UIKit Modernization

Guidance for the scene-based life cycle and resizability changes that UIKit requires in the iOS 27 cycle — the highest-impact UIKit change in years, because it gates whether your app launches at all.

When to Use

Use this skill when:

• Building against the iOS 27 SDK and your app uses only a UIApplicationDelegate (no scene delegate)
• Your app "won't launch" after updating to the latest SDK
• Making an iPhone app adapt to arbitrary window sizes (iPhone Mirroring on Mac, iPhone apps on iPad)
• Replacing UIScreen.main, interface idiom, or orientation checks with adaptive equivalents
• Adopting iOS 27 additive APIs — tab bar sidebar/prominent tab, nav bar minimization, menu image visibility, CoreMotion/CoreLocation Body protocols
• Fixing behavior that breaks in iPhone Mirroring — dead custom gestures, failing Face ID prompts, layouts stuck in portrait
• Adding pointer effects (UIPointerInteraction) or hardware-keyboard commands (UIKeyCommand, the hold-⌘ HUD) to a UIKit app
• Planning a UIKit → scene-lifecycle migration

Example Prompts

• "My UIKit app won't launch on iOS 27"
• "How do I adopt the scene-based life cycle?"
• "What replaces UIScreen.main?"
• "How do I make my iPhone app resizable?"
• "How do I set a minimum window size or lock orientation on iOS 27?"
• "Should I use the interface idiom or size classes for layout?"
• "How do I put a tab bar in a sidebar on iPhone? (iOS 27)"
• "My custom pinch gesture stops working in iPhone Mirroring"
• "Why does Face ID fail when my app runs through iPhone Mirroring?"
• "My UIKeyCommand doesn't show in the iPad hold-Command HUD"
• "What goes in UIApplicationSceneManifest for a single-window app?"
• "What should I clean up in sceneDidDisconnect?"
• "How do I open a new window from UIKit code?"
• "How do I let users drag an item out to open it as a new window on iPad?"
• "Cmd-Z in one window undoes edits made in another window"
• "How do I disable Scribble on one text field?"
• "Why was my upload rejected for a missing launch screen?"
• "What's the View Annotations API for Siri?"

What This Skill Provides

• The scene-lifecycle requirement at iOS 27 (apps without a UISceneDelegate no longer launch) and the migration path
• Info.plist configuration – the UIApplicationSceneManifest structure, the launch-screen key validated at upload on the 27 SDK (TN3208), and destinations-vs-device-checks
• Scene lifecycle edges – sceneDidDisconnect teardown semantics, UISceneSessionActivationRequest window opening, drag-to-create-window (drag items carrying an NSUserActivity, gated on NSUserActivityTypes), per-window undo scoping, per-scene NSUserActivity restoration, external-display scene roles, and the displayGamut/legibilityWeight/activeAppearance traits
• A don't/do table for replacing UIScreen.main, screen.scale, screen.bounds, idiom, and orientation with scene/trait/size-class equivalents
• The new iOS 27 additive APIs — prominentTabIdentifier, UITabBarControllerSidebar.preferredPlacement, navigationBarMinimization, UIMenuElement.preferredImageVisibility, deviceMotionBody/headingBody
• iPhone Mirroring compatibility – the always-portrait orientation trap, indirect trackpad/mouse input reaching custom gesture recognizers (UIApplicationSupportsIndirectInputEvents, scroll-type masks), companion Face ID approval on the Mac (iOS 18), and cross-device drag and drop
• Desktop-class input – UIPointerInteraction pointer effects, UIHoverGestureRecognizer, UIKeyCommand with discoverabilityTitle for the hold-⌘ shortcut HUD, and Scribble (UIScribbleInteraction / UIIndirectScribbleInteraction) for Pencil handwriting
• Apple Intelligence touchpoints (menu "Ask Siri", View Annotations, drag-and-drop resource loading)
• How to let Xcode 27's app-modernization agent do the mechanical rewrites

Related

• UIKit-SwiftUI Bridging – embedding SwiftUI in a modernized scene-based UIKit app
• App Composition – app-level integration and UIKit → SwiftUI migration priority
• SwiftUI Layout – size-class-driven adaptive layout, the recommended replacement for idiom/orientation checks