How to clear error message in TextFormField in Flutter - flutter

Question

In my code I validate phone number. If phone number is incorrect - I show error message. But, when user starts to edit number I want to hide this error message.
I've found the solution with currentState.reset(), but it seems not the good one. I have to handle issues with saving text and cursor position. And I still have one small artifact. Normally when I press and hold backspace - it deletes symbols one by one. If I do it when error message is shown - then error message disappears and only one symbol is deleted.
Does anybody know the right solution for this case?
final TextEditingController controller = TextEditingController();
final RegExp _phoneRegex = RegExp(r"^\+{1}\d{10, 15}\$");
bool isError = false;
TextSelection currentPosition;
return Column(
children: <Widget>[
Form(
key: _textKey,
child: TextFormField(
controller: controller,
validator: (str) {
isError = true;
if (str.isEmpty) {
return err_empty_field;
} else if (!_phoneRegex.hasMatch(str)) {
return err_invalid_phone;
}
isError = false;
},
),
onChanged: () {
if (controller.selection.start < 0 &&
controller.text.length > 0) {
TextSelection position =
controller.text.length > currentPosition.start
? currentPosition
: TextSelection.fromPosition(
TextPosition(offset: controller.text.length));
controller.selection = position;
}
if (isError) {
isError = false;
currentPosition = controller.selection;
if (currentPosition.start > controller.text.length) {
currentPosition = TextSelection.fromPosition(
TextPosition(offset: controller.text.length));
}
String currentText = controller.text;
_textKey.currentState.reset();
controller.text = currentText;
controller.selection = currentPosition;
}
},
),
RaisedButton(
onPressed: () {
_textKey.currentState.validate();
},
child: Text(login),
)
],
);

Answer 1

EDIT (Nov 2020)
autovalidate was deprecated after v1.19.0.
Instead use autovalidateMode:
Form(
autovalidateMode: AutovalidateMode.onUserInteraction`.
...
)
Original post
here is a suitable solution to this problem.
You don't actually need to use onChanged or any tips causing side-effects, I solved it by creating a class property which is initialized to false:
bool _autovalidate = false;
The Form Widget has a named property autovalidate. You should pass it the previous boolean:
Form(
key: _textKey,
autovalidate: _autovalidate,
...
)
And in your Submit button onPressed() method, you should update the _autovalidate boolean to be true if the form is invalid, this will make the form to auto validate the TextFormField on every onChanged call:
RaisedButton(
onPressed: () {
if (_textKey.currentState.validate()) {
print('valid');
} else {
print('invalid');
setState(() => _autoValidate = true);
}
},
child: Text(login),
)
I hope it helped Somebody.

Answer 2

January 2021
...
AutovalidateMode _autoValidate = AutovalidateMode.disabled;
Form(
key: _textKey,
autovalidateMode: _autovalidate,
...
)
RaisedButton(
onPressed: () {
if (_textKey.currentState.validate()) {
print('valid');
} else {
print('invalid');
setState(() => _autoValidate = AutovalidateMode.always);
}
},
child: Text("login"),
)

