ios - 如何呈现 TabBarController 模态

Question

从一个 View ( LoginTesteInicial ) 我可以转到两个 tabBarControllers，但是当我运行代码时，它崩溃并出现以下错误: Attempt to present <UITabBarController: 0x8a4a870> on <LoginTesteInicial: 0x8a46970> whose view is not in the window hierarchy!

这是我来自 LoginTesteInicial.m 的代码:

UITabBarController *vc;

if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {

    vc = [[UIStoryboard storyboardWithName:@"Main_iPad" bundle:nil] instantiateViewControllerWithIdentifier:@"TabBarSemLogin"];
} else {

    vc = [[UIStoryboard storyboardWithName:@"Main_iPhone" bundle:nil] instantiateViewControllerWithIdentifier:@"TabBarSemLogin"];
}

[vc setModalTransitionStyle:UIModalTransitionStyleFlipHorizontal];

[self presentViewController:vc animated:YES completion:nil];

Answer 1

您的问题的答案是，当调用 -viewDidLoad 时， View Controller 的 View 不在 View 层次结构中。您需要等到 View 被放入 View 层次结构中。这可以在 -viewWillAppear: 或 -viewDidAppear: 中完成。

---

您收到的“对开始/结束外观转换的调用不平衡”警告是因为 View Controller 在被另一个 View Controller 替换之前尚未完全加载。为避免该警告，您可以使用 -performSelector:withObject:afterDelay: 在下一个运行循环中安排当前 View Controller 。

- (void)viewDidAppear:(BOOL)animated
{
    …
    [self performSelector:@selector(showTabBarController) withObject:nil afterDelay:0.0];
}

- (void)showTabBarController
{
    UITabBarController *vc;
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        vc = [[UIStoryboard storyboardWithName:@"Main_iPad" bundle:nil] instantiateViewControllerWithIdentifier:@"TabBarSemLogin"];
    } else {
        vc = [[UIStoryboard storyboardWithName:@"Main_iPhone" bundle:nil] instantiateViewControllerWithIdentifier:@"TabBarSemLogin"];
    }

    [vc setModalTransitionStyle:UIModalTransitionStyleFlipHorizontal];
    [self presentViewController:vc animated:YES completion:nil];
}