I want to allow the user to only put maximum of 5 numbers between 1 and 10.000, but this TextFormField is not required and should not be submitted through Form validation, but I want to let the user know if he is adding this field, that he can not exceed 10.000 and he must put only numbers from 1 to 10.000. The code for the TextFormField:

TextFormField(
                                keyboardType: TextInputType.number,
                                controller: _number,
                                inputFormatters: <TextInputFormatter>[
                                  FilteringTextInputFormatter.digitsOnly //I have set this so the input is only numbers/digits
                                ],
                                decoration: kTextFieldDecoration.copyWith(
                                  hintText: 'Enter number between 1 and 10.000',
                                  labelText: 'Number from 1 to 10.000',
                                ),
                              ),

I'm not sure how to achieve this, I used regex validation for the rest of the fields, but since this field is not required, I can't validate it through Form validation. Any form of help is appreciated. Thanks in advance!

CodePudding user response：

May try the code below, for your reference https://stackoverflow.com/a/68072967/7972633

Updated version 1

class NumericalRangeFormatter extends TextInputFormatter {
  final double min;
  final double max;

  NumericalRangeFormatter({required this.min, required this.max});

  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue,
    TextEditingValue newValue,
  ) {

    if (newValue.text == '') {
      return newValue;
    } else if (int.parse(newValue.text) < min) {
      return TextEditingValue().copyWith(text: min.toStringAsFixed(5));
    } else {
      return int.parse(newValue.text) > max ? oldValue : newValue;
    }
  }
}

keyboardType: TextInputType.numberWithOptions(),
inputFormatters: [
   LengthLimitingTextInputFormatter(5) // only allow 5 digit number
],

CodePudding user response：

You can use validator for a field that is not mandatory in this way :

validator: (value) {
    if (value == null || value.isEmpty) {
      return null;
    }else {
      double? num = double.tryParse(value);
      if(num == null)
         return 'Invalid value';
      else if(num < 1 || num > 10)
         return 'Please enter value between 1 and 10.000';
    }
    return null;
},

So, in this way if value is null or empty then we can skip check otherwise perform required check.

CodePudding user response：

Please try this below regex expression

It allows only numbers between 1 to 10,000 and use you may restrict inputs using maxLength property available in TextFormField

int validateNumber(String numberVal) {
    String patttern = r'^[1-9]([0-9]{0,1})([.][0-9]{1,3})?$';
    RegExp regExp = new RegExp(patttern);
    if (numberVal.isEmpty || numberVal.length == 0) {
      return 1;
    } else if (!regExp.hasMatch(numberVal)) {
      return 2;
    } else {
      return 0;
    }
  }

TextFormField(
                    autovalidateMode: AutovalidateMode.onUserInteraction,
                    /* autovalidate is disabled */
                    controller: numController,
                    keyboardType: TextInputType.numberWithOptions(
                      decimal: true,
                    ),
                    maxLength: 6,
                    onChanged: (val) {},
                    maxLines: 1,
                    validator: (value) {
                      int res = validateNumber(value);
                      if (res == 1) {
                        return "Please fill this required field";
                      } else if (res == 2) {
                        return "Please enter valid number between 1 to 10.000";
                      } else {
                        return null;
                      }
                    },
                    focusNode: numFocus,
                    autofocus: false,
                    decoration: InputDecoration(
                      errorMaxLines: 3,
                      counterText: "",
                      filled: true,
                      fillColor: Colors.white,
                      focusedBorder: OutlineInputBorder(
                        borderRadius: BorderRadius.all(Radius.circular(4)),
                        borderSide: BorderSide(
                          width: 1,
                          color: Color(0xffE5E5E5),
                        ),
                      ),
                      disabledBorder: OutlineInputBorder(
                        borderRadius: BorderRadius.all(Radius.circular(4)),
                        borderSide: BorderSide(
                          width: 1,
                          color: Color(0xffE5E5E5),
                        ),
                      ),
                      enabledBorder: OutlineInputBorder(
                        borderRadius: BorderRadius.all(Radius.circular(4)),
                        borderSide: BorderSide(
                          width: 1,
                          color: Color(0xffE5E5E5),
                        ),
                      ),
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.all(Radius.circular(4)),
                        borderSide: BorderSide(
                          width: 1,
                        ),
                      ),
                      errorBorder: OutlineInputBorder(
                          borderRadius: BorderRadius.all(Radius.circular(4)),
                          borderSide: BorderSide(
                            width: 1,
                            color: Colors.red,
                          )),
                      focusedErrorBorder: OutlineInputBorder(
                        borderRadius: BorderRadius.all(Radius.circular(4)),
                        borderSide: BorderSide(
                          width: 1,
                          color: Colors.red,
                        ),
                      ),
                      hintText: "Enter number between 1 to 10.000" ?? "",
                    ),
                  ),