在iOS中查找rootViewController

Question

在 ShareKit 中，代码需要确定 rootViewController 的位置，以便它可以显示模式视图。由于某种原因，代码在 iOS 5 中失败：

    // Try to find the root view controller programmically

    // Find the top window (that is not an alert view or other window)
    UIWindow *topWindow = [[UIApplication sharedApplication] keyWindow];
    if (topWindow.windowLevel != UIWindowLevelNormal)
    {
        NSArray *windows = [[UIApplication sharedApplication] windows];
        for(topWindow in windows)
        {
            if (topWindow.windowLevel == UIWindowLevelNormal)
                break;
        }
    }

    UIView *rootView = [[topWindow subviews] objectAtIndex:0];  
    id nextResponder = [rootView nextResponder];

    if ([nextResponder isKindOfClass:[UIViewController class]])
        self.rootViewController = nextResponder;

    else
        NSAssert(NO, @"ShareKit: Could not find a root view controller.  You can assign one manually by calling [[SHK currentHelper] setRootViewController:YOURROOTVIEWCONTROLLER].");

这是命中断言。

简单地使用以下代码有什么问题吗？

rootViewController = [[[UIApplication sharedApplication] keyWindow] rootViewController];

这似乎运作良好。在某些条件下会失败吗？

Answer 1

我不确定您是否可以依赖 window.rootViewController b/c 您不必设置它。您只需向窗口添加一个子视图即可。以下似乎工作正常：

id rootVC = [[[[[UIApplication sharedApplication] keyWindow] subviews] objectAtIndex:0] nextResponder];

Answer 2

快速的方法，您可以从任何地方调用它：

/// EZSwiftExtensions - Gives you the VC on top so you can easily push your popups
public var topMostVC: UIViewController? {
    var presentedVC = UIApplication.sharedApplication().keyWindow?.rootViewController
    while let pVC = presentedVC?.presentedViewController {
        presentedVC = pVC
    }

    if presentedVC == nil {
        print("EZSwiftExtensions Error: You don't have any views set. You may be calling them in viewDidLoad. Try viewDidAppear instead.")
    }
    return presentedVC
}

它作为标准函数包含在：

https://github。 com/goktugyil/EZSwiftExtensions

Answer 3

这对我有用：

UIViewController * rootViewController = (UIViewController *)[[[UIApplication.sharedApplication.keyWindow subviews] firstObject];