Answer 3

The problem here is errorText is automatically managed by the validator field of the TextFormField. At the same time, the simple solution is to handle the errorText manually.
Step 1: Create
String field, _errorText initialised to null. The field will hold the error message that needs to be shown.
Boolean field, _error initialised to false. The filed is true if there is an error otherwise false.
Step 2:
Assign _errorText to TextFormField
Step 3 (Important):
Make sure that TextFormField validator returns a null value.
Handle the validation here and assign the proper error message to _errorText.
Update _error state correspondingly.
Step 4 (Important):
Reset _errorText and _error. This will remove the error from field soon as you start editing.
Step 5:
Trigger field validation in the onFieldSubmitted and manage your code flow...
import 'package:flutter/material.dart';
class WorkGround extends StatefulWidget {
#override
_WorkGroundState createState() => _WorkGroundState();
}
class _WorkGroundState extends State<WorkGround> {
final _formKey = GlobalKey<FormState>();
final _usernameFocusNode = FocusNode();
final _phoneNumberFocusNode = FocusNode();
/*
* Step 1.
* */
String _userNameErrorText;
bool _userNameError = false;
String _phoneNumberErrorText;
bool _phoneNumberError = false;
#override
Widget build(BuildContext context) {
return Form(
key: _formKey,
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
TextFormField(
focusNode: _usernameFocusNode,
decoration: InputDecoration(
labelText: 'Username',
/*
* Step 2
* */
errorText: _userNameErrorText, // Handling error manually
),
textInputAction: TextInputAction.next,
/*
* Step 3
* */
validator: (value) {
setState(() {
if(value.isEmpty) {
_userNameError = true;
_userNameErrorText = 'Enter Username';
}
});
return null; // Return null to handle error manually.
},
/*
* Step 4
* */
onChanged: (value) {
setState(() {
_userNameError = false;
_userNameErrorText = null; // Resets the error
});
},
/*
* Step 5
* */
onFieldSubmitted: (value) {
_formKey.currentState.validate(); // Trigger validation
if(!_userNameError) {
FocusScope.of(context).requestFocus(_phoneNumberFocusNode);
}
},
),
TextFormField(
focusNode: _phoneNumberFocusNode,
decoration: InputDecoration(
labelText: 'Phone Number',
/*
* Step 2
* */
errorText: _phoneNumberErrorText, // Handling error manually
),
textInputAction: TextInputAction.done,
/*
* Step 3
* */
validator: (value) {
setState(() {
if(value.isEmpty) {
_phoneNumberError = true;
_phoneNumberErrorText = 'Enter Phone number';
} else if( value.length < 10) {
_phoneNumberError = true;
_phoneNumberErrorText = 'Invalid Phone number';
}
});
return null; // Return null to handle error manually.
},
/*
* Step 4
* */
onChanged: (value) {
setState(() {
_phoneNumberError = false;
_phoneNumberErrorText = null; // Resets the error
});
},
/*
* Step 5
* */
onFieldSubmitted: (value) {
_formKey.currentState.validate(); // Trigger validation
if(!_phoneNumberError) {
// submit form or whatever your code flow is...
}
},
),
],
),
),
);
}
}

Answer 4

I have achieved your both below functionality:
1) Hide error message when editing
2) validate input field when login button pressed
Note: i have commented phone number regex and put validation for
string length < 10 digit for testing.
import 'package:flutter/material.dart';
import 'package:flutter/foundation.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(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
void initState(){
super.initState();
}
final TextEditingController controller = TextEditingController();
// final RegExp _phoneRegex = RegExp(r"^\+{1}\d{10, 15}\$");
bool isError = false;
bool isWriting = false;
bool isLoginPressed = false;
int counter = 0;
String myErrorString = "";
TextSelection currentPosition;
final _textKey = GlobalKey<FormState>();
#override
Widget build(BuildContext ctx) {
return Scaffold(
appBar: AppBar(
title: Text('MapSample'),
),
body: Container(
child: Column(
children: <Widget>[
Form(
key: _textKey,
child: TextFormField(
controller: controller,
validator: (str) {
myErrorString = "";
if(isLoginPressed){
isError = true;
if (str.isEmpty) {
myErrorString = 'err_empty_field';
return myErrorString;
}
else if (str.length < 10) {
myErrorString = 'err_invalid_phone';
validateMe();
return myErrorString;
}
/*else if (!_phoneRegex.hasMatch(str)) {
myErrorString = 'err_invalid_phone';
validateMe();
return myErrorString;
}*/
isError = false;
myErrorString = "";
}else{
myErrorString = "";
}
},
),
onChanged: () {
counter++;
if(counter == 9){
counter = 0;
isLoginPressed = false;
}
if(isLoginPressed){
}else{
isWriting = true;
isLoginPressed = false;
myErrorString = "";
_textKey.currentState.validate();
}
},
),
RaisedButton(
onPressed: () {
counter = 1;
isWriting = false;
isLoginPressed = true;
_textKey.currentState.validate();
},
child: Text('login'),
)
],
),
),
);
}
void validateMe() {
if(isLoginPressed){
currentPosition = TextSelection.fromPosition(
TextPosition(offset: controller.text.length));
String currentText = controller.text;
_textKey.currentState.reset();
controller.text = currentText;
controller.selection = currentPosition;
isWriting = false;
isLoginPressed = true;
}
}
}

