Ios 如果应用程序委派要使用主情节提要文件，则必须实现window属性

我已经尝试了在stackoverflow中找到的所有解决方案，但都不起作用

这是我当前的AppDelegate.swift文件，我想我正在以某种方式实现窗口属性：

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    window = UIWindow()
    window?.makeKeyAndVisible()
    let mainVC = UIViewController()
    window?.rootViewController = mainVC

    return true
}

// 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.
    window = UIWindow()
          window?.makeKeyAndVisible()
          let mainVC = UIViewController()
          window?.rootViewController = mainVC
    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.
    window = UIWindow()
          window?.makeKeyAndVisible()
          let mainVC = UIViewController()
          window?.rootViewController = mainVC
}

导入UIKit
@UIApplicationMain
类AppDelegate:UIResponder、UIApplicationLegate{
变量窗口：UIWindow？
func应用程序（application:UIApplication，didFinishLaunchingWithOptions launchOptions:[UIApplication.launchOptions键：任意]？）->Bool{
//应用程序启动后自定义的覆盖点。
window=ui窗口（）
窗口？.makeKeyAndVisible（）
让mainVC=UIViewController（）
窗口？.rootViewController=mainVC
返回真值
}
//MARK:UISceneSession生命周期
@可用（iOS 13.0，*）
func应用程序（uApplication:UIApplication，用于连接的配置SceneSession:UISceneSession，选项：UIScene.ConnectionOptions）->UISceneConfiguration{
//在创建新场景会话时调用。
//使用此方法可以选择配置以创建新场景。
window=UIWindow（）
窗口？.makeKeyAndVisible（）
让mainVC=UIViewController（）
窗口？.rootViewController=mainVC
返回UISceneConfiguration（名称：“默认配置”，会话角色：ConnectionSceneSession.role）
}
@可用（iOS 13.0，*）
func应用程序（application:UIApplication，didDiscardSceneSessions sceneSessions:Set）{
//当用户放弃场景会话时调用。
//如果在应用程序未运行时丢弃了任何会话，则将在application:didFinishLaunchingWithOptions后不久调用该会话。
//使用此方法释放特定于被丢弃场景的任何资源，因为它们不会返回。
window=UIWindow（）
窗口？.makeKeyAndVisible（）
让mainVC=UIViewController（）
窗口？.rootViewController=mainVC
}

}

---

会发生什么情况，使警告仍然出现，而我的应用程序继续显示黑色屏幕？

我会一步一步地指导您

首先从项目中删除SceneDelegate文件

将变量窗口：UIWindow？添加到AppDelegate

从AppDelegate中删除下面的func

//MARK:UISceneSession生命周期

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)
}

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.
}

---

如果您正在开发Objective C应用程序，并且遇到此错误，请按照上面提到的相同步骤进行操作，只需在步骤1中进行更改。

---

添加@property（非原子，保留）窗口；要AppDelegate.h

在Xcode 11.4及更高版本中创建新项目，请使用SceneDelegate文件创建项目目录结构

如果你试图运行一个项目，你会得到一个错误

步骤1：删除SceneDelegate.h和SceneDelegate.m

步骤2：在AppDelegate.h中创建窗口属性

@property (strong, nonatomic) UIWindow *window;

步骤3：在主情节提要中，为ViewController设置情节提要id

并在appdelegate的didFinishLaunchingWithOptions方法中添加一个设置窗口

UIStoryboard *sb = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
UIViewController *vc = [sb instantiateViewControllerWithIdentifier:@"ViewController"];
vc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.rootViewController = vc;
[self.window makeKeyAndVisible];

return YES;

对于Swift：使用以下代码

@UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?

func application(_ application: UIApplication, 
didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: 
  Any]?) -> Bool {
    // Override point for customization after application launch.
    return true
}

}

注意：不要在didFinishLaunchingWithOptions方法中为swift添加窗口。

---

我刚刚在AppDelegate类中添加了

var window:UIWindow？

，问题得到了解决。

完成了所有指示，但不起作用，如果我没有弄错的话，我已经尝试过了，无论如何感谢您的帮助。我认为您没有在故事板中设置入口点。如果未设置，则更新func，如下面的代码所示。func应用程序（application:UIApplication，didFinishLaunchWithOptions launchOptions:[UIApplication.launchOptions Key:Any]？）->Bool{let navigation=UINavigationController（rootViewController:ViewController（））let frame=UIScreen.main.bounds window=UIWindow（frame:frame）window！.rootViewController=navigation window！.makeKeyAndVisible（）return true}仍然一样，这真是一个让人头疼的问题，无论如何，谢谢你的帮助。我也为swift添加了答案。请检查以上，谢谢，但我使用的是Swift。答案非常适合Swift。与目标C相同的步骤，添加@property（非原子，保留）IBOutlet UIWindow；到AppDelegate.h

@UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?

func application(_ application: UIApplication, 
didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: 
  Any]?) -> Bool {
    // Override point for customization after application launch.
    return true
}