SwiftUI中如何为AppDelegate添加可访问的UIWindow属性？

方案1：直接通过自定义AppDelegate实例访问window #

你已经通过@UIApplicationDelegateAdaptor持有了自定义MyAppDelegate的实例，可直接在App结构体或其他场景中通过该实例访问window：

@main
struct YourApp: App {
    @UIApplicationDelegateAdaptor(MyAppDelegate.self) var appDelegate
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .onAppear {
                    // 直接访问自定义delegate的window
                    let targetWindow = appDelegate.window
                }
        }
    }
}

class MyAppDelegate: NSObject, UIApplicationDelegate {
    var window: UIWindow?
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // 按需初始化window
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.rootViewController = UIHostingController(rootView: ContentView())
        window?.makeKeyAndVisible()
        return true
    }
}

方案2：让UIApplication.shared.delegate.window可访问自定义window #

如果必须通过UIApplication.shared.delegate.window访问，可通过关联对象给UIApplicationDelegate扩展window属性，并在自定义MyAppDelegate中同步赋值：

// 扩展UIApplicationDelegate，添加关联的window属性
private var windowAssociatedKey: UInt8 = 0
extension UIApplicationDelegate {
    var window: UIWindow? {
        get {
            objc_getAssociatedObject(self, &windowAssociatedKey) as? UIWindow
        }
        set {
            objc_setAssociatedObject(self, &windowAssociatedKey, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }
}

class MyAppDelegate: NSObject, UIApplicationDelegate {
    var window: UIWindow?
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.rootViewController = UIHostingController(rootView: ContentView())
        window?.makeKeyAndVisible()
        
        // 将自定义window同步到shared delegate的window属性
        application.delegate?.window = window
        return true
    }
}

补充说明 #

在iOS 13+的SwiftUI生命周期中，官方推荐使用WindowGroup或Scene相关API管理窗口，而非传统AppDelegate的window属性。如果你的需求是兼容旧逻辑或特殊场景，上述方案可解决问题。

内容的提问来源于stack exchange，提问作者Nataliia.dev