Getting Null check operator used on a null value error when calling in flutter

Question

I am using this dart package otp_text_field 1.1.1.

                     OTPTextField(
                        length: 6,
                        width: MediaQuery.of(context).size.width,
                        fieldWidth: 30,
                        style: TextStyle(fontSize: 20),
                        textFieldAlignment: MainAxisAlignment.spaceAround,
                        fieldStyle: FieldStyle.underline,
                        onChanged: (pin) {
                          if (pin.length == 6) {
                            print("Changed: " + pin);
                          }
                        },
                      )

I get this error on the onChanged handler

The following _CastError was thrown while calling onChanged:
Null check operator used on a null value
When the exception was thrown, this was the stack

Not getting any idea on whats wrong.

Added Stacktrace -

  _OTPTextFieldState.buildTextField.<anonymous closure>
package:otp_text_field/otp_field.dart:179
#1      EditableTextState._formatAndSetValue
package:flutter/…/widgets/editable_text.dart:2298
#2      EditableTextState.updateEditingValue
package:flutter/…/widgets/editable_text.dart:1749
#3      TextInput._handleTextInputInvocation
package:flutter/…/services/text_input.dart:1351
#4      MethodChannel._handleAsMethodCall
package:flutter/…/services/platform_channel.dart:435

It seems the problem relies inside the package. Can you share the stacktrace (the lines below "this was the stack")? — enzo
– enzo, Commented Jul 16, 2021 at 23:35
Also if I use onCompleted handler with onChanged I dont see any errors — Sumchans
– Sumchans, Commented Jul 16, 2021 at 23:45
Yes, the stacktrace points to this line in the package's source code. It only raises when onCompleted is null (i.e. you don't pass it as parameter). A related issue. — enzo
– enzo, Commented Jul 16, 2021 at 23:46

Petrus Nguyễn Thái Học · Accepted Answer · 2021-12-31 09:24:45Z

2

onChanged: (String? pin) {
  if (pin?.length == 6) { }
}

answered Dec 31, 2021 at 9:24

Petrus Nguyễn Thái Học

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Comments

Eric Aya · Accepted Answer · 2021-12-31 13:39:04Z

0

Just provide the onCompleted callback to that widget. It is a nullable callback which means its not mandatory to pass that function. But this dependencies call this callback if the length of the top text field matches with the specified length you had provided.

edited Dec 31, 2021 at 13:39

Eric Aya

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answered Dec 31, 2021 at 9:22

Naveen Kumar. L

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