Reset DropDownMenu - flutter

Question

I have a page with a DropdownButton.
The hint is 'Select your choice'.
When an item is selected in the DropdownButton when I click on a button I want the DropdownButton to go back to the beginning and show 'Select your choice' again.
child: DropdownButton<String> (
hint: Text(
'Select your choice',
style: TextStyle(
color: Colors.white,
fontFamily: 'Quicksand',
),
),
borderRadius: BorderRadius.circular(10),
dropdownColor: Color.fromRGBO(84, 84, 84, 10),
icon: const Icon(
Icons.arrow_drop_down,
color: Colors.white,
),
iconSize: 40,
isExpanded: true,
underline: SizedBox(),
style: TextStyle(
fontSize: 20,
color: Colors.white,
fontFamily: 'Quicksand',
),
items: [
DropdownMenuItem(
child: Text(listaMedidas[0]),
value: listaMedidas[0],
),
DropdownMenuItem(
child: Text(listaMedidas[1]),
value: listaMedidas[1],
),
DropdownMenuItem(
child: Text(listaMedidas[2]),
value: listaMedidas[2],
),
DropdownMenuItem(
child: Text(listaMedidas[3]),
value: listaMedidas[3],
),
],
onChanged: (value) => setState(() {
escolha = value;
limpar();
textoObservacao(value);
}),
value: escolha,
),

Answer 1

You can set null value to the DropdownButton, it will show the hint text.
class DropDownButtonTest extends StatefulWidget {
const DropDownButtonTest({Key? key}) : super(key: key);
#override
State<DropDownButtonTest> createState() => _DropDownButtonTestState();
}
class _DropDownButtonTestState extends State<DropDownButtonTest> {
List<String> listaMedidas = ["A", "B"];
String? escolha;
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
children: [
DropdownButton<String>(
hint: Text(
'Select your choice',
style: TextStyle(
color: Colors.white,
fontFamily: 'Quicksand',
),
),
borderRadius: BorderRadius.circular(10),
dropdownColor: Color.fromRGBO(84, 84, 84, 10),
icon: const Icon(
Icons.arrow_drop_down,
color: Colors.white,
),
iconSize: 40,
isExpanded: true,
underline: SizedBox(),
style: TextStyle(
fontSize: 20,
color: Colors.white,
fontFamily: 'Quicksand',
),
items: [
for (int i = 0; i < listaMedidas.length; i++)
DropdownMenuItem(
child: Text(listaMedidas[i]),
value: listaMedidas[i],
),
],
onChanged: (value) => setState(() { escolha = value;}),
value: escolha,
),
ElevatedButton(
onPressed: () {
setState(() {
escolha = null;
});
},
child: Text("Reset"),
),
],
),
);
}
}