如果宽度<30

Question

这是主控制器，它是一个简单的故事板弹出窗口。问题是如果我将宽度设置为低于50，则会出现奇怪的阴影。 https://www.dropbox.com/s/bboh6cxnrge6q9g/Screen%20Shot%202015-09-04%20at%202.20.03%20PM.png?dl=0

https://www.dropbox.com/s/lrw3ec44m0997q4/Screen%20Shot%202015-09-04%20at%202.20.56%20PM.png?dl=0

class MainViewController: UIViewController, UIPopoverPresentationControllerDelegate
{
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.

}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
{
if let popupView = segue.destinationViewController as? UIViewController
{
  if let popup = popupView.popoverPresentationController
  {
    popup.delegate = self
           popupView.preferredContentSize = CGSize(width: 30, height: 250)
          }
}
    }

func adaptivePresentationStyleForPresentationController(controller:      UIPresentationController) -> UIModalPresentationStyle
{
return UIModalPresentationStyle.None
}

}