date can't see on the screen with setstate - flutter

Question

IconButton(
onPressed: () async {
DateTime? x = await showDatePicker(
context: context,
initialDate: DateTime.now(),
firstDate: DateTime.now(),
lastDate: DateTime(2040));
if (x == null) return;
setState(() {
final DateFormat formatter = DateFormat('yyyy-MM-dd');
String formattedDate = formatter.format(x);
print(formattedDate);
print(formattedDate.runtimeType);
});
},
icon: const Icon(UniconsLine.clock)),
Text(formattedDate ?? "EMPTY"),
I am seeing always empty my formattedDate variable below on the build method why doesnt work this code

Answer 1

Could you try to lift up the formattedDate? I think the Problem is that your variable is out of scope.
class DatePicker extends StatefulWidget {
const DatePicker({Key? key}) : super(key: key);
#override
State<DatePicker> createState() => _DatePickerState();
}
class _DatePickerState extends State<DatePicker> {
String? formattedDate;
#override
Widget build(BuildContext context) {
return Column(children: [
IconButton(
onPressed: () async {
DateTime? x = await showDatePicker(
context: context,
initialDate: DateTime.now(),
firstDate: DateTime.now(),
lastDate: DateTime(2040));
if (x == null) return;
setState(() {
final DateFormat formatter = DateFormat('yyyy-MM-dd');
formattedDate = formatter.format(x);
print(formattedDate);
print(formattedDate.runtimeType);
});
},
icon: const Icon(Icons.date_range)),
Text(formattedDate ?? "EMPTY"),
]);
}
}

Answer 2

The problem is in the scope of your variable formattedDate. It only exists inside setState because it was declared there.
Declare it at the beginning of the class.

Answer 3

You have redefined formattedDate inside setState() as a local variable. The field formattedDate you are using in Text(formattedDate ?? "EMPTY") is a totally different variable. It remains null, as you are not changing it at all. Just remove the String before formattedDate and it should be fine.
final DateFormat formatter = DateFormat('yyyy-MM-dd');
formattedDate = formatter.format(x); <-- This is your problem
print(formattedDate);