Use touch events directly on a view subclass if touch handling is intricately linked to the view's content.
If you don't plan to use gesture recognizers with a custom view, you can handle touch events directly from the view itself. Because views are responders, they can handle Multi-Touch events and many other types of events. When UIKit determines that a touch event occurred in a view, it calls the view’s
touches method. You can override these methods in your custom views and use them to provide a response to touch events.
The methods you override in your views (or in any responder) to handle touches correspond to different phases of the touch event–handling process. For example, Figure 1 illustrates the different phases of a touch event. When a finger (or Apple Pencil) touches the screen, UIKit creates a
UITouch object, sets the touch location to the appropriate point, and sets its
phase property to
UITouch. When the same finger moves around the screen, UIKit updates the touch location and changes the
phase property of the touch object to
UITouch. When the user lifts the finger from the screen, UIKit changes the
phase property to
UITouch and the touch sequence ends.
Similarly, the system may cancel an ongoing touch sequence at any time; for example, when an incoming phone call interrupts the app. When it does, UIKit notifies your view by calling the
touches method. You use that method to perform any needed cleanup of your view’s data structures.
UIKit creates a new
UITouch object for each new finger that touches the screen. The touches themselves are delivered with the current
UIEvent object. UIKit distinguishes between touches originating from a finger and from Apple Pencil, and you can treat each of them differently.