Introduction:

With iOS 13.0, Apple introduced a number of changes in how its UIKit framework operates, including the deprecation of keyWindow. This change has caused some confusion among developers, especially those maintaining legacy codebases. This article will guide you through understanding why keyWindow was deprecated and how to adapt your applications to utilize modern alternatives.

Understanding keyWindow and its Deprecation

The keyWindow property was traditionally used in iOS applications to reference the window that is currently receiving input events. It essentially identifies the active window within the app. However, with iOS 13.0, Apple deprecated this property for several reasons:

1. Multiple Windows Support: With the introduction of multi-window support on iPad, an iOS application can now have more than one active window. This development necessitated a way to manage multiple windows more effectively.
2. Better API Design: Apple aims to encourage a move towards using newer APIs that provide a clearer and more explicit management of scenes and windows.

The deprecation doesn't mean your apps will break immediately, but Apple encourages developers to adopt newer APIs to future-proof applications.

Transitioning to UIWindowScene

Understanding UIWindowScene

With the deprecation of keyWindow, Apple's preferred approach is UIWindowScene, introduced in iOS 13.0. A UIWindowScene manages one or more windows for a specific instance of your app's user interface.

Adopting UIWindowScene in Your App

To properly implement UIWindowScene, you will need to perform a few key changes to your app's structure, particularly in the App Delegate and Scene Delegate classes:

1. Implement Scene Delegate: By adopting the new scene life cycle, you can manage scenes and windows effectively. With this setup, your app is better organized to handle multiple windows.
2. Fetch Windows from Scene: Use UIWindowScene to identify and fetch your app's windows:

1   if let windowScene = (UIApplication.shared.connectedScenes.first as? UIWindowScene) {
2       if let keyWindow = windowScene.windows.first(where: { $0.isKeyWindow }) {
3           // Proceed with the keyWindow
4       }
5   }

1. Configuration Changes in Info.plist: You'll need to add or update the UIApplicationSceneManifest key in your Info.plist to specify the scenes your app uses.

Example Transition

Here is an example of transitioning from keyWindow:

Before (Using keyWindow):

let window = UIApplication.shared.keyWindow

After (Using UIWindowScene):

1if let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene {
2    if let window = windowScene.windows.first {
3        // Use the window
4    }
5}

Common Issues and Troubleshooting

Developers may encounter various issues when transitioning from keyWindow to UIWindowScene. Here are some common challenges and resolutions:

• Null Reference Errors: Ensure that you are safely accessing windows within their proper life cycle events, such as sceneWillEnterForeground or sceneDidBecomeActive.
• Compatibility Issues: For apps that must support both the pre-iOS 13 method and the new scene-based method, consider using version checks to handle compatibility:

1  if #available(iOS 13.0, *) {
2      // Use UIWindowScene
3  } else {
4      // Use legacy keyWindow approach
5  }

Summary

Below is a table summarizing the key changes and recommendations for transitioning from keyWindow:

By migrating to UIWindowScene, developers can leverage new functionalities and ensure their applications remain robust across future iOS releases. As best practices evolve, adopting these changes will keep applications working seamlessly with improved code architecture and functionality.

Conclusion

Apple's deprecation of keyWindow opens the door for better window and scene management within iOS applications. With careful attention to the new UIWindowScene API, your applications can adapt to modern iOS environments, allowing for an enriched user experience and easier maintenance. Implementing these changes could require some refactoring efforts, but the long-term benefits of adopting Apple's latest frameworks are substantial.