Tells the delegate that a focus update occurred.
- iOS 9.0+
- tvOS 9.0+
The collection view object notifying you of the focus change.
The context object containing metadata associated with the focus change. This object contains the index path of the previously focused item and the currently focused item.
The animation coordinator to use when creating any additional animations.
The collection view calls this method when a focus-related change occurs. You can use this method to update your app’s state information or to animate changes to your app’s visual appearance.
If you subclass
UICollection, you can also implement the same behavior by overriding the
did method, which is defined by the
UIFocus protocol and adopted by all views.