Question

I have a view with multiple dynamically created UITextfields and UISegmented controls on it (but for purposes of this question, there could also be UIButtons, UISwitches, UISliders, or anything else that inherits from UIControl). I want to preform an action whenever the user finished interacting with any of the controls, regardless of what subclass of control it belongs to. From looking at other questions, I think I want to use addTarget:action:forControlEvents: to add observers to each of my controls after they are created, but I don’t know which event I’m looking for. I’ve tried all the ones that are listed in the Apple Docs here that seemed relevant but none of them seem to be triggered everytime. I’m looking for something like .LostFocus in VBA, but I can’t seem to find out what that is – I know there is a becomeFirstResponder method to make a control active, but I can’t find anything like a “lostFirstResponder” event.

I suppose I could use isKindOfClass to tell what kind of control it is, and set up my event accordingly, but that seems a little sloppy and I feel like there should be a more direct way to do it. I could also probably set up a UITapGestureRecognizer and build up something that way, but that still feels like a workaround and not really the way it’s supposed to be done.

Answer 1

If you’re willing to subclass, you can override -resignFirstResponder to detect lost “focus”, and act accordingly. This is probably only useful for things like textfields which can hold first responder status, and would not work for UISwitch for instance.

Since all UIControl objects are just UIViews, you can also override touchesEnded to detect the end of interaction with these elements.. although the more accepted way is to add your dismissal handler method as an action for all the UIControlEvents that indicate end of interaction, or just UIControlEventValueChanged.

More info on UIResponder here from Apple’s Documentation:

https://developer.apple.com/library/ios/documentation/uikit/reference/UIResponder_Class/Reference/Reference.html#//apple_ref/occ/instm/UIResponder/resignFirstResponder

Many UIKit classes have delegate methods that indicate when interactions have ended, for instance UITextField has a textFieldDidEndEditing method. UITextView has similar methods.