How set form validation in widget flutter - flutter

Question

I'm working on flutter project .I have a revision form validator that is not working as expected. When I leave the TextFormField empty the validator doesn't show me anything. I want to stay on the revision form until I enter the values.
thanks in advance
my code :
class Revision extends StatefulWidget {
}
class _RevisionState extends State<Revision> with TickerProviderStateMixin {
final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
RevisionApi revisionApi = RevisionApi();
TextEditingController _Kilometrage_revisionController =
TextEditingController();
_showAddDialog() async {
await showDialog(
context: context,
builder: (context) => AlertDialog(
backgroundColor: Colors.white,
title: Text("Ajouter un évènement"),
content: StatefulBuilder(builder: (
BuildContext context,
StateSetter setState,
) {
return SingleChildScrollView(
child: Form(
key: _formKey,
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Row(children: [
Expanded(
child: DropdownButtonFormField(
decoration: InputDecoration(
hoverColor: Colors.white,
//contentPadding: EdgeInsets.only(left: 10, right: 15, top: 15),
labelText: 'Type',
alignLabelWithHint: true,
labelStyle: TextStyle(
color: kPrimaryColor,
),
enabledBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Colors.grey),
),
),
dropdownColor: Colors.white,
value: status,
items: <DropdownMenuItem>[
DropdownMenuItem(
// value: 'videnge',
value: 0,
child: InkWell(
child: Text('videnge'),
hoverColor: Colors.indigo,
),
),
DropdownMenuItem(
// value: 'visite technique',
value: 1,
child: Text('visite technique'),
),
DropdownMenuItem(
// value: 'assurance véhicule',
value: 2,
child: Text('assurance véhicule'),
),
DropdownMenuItem(
// value: 'autre',
value: 3,
child: Text('autre'),
),
],
onChanged: (value) {
setState(() {
status = value;
});
},
)),
]),
if (status == 1) visiTechniqueDropdown(),
]),
));
}),
actions: <Widget>[
TextButton(
child: Text(
"Enregistrer",
style: TextStyle(
color: Colors.red, fontWeight: FontWeight.bold),
),
onPressed: () {
if (status == null) return;
setState(() {
if (_events[_controller.selectedDay] != null) {
_events[_controller.selectedDay].add(status);
} else {
_events[_controller.selectedDay] = [status];
}
prefs.setString(
"events", json.encode(encodeMap(_events)));
status;
setRevision();
_KilometrageController.clear();
_eventController.clear();
_EmplacementController.clear();
_DateController.clear();
_repeat_revisionController.clear();
_revision_agenceController.clear();
_Kilometrage_revisionController.clear();
Navigator.of(context).pop();
// Navigator.pop(context);
});
},
),
new TextButton(
onPressed: () {
Navigator.of(context).pop();
},
child: const Text('Retour'),
),
],
));
}
void setRevision() async {
print("hello");
if (_formKey.currentState.validate()) {
String kilometrage_pour_vidange = _KilometrageController.text;
String revision_type = status.toString();
String revision_title = _eventController.text;
String revision_location = _EmplacementController.text;
String revision_date = _DateController.text;
String repeat_revision = _repeat_revisionController.text;
String revision_agence = _revision_agenceController.text;
String kilometrage_revision = _Kilometrage_revisionController.text;
revisionApi
.setRevision(
revision_type,
revision_title,
revision_date,
revision_location,
kilometrage_pour_vidange,
repeat_revision,
revision_agence,
kilometrage_revision,
)
.then((data) {
if (data != null) {
Navigator.pop(context);
Navigator.of(context).pop();
Navigator.push(
context, MaterialPageRoute(builder: (context) => Revision()));
}
ScaffoldMessenger.of(context)
.showSnackBar(SnackBar(content: Text(data)));
}).catchError((error) {
ScaffoldMessenger.of(context)
.showSnackBar(SnackBar(content: Text(error.toString())));
});
setState(() {});
}
}
Widget visiTechniqueDropdown() {
return Column(mainAxisSize: MainAxisSize.min, children: [
Row(
children: [
Flexible(
child: TextFormField(
onFieldSubmitted: (_) => FocusScope.of(context).nextFocus(),
validator: (value) {
if (value.isEmpty) {
return 'Password is required';
}
return null;
},
controller: _DateController,
cursorColor: kPrimaryColor,
decoration: InputDecoration(
labelText: 'Date',
alignLabelWithHint: true,
labelStyle: TextStyle(
color: kPrimaryColor,
),
enabledBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Colors.grey),
How i can set the validator correctly ?

Answer 1

This is for you. Thanks and enjoy
// Create a corresponding State class.
// This class holds data related to the form.
class MyFormState extends State<MyForm> {
// Create a global key that uniquely identifies the Form widget
// and allows validation of the form.
//
// Note: This is a GlobalKey<FormState>,
// not a GlobalKey<MyFormState>.
final _formKey = GlobalKey<FormState>();
#override
Widget build(BuildContext context) {
// Build a Form widget using the _formKey created above.
return Form(
key: _formKey,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
TextFormField(
// The validator receives the text that the user has entered.
validator: (value) {
if (value == null || value.isEmpty) {
return 'Please enter some text';
}
return null;
},
),
Padding(
padding: const EdgeInsets.symmetric(vertical: 16.0),
child: ElevatedButton(
onPressed: () {
// Validate returns true if the form is valid, or false otherwise.
if (_formKey.currentState!.validate()) {
// If the form is valid, display a snackbar. In the real world,
// you'd often call a server or save the information in a database.
// sendData();
ScaffoldMessenger.of(context)
.showSnackBar(SnackBar(content: Text('Processing Data')));
}
},
child: Text('Submit'),
),
),
],
),
);
}
}