因为需要对低版本的兼容，所以不能直接使用新的api ，SceneDelegate 这个就需要删掉了
主要是因为info.plist文件中有对 SceneDelegate的设置
Screen Shot 2021-05-25 at 4.07.47 PM.png
看到这里有种冲动项改掉 delegate Class Name 为AppDelegate ，我改了，崩掉了
Info.plist configuration "Default Configuration" for UIWindowSceneSessionRoleApplication contained UISceneDelegateClassName, "AppDelegate", but it does not conform to the UISceneDelegate protocol.
就是说 UISceneDelegate 这个AppDelegate没有实现 UISceneDelegate 方法,如果你把方法移动到AppDelegate中也是可以的，并把UISceneDelegate的< UIWindowSceneDelegate> 放到AppDelegate,方法移到AppDelegate, 以及window添加，就相当于（UISceneDelegate 有的，移到AppDelegate， + info.plist配置修改）也是可以的，直接运行成功
如果不需要这么麻烦，只是为了兼容低版本，直接删掉不需要的就好了，没必要多次一举，以下几个步骤
1、然后这个 Application Scene Manifest 这一栏 删掉了就好了，可以运行不再崩溃
2、SceneDelegate.h和SceneDelegate.m我们也不会用上了，删掉
3、也因为AppDelegate中的两个方法 也是需要 13.0版本的，所以也需要删掉，接下来就差不多可以自由发挥了
- (UISceneConfiguration *)application:(UIApplication *)application configurationForConnectingSceneSession:(UISceneSession *)connectingSceneSession options:(UISceneConnectionOptions *)options {
// Called when a new scene session is being created.
// Use this method to select a configuration to create the new scene with.
return [[UISceneConfiguration alloc] initWithName:@"Default Configuration" sessionRole:connectingSceneSession.role];
}
- (void)application:(UIApplication *)application didDiscardSceneSessions:(NSSet<UISceneSession *> *)sceneSessions {
// 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.
}
4、然后在AppDelegate.h中添加window属性
Screen Shot 2021-05-25 at 4.23.42 PM.png
