每当打开应用程序时，SwiftUI AppDelegate 都不会运行

Question

这是我制作的一个简单的AppDelegate：

import SwiftUI

class AppDelegate: UIResponder, UIApplicationDelegate {

    private func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {
        print("application")
        // first launch
        // this method is called only on first launch when app was closed / killed
        return true
    }

    private func applicationWillEnterForeground(application: UIApplication) -> Bool{
        print("applicationWillEnterForeground")
        // app will enter in foreground
        // this method is called on first launch when app was closed / killed and every time app is reopened or change status from background to foreground (ex. mobile call)
        return true
    }

    private func applicationDidBecomeActive(application: UIApplication) -> Bool {
        print("applicationDidBecomeActive")
        // app becomes active
        // this method is called on first launch when app was closed / killed and every time app is reopened or change status from background to foreground (ex. mobile call)
        return true
    }
}

@main
struct CouponDeckApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    @Environment(\.scenePhase) private var scenePhase
    var body: some Scene {
        WindowGroup {
            AppContentView()
                
        }
    }
}

不过，AppDelegate 似乎没有调用它的任何函数。它应该在 3 个地方运行它们，但没有一个在运行。为什么会发生这种情况，我该如何解决？

Answer 1

您已使用 @main 标记您的应用程序，这使其成为应用程序入口点。

并非所有应用委托的方法都适用于UIApplicationDelegateAdaptor，就像这里的applicationWillEnterForeground applicationDidBecomeActive 不会被调用。

相反，您应该在 SwiftUI 视图中使用发布者，如下所示：

.onReceive(NotificationCenter.default.publisher(for: UIApplication.didBecomeActiveNotification)) { _ in
    print("applicationDidBecomeActive")
}
.onReceive(NotificationCenter.default.publisher(for: UIApplication.willEnterForegroundNotification)) { _ in
    print("applicationWillEnterForeground")
}

您的AppDelegate 的另一个问题是它没有所需的方法签名。当你添加新方法时，不要从某个地方粘贴它，而是从方法名称中输入几个字母，然后让 Xcode 完成其余的工作。在您的情况下，如果您的签名正确，private 将是 Xcode 报告的错误。

如果您出于某种原因仍想将它们放入您的委托中，您需要将 @main 移动到 AppDelegate，并使用 UIHostingController 初始化您的 SwiftUI 视图，就像在 SwiftUI 1 中所做的那样：

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        let window = UIWindow()
        self.window = window
        window.rootViewController = UIHostingController(rootView: ContentView())
        window.makeKeyAndVisible()
        return true
    }
    
    func applicationWillEnterForeground(_ application: UIApplication) {
        print("applicationWillEnterForeground")
    }
    
    func applicationDidBecomeActive(_ application: UIApplication) {
        print("applicationDidBecomeActive")
    }
}

另外你需要更新Info.plist，设置启用多个窗口为NO：