feat: Implement UIScene lifecycle for iOS

[Srishtyshree]

feat: Implement UIScene lifecycle for iOS

Summary

This PR implements UIScene lifecycle support for React Native on iOS, resolving the warning: CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version.

Fixes #54739

Problem

Starting with iOS 13, Apple introduced the UIScene lifecycle to support multi-window applications and better separate UI concerns from application-level concerns. React Native's RCTAppDelegate currently doesn't support this modern lifecycle, causing a warning that Apple has indicated will eventually become an assertion (app crash) in future iOS versions.

Solution

This PR adds UIScene lifecycle support to RCTAppDelegate while maintaining backward compatibility:

Changes Made

1. Modified RCTAppDelegate.h

• Added application:configurationForConnectingSceneSession:options: method declaration
• Method is marked with API_AVAILABLE(ios(13.0)) for backward compatibility

2. Modified RCTAppDelegate.mm

• Implemented UIScene configuration method
• Returns a UISceneConfiguration that specifies RCTSceneDelegate as the scene delegate class

3. Created RCTSceneDelegate.h

• New scene delegate class conforming to UIWindowSceneDelegate
• Marked with API_AVAILABLE(ios(13.0))
• Manages the window property for the scene

4. Created RCTSceneDelegate.mm

• Implements UIScene lifecycle methods:
  • scene:willConnectToSession:options: - Sets up the window and React Native root view
  • sceneDidDisconnect: - Handles scene disconnection
  • sceneDidBecomeActive: - Scene activation handling
  • sceneWillResignActive: - Scene deactivation handling
  • sceneWillEnterForeground: - Foreground transition
  • sceneDidEnterBackground: - Background transition
• Integrates with existing RCTAppDelegate to access RCTReactNativeFactory and RCTRootViewFactory

5. Updated RNTester/Info.plist

• Added UIApplicationSceneManifest configuration
• Demonstrates proper UIScene setup for React Native apps

Key Design Decisions

1. Backward Compatibility: All UIScene-related code is guarded with API_AVAILABLE(ios(13.0)), ensuring apps targeting iOS < 13 continue to work.

2. Opt-in Approach: UIScene support is activated only when apps include the UIApplicationSceneManifest in their Info.plist. Existing apps without this configuration continue using the traditional app delegate lifecycle.

3. Integration with Existing Architecture: The RCTSceneDelegate accesses the app delegate to retrieve the RCTReactNativeFactory, maintaining consistency with the existing React Native initialization flow.

4. No Breaking Changes: Existing apps using RCTAppDelegate without UIScene configuration will continue to work exactly as before.

Testing

Manual Testing Performed

1. ✅ RNTester with UIScene: Built and ran RNTester with UIScene manifest - app launches successfully, no warnings
2. ✅ Backward Compatibility: Verified that removing UIScene manifest still works (traditional lifecycle)
3. ✅ Scene Lifecycle Events: Tested app backgrounding, foregrounding, and scene transitions

Expected Behavior

Before this PR:

• Warning in Xcode console: CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle

After this PR:

• No warning when UIApplicationSceneManifest is present in Info.plist
• App properly adopts UIScene lifecycle on iOS 13+
• Existing apps without UIScene manifest continue working as before

Migration Guide for Users

For New Apps

Include the following in your Info.plist:

<key>UIApplicationSceneManifest</key>
<dict>
    <key>UIApplicationSupportsMultipleScenes</key>
    <false/>
    <key>UISceneConfigurations</key>
    <dict>
        <key>UIWindowSceneSessionRoleApplication</key>
        <array>
            <dict>
                <key>UISceneConfigurationName</key>
                <string>Default Configuration</string>
                <key>UISceneDelegateClassName</key>
                <string>RCTSceneDelegate</string>
            </dict>
        </array>
    </dict>
</dict>

For Existing Apps

Option 1: Adopt UIScene (Recommended for iOS 13+)

• Add the UIApplicationSceneManifest configuration above to your Info.plist
• No code changes required if using RCTAppDelegate

Option 2: Continue with Traditional Lifecycle

• No changes needed
• App will continue working as before
• Warning will persist but can be ignored for now

Changelog

[iOS] [Added] - Implement UIScene lifecycle support for iOS 13+

Additional Notes

• The RCTAppDelegate class is marked as deprecated in favor of RCTReactNativeFactory, but this PR adds UIScene support to maintain compatibility for existing users
• The podspec (React-RCTAppDelegate.podspec) automatically includes new .h and .mm files via podspec_sources, so no podspec changes were needed
• All UIScene APIs are properly guarded with availability checks

Screenshots

UIScene lifecycle adopted successfully - no warnings in Xcode console

---

Reviewers: @cipolleschi @huntie @cortinico

Please let me know if you'd like any changes to this implementation or if you prefer a different approach!

[react-native-bot]

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