enabled property Null safety
Whether the object currently returned by toPrimitives should be included in the restoration state.
When this returns false, no information is included in the restoration data for this property and the property will be initialized to its default value (obtained from createDefaultValue) the next time that restoration data is used for state restoration.
Whenever the value returned by this getter changes, notifyListeners must be called. When the value changes from true to false, the information last retrieved from toPrimitives is removed from the restoration data. When it changes from false to true, toPrimitives is invoked to add the latest restoration information provided by this property to the restoration data.
bool get enabled => true;