ios - 在一个函数中以编程方式在彼此之上呈现两个 UIViewController

Question

我正在尝试呈现 (1) ScrollViewController，然后在呈现之后呈现 (2) ImagePicker。但是，仅显示 ScrollViewController，之后不显示 ImagePicker。

就个人而言，下面的代码工作正常，只是当一个跟随另一个时，它不起作用。我试过在完成处理程序中包含一个，仍然没有成功。

没有错误显示，除了，当序列发生时，Xcode 调试区域显示但完全空白，没有错误消息或警告。

问题:

What exactly is going on here that I'm missing? Why aren't both being presented? How can I ensure both the ScrollViewController and ImagePicker are displayed, one after the other?

(1) ScrollView Controller :

 let storyboard = UIStoryboard(name: "Main", bundle: nil)
 let vc = storyboard.instantiateViewControllerWithIdentifier("ScrollViewControllerID") as! ScrollViewController
 self.presentViewController(vc, animated: true, completion: nil)

(2) 图片选择器:

 let imagePicker = MyImagePickerController()
 imagePicker.delegate = self
 imagePicker.sourceType = .PhotoLibrary
 imagePicker.allowsEditing = false
 imagePicker.modalTransitionStyle = UIModalTransitionStyle.CoverVertical
 self.presentViewController(imagePicker, animated: true, completion: nil)

Answer 1

View Controller 一次只能呈现一个呈现的 Controller 。事实上，有一个属性:presentedViewController: UIViewController? 暗示了这一点。协调这些行动:

一个。仅展示您的基本 VC 中的第一个 VC。

B.在第一个演示调用的完成处理程序中，让第二个 VC 显示最上面的最后一个:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("ScrollViewControllerID") as! ScrollViewController
self.presentViewController(vc, animated: true) {
    let imagePicker = MyImagePickerController()
    imagePicker.delegate = self
    imagePicker.sourceType = .PhotoLibrary
    imagePicker.allowsEditing = false
    imagePicker.modalTransitionStyle = UIModalTransitionStyle.CoverVertical
    vc.presentViewController(imagePicker, animated: true, completion: nil)
}