Use of scene delegate for apps that does not support multiple windows

Question

I know that scene delegate can only be used on iOS 13 and later. For my app to support iOS 12 and earlier versions, its either I opt-out of scene delegate or set @available tag to remind Xcode. I read about the use of scene delegate here. Based on what I see, aside from supporting multiple windows, I am not aware of any other advantage of using scene delegate on apps that DOES NOT support multiple windows. Will there be a boost in performance? So, can I just use App Delegate alone if my app does not plan on supporting multiple windows in the future?

Answer 1

windows are managed by WindowScene ,

you need register your new window ( multiple windows ) to WindowScene , with SceneDelegate

     YourWindow  * window = [[YourWindow alloc] initWithFrame:CGRectMake(0, 0, windowWidth, windowWidth)];
window.hidden = false

    // there is a time delay,
    // if activationState = UISceneActivationStateUnattached

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
             if (@available(iOS 13.0, *)) {
                 for (UIWindowScene *windowScene in [UIApplication sharedApplication].connectedScenes) {
                     if (windowScene.activationState == UISceneActivationStateForegroundActive) {
                        window.windowScene = windowScene ;
                        break;
                   }
                         
              }
         }
     });