UIWindow setRootViewController不清除现有层次结构 [英] UIWindow setRootViewController not clearing existing hierarchy

问题描述

在我的应用中，我根据用户操作(例如，登录/注销功能.

In my app I programmatically change root view controllers based on user actions e.g. login/logout functionality.

在iOS 8中-我注意到一个奇怪的问题.即使在窗口上设置了rootViewController之后，旧的层次结构仍然存在.我只是通过捕获视图层次结构对其进行了验证.

In iOS 8 - I'm noticing a strange issue. Even after setting rootViewController on the window, the old hierarchy still persists. I just verified it by capturing view hierarchy.

- (void) logout{
     [self.window setRootViewController:[self loadLoginView]];
}

-(UIViewController *) loadLoginView{
      WelcomeScreenVC *wsVC;
      wsVC = [[WelcomeScreenVC alloc] initWithNibName:@"WelcomeScreenVC" bundle:nil];
      UINavigationController *onboardingVC = [[UINavigationController alloc]initWithRootViewController:wsVC];
      return onboardingVC;
 }

即使执行了这一行代码之后，旧的登录视图层次结构仍然存在.如果有人可以建议幕后发生的事情，我们将不胜感激.

Even after executing this line of code, the old logged in view hierarchy still persists. Would appreciate if anybody can suggest what's happening behind the scenes.

我只是看了UIWindow setRootViewController文档，这是苹果公司要说的:

I just looked at UIWindow setRootViewController documentation and here's what Apple has to say about it:

根视图控制器提供窗口的内容视图. 将视图控制器分配给该属性(以编程方式 或使用Interface Builder)将视图控制器的视图安装为 窗口的内容视图.如果窗口已有视图 层次结构，旧视图在新视图之前被删除 已安装.

The root view controller provides the content view of the window. Assigning a view controller to this property (either programmatically or using Interface Builder) installs the view controller’s view as the content view of the window. If the window has an existing view hierarchy, the old views are removed before the new ones are installed.

推荐答案

我注意到了同样的事情.

I have noticed the very same thing.

基本上，我有一个相当复杂的情节提要，可以用作登录/欢迎界面.该界面位于导航控制器中，该控制器以模态形式显示另一个导航控制器.

Basically, I have a fairly complicated storyboard that acts as a login/welcome interface. This interface sits in a navigation controller, which presents another navigation controller modally.

在特定点之后，用户执行将其转换到主界面的操作.使用iOS 8视图调试器，我注意到在设置窗口的rootViewController属性后，旧的视图层次结构仍然存在.

After a certain point, the user takes an action that transitions him to the main interface. Using the iOS 8 view debugger I noticed that the old view hierarchy was still around after setting the rootViewController property of the window.

我的解决方案，现在是在重新确定window.rootViewController属性之前使用以下代码:

My solution, for now is to use the following code, right before I re-assing the window.rootViewController property:

for (UIView* subView in self.window.rootViewController.view.subviews) {
    [subView removeFromSuperview];
}
[self.window.rootViewController.view removeFromSuperview];

它不是很漂亮，但是可以用.

It ain't pretty, but it works.

我注意到的另一件奇怪的事情是，使用此方法未正确清理Welcome接口以模态形式显示的viewController.我必须手动将其关闭并进行清理.

Another odd thing I noticed is that the welcome interface's modally presented viewController is not properly cleaned up using this method. I have to manually dismiss it AND do this clean up.

这篇关于UIWindow setRootViewController不清除现有层次结构的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！