xcode 如何消除“两级轮换”警告？

How to eliminate "two-stage rotation" warning?

提问by Matt.Z

My window's rootViewController is a UINavigationController Then.. In this navigation controller's rootViewController, I popup a modal view(a UITabBarController)

我的窗口的 rootViewController 是一个 UINavigationController 然后..在这个导航控制器的 rootViewController 中，我弹出一个模态视图（一个 UITabBarController）

something like this:

像这样：

UIWindow
->UINavigationController
-->MyFirstViewController<--In this class I run following code

[self.navigationController presentModalViewController:tabController animated:YES];

Then the debugger warning :Using two-stage rotation animation is not supported when rotating more than one view controller or view controllers not the window delegate

然后调试器警告：当旋转多个视图控制器或视图控制器不是窗口委托时，不支持使用两阶段旋转动画

However, if the modal view is not tabController this warning does not appear.

但是，如果模态视图不是 tabController，则不会出现此警告。

What will this behavior do harm to the application when I popup tabController modal view in a navigation controller?

当我在导航控制器中弹出 tabController 模态视图时，这种行为会对应用程序造成什么危害？

Or I should find another way to do this?

或者我应该找到另一种方法来做到这一点？

I found several similar questions on this site, but I don't get it...

我在这个网站上发现了几个类似的问题，但我不明白......

回答by LuckyLuke

The reason is that you are using a UITabBarController outside of the intended usage of it. It is ONLY intended to be used as a root controller, and should you need something similiar to a tabbar use toolbar. I was running into trouble with the exact problem about a half year ago. You will also run into other problems if you use it like that, unfortunately.

原因是您使用的 UITabBarController 超出了它的预期用途。它仅用作根控制器，如果您需要类似于标签栏使用工具栏的东西。大约半年前，我遇到了确切问题的麻烦。不幸的是，如果你这样使用它，你也会遇到其他问题。

UITabBarController documentation

UITabBarController 文档

Because the UITabBarController class inherits from the UIViewController class, tab bar controllers have their own view that is accessible through the view property. When deploying a tab bar interface, you must install this view as the root of your window. Unlike other view controllers, a tab bar interface should never be installed as a child of another view controller.

因为 UITabBarController 类继承自 UIViewController 类，所以标签栏控制器有自己的视图，可以通过 view 属性访问。部署标签栏界面时，必须将此视图安装为窗口的根目录。与其他视图控制器不同，标签栏界面不应作为另一个视图控制器的子项安装。

回答by Maciej Swic

This will also happen if you only add a blank UITabbarController without any child controllers, like so:

如果您只添加一个没有任何子控制器的空白 UITabbarController 也会发生这种情况，如下所示：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    //Tab bar controller
    UITabBarController* tabBarController = [[UITabBarController alloc] init];    
    [[self window] setRootViewController:tabBarController];

    [self.window makeKeyAndVisible];
    return YES;
}

The warning will go away if you add a child view controller to the UITabBarController before declaring it the rootViewController of your UIWindow.

如果在将子视图控制器声明为 UIWindow 的 rootViewController 之前将子视图控制器添加到 UITabBarController，警告将消失。

回答by Oliver

I got the same warning when subclassing UITabBarController but forgetting to call the base class's viewWillAppear: method in my own class.

我在继承 UITabBarController 时收到了同样的警告，但忘记在我自己的类中调用基类的 viewWillAppear: 方法。

- (void) viewWillAppear:(BOOL)animated {

  [super viewWillAppear:animated]    // <--- adding this fixed the warning

  ...

}

回答by Klaus Thul

I have an app where a UITabBarControlleris the root view controller. Depending on an in-app purchase, the child view controllers are different.

我有一个应用程序，其中 aUITabBarController是根视图控制器。根据应用内购买，子视图控制器是不同的。

In my NIB, I had the UITabBarControllerwithout any child view controllers. I added the child view controllers in application:didFinishLaunchingWithOptions:

在我的 NIB 中，我UITabBarController没有任何子视图控制器。我添加了子视图控制器application:didFinishLaunchingWithOptions:

This caused the warning "two-stage" rotation to appear. As soon as I added one single child view controller to the tabbar controller in the NIB it disappeared.

这导致出现警告“两阶段”轮换。一旦我向 NIB 中的选项卡栏控制器添加了一个子视图控制器，它就消失了。

回答by Diogo Hacka

@Maciej Swic's answer helped me a bit.

@Maciej Swic 的回答对我有所帮助。

In my case I had already 2 child for the UITabBarController.

就我而言，我已经为 UITabBarController 生了 2 个孩子。

For some strange reason all I need was to put

出于某种奇怪的原因，我所需要的只是把

[self.window makeKeyAndVisible];

[self.window makeKeyAndVisible];

after I added the 2 children.

在我添加了 2 个孩子之后。

回答by dave adelson

Oliver's answer did the trick for me...it was interesting, though...i had not been having any problems until i added a viewWillAppear:animated method to to the subclassed tabviewcontroller...at that point, everything went haywire, until it was fixed by adding the [super viewWillAppear:animated] statement Oliver suggests...

Oliver 的回答对我有用……虽然很有趣……我一直没有遇到任何问题，直到我向子类 tabviewcontroller 添加了一个 viewWillAppear:animated 方法……那时，一切都变得混乱，直到它是通过添加 [super viewWillAppear:animated] 语句修复的，奥利弗建议......

回答by bollhav

Had problem with Two-stage animation warning with the following order:

出现以下顺序的两阶段动画警告问题：

self.window.rootViewController = self.tabBarController;
self.tabBarController.selectedIndex = 0;

But changing the order help me to eliminate the warning.

但是更改顺序可以帮助我消除警告。

self.tabBarController.selectedIndex = 0;
self.window.rootViewController = self.tabBarController;

Hope this helps.

希望这可以帮助。