Warning: Attempt to present <UINavigationController: 0x6e8ade0> on <LoginViewController: 0x6b3ef90> whose view is not in the window hierarchy

错误提示：iOS 7.1环境下测试没问题，换到ios8环境下回报这个错误Warning: Attempt to present <UINavigationController: 0x6e8ade0> on <LoginViewController: 0x6b3ef90> whose view is not in the window hierarchy!

1. 代码逻辑是：

LoginViewController在登陆后会present到一个UINavigationController，在这个UINavigationController中，会有监听事件，监听到后会present到另外一个新的UINavigationController，这个错误就是跳转的时候引发的，我用的-(UIViewController *)getCurrentRootViewController这个函数来获取当前顶层的控制器，但是到ios8环境下，这个检测不到LoginViewController之后所有得viewcontroller，好像只能显示window的rootviewcontroller请问怎么解决

//获取当前viewcontroller
-(UIViewController *)getCurrentRootViewController {
    UIViewController *result;
    // 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]])
        result = nextResponder;
    else if ([topWindow respondsToSelector:@selector(rootViewController)] && topWindow.rootViewController != nil)
        result = topWindow.rootViewController;
    else
        NSAssert(NO, @"ShareKit: Could not find a root view controller.  You can assign one manually by calling [[SHK currentHelper] setRootViewController:YOURROOTVIEWCONTROLLER].");
    return result;
}

1.解决方法：

看了一下你的代码，你不应该用 [self getCurrentRootViewController] 去present ，
因为当第一次present之后，此时window上面的顶级视图是 ffViewController ，这时候如果你继续present 需要 用 ffViewController 这个对象。

我大概理解你的想法是 想当前的controller 直接 模态
通过我下面的函数可以获取当前的controller  （    [[self topViewController] presentViewController:[[UIViewController alloc] init] animated:YES completion:nil];）
- (UIViewController*)topViewController
{
    return [self topViewControllerWithRootViewController:self.window.rootViewController];
}

- (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController
{
    if ([rootViewController isKindOfClass:[UITabBarController class]]) {
        UITabBarController *tabBarController = (UITabBarController *)rootViewController;
        return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
    } else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
        UINavigationController* navigationController = (UINavigationController*)rootViewController;
        return [self topViewControllerWithRootViewController:navigationController.visibleViewController];
    } else if (rootViewController.presentedViewController) {
        UIViewController* presentedViewController = rootViewController.presentedViewController;
        return [self topViewControllerWithRootViewController:presentedViewController];
    } else {
        return rootViewController;
    }
}

参考：http://www.cocoachina.com/bbs/read.php?tid=295517