刚开始使用Xcode 4.5，我在控制台得到了这个错误:
警告:试图在< ViewController: 0x1ec3e000>上显示< finishViewController: 0x1e56e0a0 >，其视图不在窗口层次结构中!
视图仍在显示，应用程序中的一切都在正常工作。这是iOS 6的新功能吗?
这是我用来在视图之间更改的代码:
UIStoryboard *storyboard = self.storyboard;
finishViewController *finished =
[storyboard instantiateViewControllerWithIdentifier:@"finishViewController"];
[self presentViewController:finished animated:NO completion:NULL];
当前回答
如果其他解决方案因为某些原因看起来不太好，你仍然可以使用这个不错的老方法，用延迟0表示，就像这样:
dispatch_after(0, dispatch_get_main_queue(), ^{
finishViewController *finished = [self.storyboard instantiateViewControllerWithIdentifier:@"finishViewController"];
[self presentViewController:finished animated:NO completion:NULL];
});
虽然我没有看到任何文件保证你的VC会在调度块计划执行的时间上处于视图层次结构上，但我观察到它会工作得很好。
使用延迟，例如0.2秒也是一种选择。最好的事情-这样你就不需要在viewDidAppear中混乱布尔变量:
其他回答
当我试图在viewDidLoad中呈现一个UIViewController时，我也遇到了这个问题。James Bedford的答案是可行的，但我的应用程序先显示了1到2秒的背景。
经过一些研究，我找到了一种方法来解决这个使用addChildViewController。
- (void)viewDidLoad
{
...
[self.view addSubview: navigationViewController.view];
[self addChildViewController: navigationViewController];
...
}
我在Swift 4.2上也有类似的问题，但我的观点没有从视图周期中呈现出来。我发现我有多个segue要同时呈现。所以我使用dispatchAsyncAfter。
func updateView() {
DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) { [weak self] in
// for programmatically presenting view controller
// present(viewController, animated: true, completion: nil)
//For Story board segue. you will also have to setup prepare segue for this to work.
self?.performSegue(withIdentifier: "Identifier", sender: nil)
}
}
In case it helps anyone, my issue was extremely silly. Totally my fault of course. A notification was triggering a method that was calling the modal. But I wasn't removing the notification correctly, so at some point, I would have more than one notification, so the modal would get called multiple times. Of course, after you call the modal once, the viewcontroller that calls it it's not longer in the view hierarchy, that's why we see this issue. My situation caused a bunch of other issue too, as you would expect.
总之，无论你做什么，都要确保模态不会被调用超过一次。
viewWillLayoutSubviews和viewDidLayoutSubviews (iOS 5.0+)可以用于此目的。它们在viewDidAppear之前被调用。
要将任何子视图显示到主视图，请使用以下代码
UIViewController *yourCurrentViewController = [UIApplication sharedApplication].keyWindow.rootViewController;
while (yourCurrentViewController.presentedViewController)
{
yourCurrentViewController = yourCurrentViewController.presentedViewController;
}
[yourCurrentViewController presentViewController:composeViewController animated:YES completion:nil];
对于从主视图中解散任何子视图，请使用以下代码
UIViewController *yourCurrentViewController = [UIApplication sharedApplication].keyWindow.rootViewController;
while (yourCurrentViewController.presentedViewController)
{
yourCurrentViewController = yourCurrentViewController.presentedViewController;
}
[yourCurrentViewController dismissViewControllerAnimated:YES completion:nil];