Answer 5

I've found working and easier way
final _textKey = GlobalKey<FormState>();
final TextEditingController _controller = TextEditingController();
Widget _getPhoneInputForm() {
final RegExp _phoneRegex = RegExp(r"^\+{1}\d{10,17}");
bool isError = false;
bool isButtonPressed = false;
return Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: EdgeInsets.symmetric(horizontal: 36.0),
child: Form(
key: _textKey,
child: TextFormField(
keyboardType: TextInputType.phone,
decoration: InputDecoration(
hintText: hint_enter_phone,
contentPadding: EdgeInsets.all(24.0),
fillColor: Colors.blueGrey.withOpacity(0.3),
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(16.0)),
borderSide: BorderSide(color: Colors.blueGrey))),
controller: _controller,
validator: (str) {
if (!isButtonPressed) {
return null;
}
isError = true;
if (str.isEmpty) {
return err_empty_field;
} else if (!_phoneRegex.hasMatch(str)) {
return err_invalid_phone;
}
isError = false;
},
onFieldSubmitted: (str) {
if (_textKey.currentState.validate()) _phoneLogin();
},
),
onChanged: () {
isButtonPressed = false;
if (isError) {
_textKey.currentState.validate();
}
},
),
),
RaisedButton(
color: Colors.teal,
textColor: Colors.white,
onPressed: () {
isButtonPressed = true;
if (_textKey.currentState.validate()) _phoneLogin();
},
child: Text(login),
)
],
);
}

Answer 6

This is an exemple , i think its not necessary to do onchange() , the function validate name do the work ...
String validateName(String value) {
String patttern = r'(^[a-zA-Z ]*$)';
RegExp regExp = new RegExp(patttern);
if (value.length == 0) {
return "Name is Required";
} else if (!regExp.hasMatch(value)) {
return "Name must be a-z and A-Z";
}
return null;
}
TextFormField(
controller: _lastname, validator: validateName ,
//initialValue: widget.contact.last_name,
decoration:
InputDecoration(labelText: 'Last name'),
),
void Save() {
if (_keyForm.currentState.validate()) {
// No any error in validation
_keyForm.currentState.save();
................
}

Answer 7

i have found that using a combination of FocusNode and AtuoValidateMode.onUserInteraction does the trick.
class _TextAutoValidateModeExampleState extends State<TextAutoValidateModeExample> {
FocusNode node = FocusNode();
#override
Widget build(BuildContext context) {
return Container(
child: TextFormField(
focusNode: node,
autovalidateMode: AutovalidateMode.onUserInteraction,
validator: (value) {
if(node.hasFocus) return null;
if (value!.isEmpty) return "value cannot be empty";
if (!value.isEmail) return "not a valid email";
},
),
);
}
}

Answer 8

// Call this method inside onChanged() and when its focusnode hasFocus
void formReset(GlobalKey<FormState> formKey, TextEditingController controller) {
String stringValue = controller.text;
TextPosition textPosition = controller.selection.base;
formKey.currentState.reset();
controller.text = stringValue;
controller.selection = TextSelection.fromPosition(textPosition);
}

Answer 9

this format worked for me, Hope it helps someone....
validator: (value){
bool emailValid = RegExp(r"^[a-zA-Z0-9.a-zA-Z0-9.!#$%&'*+-/=?^_`{|}~]+#[a-zA-Z0-9]+\.[a-zA-Z]+").hasMatch(value);
isError = true;
if(value.isEmpty){
return "Provide an email";
}else if(!emailValid){
return "Enter a valid email";
}
isError = false;
return null;
},