Handling Double Taps from Apple Pencil

You can use Pencil interactions to allow users to access functionality in your app quickly. Double-tapping the Apple Pencil lets the user perform actions such as switching between drawing tools without moving the Pencil to another location on the screen.

To handle double taps from Apple Pencil in your app, create a UIPencilInteraction object and set its delegate to an object that implements the UIPencilInteractionDelegate protocol. Finally, add the interaction to your app’s view, as in Listing 1.

let pencilInteraction = UIPencilInteraction()
pencilInteraction.delegate = self
view.addInteraction(pencilInteraction)

The delegate receives the double tap event when the user double-taps their Pencil. It implements the pencilInteractionDidTap(_:) method, which the system calls after the user double-taps the Apple Pencil.

In your implementation of this method, decide whether to perform the action selected by the user in the Settings app, or perform an alternative behavior that’s suitable for your app. When possible, perform the user’s preferred action.

Taking this step allows you to provide a consistent user experience across apps that support Pencil interactions. To check the user’s preferred action, use the preferredTapAction class property on UIPencilInteraction, as in Listing 2.

func pencilInteractionDidTap(_ interaction: UIPencilInteraction) {
    if UIPencilInteraction.preferredTapAction == .switchPrevious {
        leftRingControl.switchToPreviousTool()
    }
}

Should you decide not to support the preferred action, provide an intuitive way to let the user know what will happen when they double-tap the Pencil, and give them the option to disable this action.