didChange method
Updates this field's state to the new value. Useful for responding to child widget changes, e.g. Slider's Slider.onChanged argument.
Triggers the Form.onChanged callback and, if the Form.autovalidate field is set, revalidates all the fields of the form.
Implementation
void didChange(T value) {
setState(() {
_value = value;
});
Form.of(context)?._fieldDidChange();
}