iOS 移除 SceneDelegate

xcode11创建项目新增SceneDelegate文件，AppDelegate文件结构也发生变化，在AppDelegate.h文件中没有了window属性，而是在SceneDelegate.h中，可见AppDelegate不管理window而是交给SceneDelegate。由于这些是ios13新增，所以SceneDelegate在ios13以下的系统是不支持。

那么如果我的App不需要支持多个Scene ，或者需要兼容 iOS13.0以下的版本怎么办呢，其实很简单，移除掉 SceneDelegate 即可。

1、工程中删除 SceneDelegate 文件

2、和往常一样在 AppDelegate 中添加 window 属性

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
}

3、移除 AppDelegate 中多余的 UIScene 代理方法

移除前

import UIKit

@main
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
}

// MARK: UISceneSession Lifecycle

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.
}

}

移除后

import UIKit

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.

    return true
}

}

4、最后在info.plist文件中移除Application Scene Manifest

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