SwiftUI下如何为iPad锁定屏幕方向？

核心原因 #

iPad默认采用多场景（Scene）架构，仅通过AppDelegate的方向控制方法无法覆盖所有场景，需要结合UIWindowSceneDelegate来实现精细化的方向管控。

具体解决步骤 #

1. 实现SceneDelegate类

创建专门的SceneDelegate来处理场景级别的方向限制：

class SceneDelegate: NSObject, UIWindowSceneDelegate {
    static var orientationLock: UIInterfaceOrientationMask = .all
    
    func windowScene(_ windowScene: UIWindowScene, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {
        return SceneDelegate.orientationLock
    }
}

2. 关联SceneDelegate到项目

在Xcode的Info.plist中，找到Application Scene Manifest -> Scene Configuration -> Application Session Role -> Item 0，将Scene Delegate Class的值设置为$(PRODUCT_MODULE_NAME).SceneDelegate，确保SwiftUI能正确识别该代理类。

同时保留原有AppDelegate以兼容iPhone场景：

@main
struct MainApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

class AppDelegate: NSObject, UIApplicationDelegate {
    func application(_ application: UIApplication, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {
        return SceneDelegate.orientationLock
    }
}

3. 修正视图中的方向切换逻辑

iOS 13+ 中UIDevice.setValue(_:forKey:)在iPad上失效，改用UIWindowScene的官方API强制切换方向：

struct ContentView : View {
    var body : some View {
        ZStack {
            Text("Hello World!")
                .onAppear {
                    SceneDelegate.orientationLock = .portrait
                    forceOrientation(to: .portrait)
                }
                .onDisappear {
                    SceneDelegate.orientationLock = .portrait
                    forceOrientation(to: .portrait)
                }
        }
    }
    
    private func forceOrientation(to orientation: UIInterfaceOrientation) {
        guard let windowScene = UIApplication.shared.connectedScenes.first as? UIWindowScene else { return }
        windowScene.requestGeometryUpdate(.iOS(interfaceOrientations: orientation.mask))
    }
}

extension UIInterfaceOrientation {
    var mask: UIInterfaceOrientationMask {
        switch self {
        case .portrait: return .portrait
        case .portraitUpsideDown: return .portraitUpsideDown
        case .landscapeLeft: return .landscapeLeft
        case .landscapeRight: return .landscapeRight
        default: return .all
        }
    }
}

4. 检查Target配置

在Xcode的Target -> Deployment Info中，勾选iPad的所有方向选项（竖屏、倒竖屏、左横屏、右横屏），确保代码具备动态切换方向的基础权限。

内容的提问来源于stack exchange，提问作者TrappinNachos