AccessibilityFocusState

Overview 概要

Use this capability to request that VoiceOver or other accessibility technologies programmatically focus on a specific element, or to determine whether VoiceOver or other accessibility technologies are focused on particular elements. Use accessibilityFocused(_:equals:) or accessibilityFocused(_:) in conjunction with this property wrapper to identify accessibility elements for which you want to get or set accessibility focus. When accessibility focus enters the modified accessibility element, the framework updates the wrapped value of this property to match a given prototype value. When accessibility focus leaves, SwiftUI resets the wrapped value of an optional property to nil or the wrapped value of a Boolean property to false. Setting the property’s value programmatically has the reverse effect, causing accessibility focus to move to whichever accessibility element is associated with the updated value.

In the example below, when notification changes, and its isPriority property is true, the accessibility focus moves to the notification Text element above the rest of the view’s content:

struct CustomNotification: Equatable {
    var text: String
    var isPriority: Bool
}


struct ContentView: View {
    @Binding var notification: CustomNotification?
    @AccessibilityFocusState var isNotificationFocused: Bool


    var body: some View {
        VStack {
            if let notification = self.notification {
                Text(notification.text)
                    .accessibilityFocused($isNotificationFocused)
            }
            Text("The main content for this view.")
        }
        .onChange(of: notification) { notification in
            if (notification?.isPriority == true)  {
                isNotificationFocused = true
            }
        }


    }
}

To allow for cases where accessibility focus is completely absent from the tree of accessibility elements, or accessibility technologies are not active, the wrapped value must be either optional or Boolean.

Some initializers of AccessibilityFocusState also allow specifying accessibility technologies, determining to which types of accessibility focus this binding applies. If you specify no accessibility technologies, SwiftUI uses an aggregate of any and all active accessibility technologies.