有没有办法在呈现另一个ViewController之后将其关闭？

Question

After some time searching for an answer, I have to admit that i'm pretty confuse with this case.

At my job, I'm asked to do something really specific :

I have to present a UIViewController on a previous UIViewController, actually, the current ViewController dismiss itself before the second appear. That give the whole thing a funny animation that a ViewController goes down and another rise from the bottom after this. But... It's not really "pro" and, we're able to see the rootViewController behind the scene during the animation.

So, I have to precise that there is NO NavigationController, that would have made this a lot easier in my opinion, so I'm forced to do it with two UIViewController, and there is my actual code :

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Storyboard" bundle:nil];
        UIViewController *controller = [storyboard instantiateViewControllerWithIdentifier:@"userViewController"];
        [[UIApplication sharedApplication].keyWindow.rootViewController presentViewController:controller animated:YES completion:^{
            [self dismissViewControllerAnimated:YES completion:nil];
}];     

It is call right after a button is pressed, so there is no problem with the actual ViewController viewDidLoad or viewDidAppear I think.

But each time this code runs, I get the following error :

[1163:17641] Warning: Attempt to present <UserViewController: 0x7b0f0a00> on <EIHomeViewController: 0x7b0d2a00> whose view is not in the window hierarchy!

I don't really know how I could manage to keep a trace of the current UIViewController to dismiss it in the next ViewController viewDidAppear to be sure there will be no "blackout" on the screen.

Thank you for your help in advance!

Answer 1

Try this code:

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Storyboard" bundle:nil];
UIViewController *controller = [storyboard instantiateViewControllerWithIdentifier:@"userViewController"];
[self dismissViewControllerAnimated:NO completion:^{
    [[UIApplication sharedApplication].keyWindow.rootViewController presentViewController:controller animated:NO completion:nil];
}];