutually exclusive. How can I clear (or set) the value of one when the other is set?
Thanks

Answer 1

for 1st dropdown:
onChanged: (String newValue) {
setState(() {
dropdownValueFirst = newValue;
dropdownValueSecond = "Bangladesh";
});
},
for 2nd dropdown:
onChanged: (String newValue) {
setState(() {
dropdownValueSecond = newValue;
dropdownValueFirst ="One";
});
},
See below code:
import 'package:flutter/material.dart';
import 'package:font_awesome_flutter/font_awesome_flutter.dart';
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,
),
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;
String dropdownValueFirst="One";
String dropdownValueSecond="Bangladesh";
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
DropdownButton<String>(
value: dropdownValueFirst,
icon: Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: TextStyle(
color: Colors.deepPurple
),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (String newValue) {
setState(() {
dropdownValueFirst = newValue;
dropdownValueSecond = "Bangladesh";
});
},
items: <String>['One', 'Two', 'Free', 'Four']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
})
.toList(),
),
const Padding(padding: EdgeInsets.only(left: 8)),
DropdownButton<String>(
value: dropdownValueSecond,
icon: Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: TextStyle(
color: Colors.deepPurple
),
underline: Container(
height: 2,
color: Colors.deepPurpleAccent,
),
onChanged: (String newValue) {
setState(() {
dropdownValueSecond = newValue;
dropdownValueFirst ="One";
});
},
items: <String>['Bangladesh', 'India', 'China']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
})
.toList(),
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}

Answer 2

When 1st drop down in pressed then try to reset value of 2nd dropdown inside setState on onChanged event and vice versa,
onChanged: (String newValue) {
setState(() {
dropdownValueFirst = newValue;
dropdownValueSecond='Initial Value of second',// remeber this value must be same as initial value of 2nd dropdown =>value: 'Initial Value of second',
});
},