UIResponder in iOS

Flashcards about UIResponder in iOS

What is UIResponder in iOS?

UIResponder is an abstract base class for objects that respond to and handle events in iOS. It is the superclass of many UIKit classes, including UIView, UIViewController, and UIApplication.

Which classes inherit from UIResponder?

Common subclasses include UIApplication, UIView, UIViewController, and UIWindow.

What kind of events can UIResponder handle?

UIResponder can handle touch, motion, remote control, and press events.

What method is called when a touch begins on a view?

The method is touchesBegan(_:with:).

How does UIResponder handle the event chain?

If a UIResponder cannot handle an event, it passes the event to the next responder in the responder chain.

What is the responder chain?

The responder chain is a hierarchy of responder objects (UIResponder instances) that have the opportunity to respond to events.

Can you override UIResponder methods in custom views?

Yes, you can override methods like touchesBegan, touchesMoved, touchesEnded, etc., in your custom UIView subclass.

How do UIResponder and gesture recognizers work together?

Gesture recognizers can work alongside UIResponder by detecting gestures and calling associated action methods. Gesture recognizers can prevent or delay touches from being delivered to UIResponder methods.

What happens if both a gesture recognizer and touchesBegan are implemented?

By default, gesture recognizers receive touches before the UIResponder methods. You can control interaction by setting the cancelsTouchesInView property.

How to pass an event to the next responder?

You simply do not handle the event in the current responder, and iOS automatically forwards it to the next responder in the chain.