formatEditUpdate method

@override TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue)

Called when text is being typed or cut/copy/pasted in the EditableText.

You can override the resulting text based on the previous text value and the incoming new text value.

When formatters are chained, oldValue reflects the initial value of TextEditingValue at the beginning of the chain.

Implementation

@override
TextEditingValue formatEditUpdate(
  TextEditingValue oldValue,
  TextEditingValue newValue,
) {
  // We want to format the input as 'xxxx xxxx xxxx'
  String newText = newValue.text;
  // Remove all non-numeric characters from the input value
  String cleanedValue = newText.replaceAll(RegExp(r'[^0-9]'), '');
  // Add space after every four characters
  String formattedValue = cleanedValue.replaceAllMapped(
      RegExp(r".{4}"), (match) => "${match.group(0)} ");

  if (formattedValue.length >= 14) {
    formattedValue = formattedValue.substring(0, 14);
  } else {
    formattedValue =
        formattedValue.trim().substring(0, formattedValue.trim().length);
  }
  return TextEditingValue(
    text: formattedValue,
    selection: TextSelection.fromPosition(
      TextPosition(offset: formattedValue.length),
    ),
  );
}