支持iOS13時，SwiftUI應用程式無法運行

當部署目標為 15.2 時，應用程式運行良好，但后來我需要將部署目標更改為 iOS 13 以支持更多設備。Thread 1: signal SIGABRT在 iOS 14 上仍然可以正常作業，但是當它在模擬器上的 iOS 13 上運行時會崩潰并出現例外。控制臺不顯示除錯資訊：

CoreSimulator 802.6 - Device: iPhone 11 (iOS 13.0) (6CCC2B89-002B-4E83-8175-C244984BFC46) - Runtime: iOS 13.0 (17A577) - DeviceType: iPhone 11
Message from debugger: Terminated due to signal 9

以下是 WeatherApp.swift 檔案代碼的相關部分以及錯誤截圖：

@main
struct WeatherAppWrapper {
    static func main() {
        if #available(iOS 14.0, *) {
            WeatherApp.main()
        }
        else {
            UIApplicationMain(CommandLine.argc, CommandLine.unsafeArgv, nil, NSStringFromClass(SceneDelegate.self))
        }
    }
}

struct WeatherApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    @StateObject var loginStatus = UserLoginStatus()
    
    @available(iOS 14.0, *)
    var body: some Scene {
        WindowGroup {
            NavigationView{
                if Methods.UserAccount.getFromUserDefaults()["username"] != nil {
                    MainView(loggedIn: $loginStatus.loggedIn)
                    LoginView(username: "", password: "", loggedIn: $loginStatus.loggedIn)
                } else {
                    LoginView(username: "", password: "", loggedIn: $loginStatus.loggedIn)
                    MainView(loggedIn: $loginStatus.loggedIn)
                }
            }
        }
    }

    class AppDelegate: NSObject, UIApplicationDelegate, UNUserNotificationCenterDelegate, MessagingDelegate {
        func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

            //Some app-specific setup code
            ...
            
            return true
        }
        
    }
}

class UserLoginStatus: ObservableObject {
    @Published var loggedIn: Bool {
        didSet {
            print("The value of loggedIn changed from \(oldValue) to \(loggedIn)")
        }
    }
    
    init () {
        loggedIn = false
    }
}

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    @StateObject var loginStatus = UserLoginStatus()

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let mainView = MainView(loggedIn: $loginStatus.loggedIn)
        let loginView = LoginView(username: "", password: "", loggedIn: $loginStatus.loggedIn)

        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            
            if Methods.UserAccount.getFromUserDefaults()["username"] != nil {
                window.rootViewController = UIHostingController(rootView: mainView)
            } else {
                window.rootViewController = UIHostingController(rootView: loginView)
            }
            
            self.window = window
            window.makeKeyAndVisible()
        }
    }
    
}

另外，這里是Info.plist檔案的截圖，專門擴展了相關區域：

uj5u.com熱心網友回復：

可StateObject從 SwiftUI 2.0 (iOS 14) 獲得，旨在在 View 中作業，而不是在類中作業（如SceneDelegate）

對于提供的場景，一種可能的解決方案是logicState僅將其用作頂層的屬性（在委托或主視圖中），但將其完全注入子視圖（而不僅僅是系結）并在內部觀察它。

所以它應該看起來像

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var loginStatus = UserLoginStatus() // << just hold here

// ...

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let mainView = MainView(loginStatus: loginStatus) // << here !!

和

struct MainView: View {
    @ObservedObject var loginStatus: UserLoginStatus   // << injected here

// ...
}

類似的可以在WeatherApp

uj5u.com熱心網友回復：

根據Apple 檔案，StateObject僅適用于 iOS 14 。

標籤：IOS 迅速 代码 迅捷

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