从另一个模态视图创建模态视图失败

Question

在以模态方式创建的视图中，按下按钮会导致取消模态视图并加载另一个模态视图。

- (void)loadLanguageSelectionView {
    [self dismissViewControllerAnimated:YES completion:nil];
    UIViewController *languageSelectionController = [[LanguageSelectionViewController alloc] initWithNibName:nil bundle:nil];
    [languageSelectionController setModalPresentationStyle:UIModalPresentationCustom];
    [languageSelectionController setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
    [self presentViewController:languageSelectionController animated:YES completion:nil];
}

执行此代码块时会引发以下错误：

DenkoStation[4259:73173] Warning: Attempt to present <LanguageSelectionViewController: 0x7b185430> on <ViewController: 0x79f52e50> whose view is not in the window hierarchy!

让我感到惊讶的是，在我对代码as outlined here进行一些更改之前，代码运行得很愉快。

哪里出错？

Answer 1

因为你试图在viewController之上呈现一个viewController，它已被解除并且不再在窗口层次结构中。

你可以尝试的是，你可以从当前的viewController中获取ParentViewController引用然后你可以在ParentViewController上呈现新的viewController像这样：

- (void)loadLanguageSelectionView {
    UIViewController *parentController = self.presentingViewController;
    [self dismissViewControllerAnimated:YES completion:^{
        UIViewController *languageSelectionController = [[LanguageSelectionViewController alloc] initWithNibName:nil bundle:nil];
        [languageSelectionController setModalPresentationStyle:UIModalPresentationCustom];
        [languageSelectionController setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
        [parentController presentViewController:languageSelectionController animated:YES completion:nil];
    }];
}