popoverPresentationController在iphone上不能实现浮窗效果的问题

大家好,参考这帖子 http://www.jianshu.com/p/8740a7ddc99d 我写了个demon,它说如果下面这个函数返回的是none,就可以出浮窗

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

我试了,但是不能出浮窗效果,总是从下往上弹起的全屏效果,请问为啥呢?
下面是我的代码,我都老老实实设置的属性

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

@IBAction func clickBtn(_ sender: AnyObject) {
    let pop = PopViewController()
    pop.modalPresentationStyle = .popover
    pop.popoverPresentationController?.delegate = self

    pop.popoverPresentationController?.sourceView = btn
    pop.preferredContentSize = CGSize(width:100, height:100)

    pop.popoverPresentationController?.sourceRect = btn.frame
    pop.popoverPresentationController?.permittedArrowDirections = .down



    self.present(pop, animated: true, completion: nil)
}

http://blog.csdn.net/chun799/article/details/6988359

发现是UIPopoverPresentationControllerDelegate的代理方法没有被执行，具体啥原因我也不知道，我也遇到这种问题，楼主解决了吗？