Take your iPad apps to the next level

Scene Overview

Configuration

The structure of a scene’s components is defined by a scene configuration.

• defines scene role and delegate class

• optional attributes:

  • name

  • storyboard

  • UIScene subclass

• Can be declared either in the Info.plist or can be created at runtime

Content

• represented by an NSUserActivity

• These activities are used for requesting scenes as well as for state restoration

Scene management

• managed by a scene delegate

• the delegate is responsible for:

  • setting up the UI

  • responding to lifecycle events

  • saving and restoring state.

Scene tracking

• tracked by UISceneSession

• scenes can be disconnected and reconnected by the system when it’s in the background

• the scene session tracks the scene regardless of its connection state and persists between (scene) launches

A scene session can be thought of as the representation in the system app switcher:
Each item in the switcher corresponds to a scene session.

Scene request options

When requesting a scene from the system, you can provide an options object for customizing the request.

• new in iPadOS 15, UIWindowScene.ActivationRequestOptions offers new options subclass specifically for window scenes

• Using this subclass allows you to specify a presentation style (UIWindowScene.PresentationStyle (.prominent, .standard, .automatic)

Prominent presentation

• new style

• presented modally in the current workspace with the scenes behind it dimmed.

• this presentation should provide Cancel, Close, or Done buttons

• can be re-positioned like any other scene

• this presentation should be dedicated to specific content within your app like a document or file.

• this dedicated content scope must be defined in the scene’s activation conditions (UISceneActivationConditions)

Window scene activation action

• UIWindowScene.ActivationAction

• to be used in menus, buttons, and bar button items

• defaults to prominent style

• provides title and image

let newSceneAction = UIWindowScene.ActivationAction({ _ in

  // Create the user activity that represents the new scene content.
  let userActivity = NSUserActivity(activityType: "com.myapp.detailscene")

  // Return the activation configuration.
  return UIWindowScene.ActivationConfiguration(userActivity: userActivity)
})

// Add the action to the menu.
let menu = UIMenu(children: [
  newSceneAction,
  flagAction,
  shareAction
])

• on iPhone this action is automatically hidden

• an alternate action can be provided on the ActivationAction initialization

Open scenes via gesture

• requires prominent style

Two ways:

1. new UICollectionViewDelegate method

func collectionView(
  _ collectionView: UICollectionView,
  sceneActivationConfigurationForItemAt indexPath: IndexPath,
  point: CGPoint
) -> UIWindowScene.ActivationConfiguration? {

  // Get the item's user activity.
  guard let itemActivity = <#User Activity#> else {
    // Return nil if item can’t be opened in a dedicated scene.
    return nil
  }

  // Return the activation configuration.
  return UIWindowScene.ActivationConfiguration(userActivity: itemActivity)
}

1. UIWindowScene.ActivationInteraction

// Create an activation interaction.
let newSceneInteraction = UIWindowScene.ActivationInteraction { interaction, point in
  // Get the activity for specific point in view.
  guard let userActivity = <#User Activity#> else { return nil }

  // Return an activation configuration.
  return UIWindowScene.ActivationConfiguration(userActivity: userActivity)

} errorHandler: { error in
  // Present the content in another manner.
  <#Present Content#>
}

// Add interaction to the view.
<#View#>.addInteraction(newSceneInteraction)

QLPreviewSceneActivationConfiguration

• QLPreviewSceneActivationConfiguration

• special scene for displaying files

• system-managed (no need for delegate, or callbacks to worry about)

Scene state restoration

• can restore interaction states of textfields via new interactionState property

• New in iPadOS 15, there’s a new callback dedicated to state restoration

• scene(_:restoreInteractionState:)

• called after the scene is connected and the storyboard has been loaded, but before the first transition to foreground

Extending state restoration

• iPadOS 15 allows your app to request a short-term extension

• During this extension, the launch image will remain visible while still allowing the main RunLoop to execute

• app must signal when complete (app will be terminated otherwise)

func scene(_ scene: UIScene, restoreInteractionState stateRestorationActivity: NSUserActivity) {
  guard let viewController = window?.rootViewController as? <#Expected View Controller Class#> else { return }

  // Request an extension.
  scene.extendStateRestoration()

  // Fetch content asynchronously.
  <#self.someAsyncFunction#> { result in
    <#Restore Content#>

    // Signal that state has been restored.
    scene.completeStateRestoration()
  }
}

Keyboard shortcuts

• On iPadOS 15, the Mac Catalyst menu system will show as the new shortcut interface

• hold down the Command key (in an external keyboard) to display this menu

• disabled commands are hidden in iPadsOS

• includes all system commands (undo/redo included)

• to customize this, override the buildMenu(with:) app delegate function

Pointer enhancements

Multiple items selection

• new UIBandSelectionInteraction to select multiple items on iPad (you get this for free if you’re using a collection view)

// Support multi-selection using UIBandSelectionInteraction.

let selectionInteraction = UIBandSelectionInteraction { [weak self] interaction in
  guard let strongSelf = self else { return }
          
  // Handle selection by responding to interaction state.
  if interaction.state == .selecting {
    strongSelf.selectItemsInRect(interaction.selectionRect)
  } 
  else if interaction.state == .ended {
    strongSelf.finalizeSelection()
  }
}

view.addInteraction(selectionInteraction)

• can further select and deselect items by looking at the initialModifierFlags UIBandSelectionInteraction property

Pointer accessories

• ability to attach accessories to system pointers

• provide contextual hints by combining secondary shapes with the primary pointer

• accessories are visually separate and secondary to the main pointer

• rendered differently than the main pointer, have separate animation

• can be combined with any pointer style

Pointer latching

• iPadOS 15 introduces the concept of latchingAxes on UIPointerRegion

• e.g. a horizontally latching region lets you drag freely along the x-axis while still rubberbanding along the y-axis