Flutter - InputDatePickerFormField - flutter

Question

I'm trying to add a text field that will get the date in the input field. I'm using InputDatePickerFormField widget. The issue I'm finding that it does not show error when the date is incorrect.
Here is my code:
class _BirthDay extends StatefulWidget {
#override
__BirthDayState createState() => __BirthDayState();
}
class __BirthDayState extends State<_BirthDay> {
DateTime? selectedDate;
#override
Widget build(BuildContext context) {
final firstDate = DateTime(DateTime.now().year - 120);
final lastDate = DateTime.now();
return InputDatePickerFormField(
firstDate: firstDate,
lastDate: lastDate,
fieldLabelText: '${AppLocalizations.of(context)!.dateOfBirth}',
errorFormatText: '${AppLocalizations.of(context)!.dateOfBirthInvalid}',
errorInvalidText: '${AppLocalizations.of(context)!.dateOfBirthInvalid}',
onDateSubmitted: (date) {
print(date);
setState(() {
selectedDate = date;
});
},
onDateSaved: (date) {
print(date);
setState(() {
selectedDate = date;
});
},
);
}
}

Answer 1

One way that you can add a checker on your Text fields is by setting the fields as children of a Form. Using this, you'll be able to validate the values on your fields once submitted.
final _formKey = GlobalKey<FormState>();
...
Form(
key: _formKey,
child: InputDatePickerFormField(...),
)
Then you can run a check using _formKey.currentState!.validate()). Trigger this validation on any onClick or onPressed event.

Answer 2

You need to save the form to see the validations errors
_formKey2.currentState.save();
You can call it on the submit button