Attempt to present ViewController whose view is not in the windows hierarchy

Question

I meet a strange problem: I made 2 view controllers for wich I can switch the view with code:

var currentViewController:UIViewController=UIApplication.shared         


        

Answer 1

Xcode error significance for roughly: this view is not in the Window of the view hierarchy.

What I don't think the above answer questions, but maybe you might have wondered why this would happen.

But I find that you are the reasons for this problem is likely to be in the ViewController life cycle at ViewDidLoading switch view Code execution inside.

Reason is probably that, when the ViewController implementation allco init during initialization, it will be executed asynchronously viewWillLoad - > viewDidLoad... -- -- -- -- > viewDidApper. Then may be in code execution to the viewDidLoad. The ViewController may not assign values to the Window. The rootViewController. So we directly use [self presentViewController:] will appear this error.

It is recommended that you move the code of the switch to ViewDidApper.

I hope it will help you.