registerOnTouched method
Set the function to be called when the control is touched.
A control's touched state is most commonly used to determine whether or not to show a validation error (for example, many forms would not want to show a required field as having an error before it's been interacted with).
Idiomatically, the control is considered touched once it has received a blur event. Certain controls, such as a dropdown select, may want to consider the control as touched if the user has opened and then closed the list of options.
See TouchHandler
for the default idiomatic implementation.
Implementation
@override
void registerOnTouched(_) {}