currentValueLength property
The current number of characters that have been entered into an editable text field.
For the purpose of this function a character is defined as one Unicode scalar value.
This should only be set when isTextField is true. Must be set when maxValueLength is set.
Implementation
int? get currentValueLength => _currentValueLength;Implementation
set currentValueLength(int? value) {
  if (value == currentValueLength) {
    return;
  }
  _currentValueLength = value;
  _hasBeenAnnotated = true;
}