使用 UISceneDelegate 将旧 Xcode 项目迁移到新项目

Question

我有一个没有 UISceneDelegate 方法的旧 Xcode 项目。是否可以使用 UISceneDelegate 方法将旧 Xcode 项目迁移到新项目，但仍保持与 iOS 12 的兼容性？

如果是这样，怎么做？因为我在 iOS 14 中看到了很多错误，唯一的解决方法是使用 UISceneDelegate 方法。

Answer 1

编辑 1：

确保在 View Controller 的视图呈现后查询 windowOrientation。通常在viewDidLoad() 和viewWillAppear(_:) 中，view.window 是nil，请检查此answer。只需检查 viewDidAppear(_:) 中 windowOrientation 的值即可。

如果您在尝试以下定义之前访问此值时遇到问题

private var windowOrientation: UIInterfaceOrientation {
    if #available(iOS 13.0, *) {
        return UIApplication.shared.windows.first?.windowScene?.interfaceOrientation ?? .unknown
    } else {
        // Fallback on earlier versions
        return UIApplication.shared.statusBarOrientation
    }
}

我不确定您的应用是否使用多个窗口，但如果只有一个（因为您没有以编程方式创建任何窗口），以下定义应该可以正常工作。

var hasTopNotch: Bool {
    return UIApplication.shared.windows.first?.safeAreaInsets.top ?? 0 > 20
}

原答案：

UISceneDelegate已经在iOS 13.0中引入，所以无法兼容iOS 12，需要完全依赖UIApplicationDelegate。要支持UISceneDelegate 中的iOS 13.x，您需要添加显式可用性检查以避免编译错误。

步骤 1：在Info.plist 中添加场景清单

打开Info.plist为Source Code并添加以下内容

<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>$(PRODUCT_MODULE_NAME).SceneDelegate</string>
                <key>UISceneStoryboardFile</key>
                <string>Main</string>
            </dict>
        </array>
    </dict>
</dict>

第二步：创建SceneDelegate.swift文件，内容如下

import UIKit
@available(iOS 13.0, *)
class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).
        guard let _ = (scene as? UIWindowScene) else { return }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
        // This occurs shortly after the scene enters the background, or when its session is discarded.
        // Release any resources associated with this scene that can be re-created the next time the scene connects.
        // The scene may re-connect later, as its session was not neccessarily discarded (see `application:didDiscardSceneSessions` instead).
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Called when the scene has moved from an inactive state to an active state.
        // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Called when the scene will move from an active state to an inactive state.
        // This may occur due to temporary interruptions (ex. an incoming phone call).
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Called as the scene transitions from the background to the foreground.
        // Use this method to undo the changes made on entering the background.
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Called as the scene transitions from the foreground to the background.
        // Use this method to save data, release shared resources, and store enough scene-specific state information
        // to restore the scene back to its current state.
    }


}

第三步：更新AppDelegate

1. 添加 UISceneSession Lifecycle 方法。

// MARK: UISceneSession Lifecycle
@available(iOS 13.0, *)
func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
    // Called when a new scene session is being created.
    // Use this method to select a configuration to create the new scene with.
    return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
}
@available(iOS 13.0, *)
func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
    // Called when the user discards a scene session.
    // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
    // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
}

ii) 最后参考Apple Documentation。您可以参考https://dev.to/kevinmaarek/add-a-scene-delegate-to-your-current-project-5on 了解更多清理和设置任务。