UIAlertController和UIViewAlertForUnsatisfiableConstraints错误

Question

我昨天升级到Xcode 10.2，并开始使用Swift 5，当出现我的UIAlertController照片提示时，注意到此错误。我不记得在Xcode 10.1中看到过它

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x600001321e00 UIView:0x7fe1246070a0.width == - 16   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.

我读了这个问题How to trap on UIViewAlertForUnsatisfiableConstraints? 并能够将错误定位到我的UIAlertController（以红色突出显示）

这是我的代码：

 @objc private func promptPhoto() {

    let prompt = UIAlertController(title: "Choose a Photo",
                                   message: "",
                                   preferredStyle: .actionSheet)

    let imagePicker = UIImagePickerController()
    imagePicker.delegate = self

    let camerAction = UIAlertAction(title: "Camera", style: .default) { _ in
      guard self.isCameraAccessible() else {
        self.showAlert(title: "Oops", message: "Camera is not available")
        return
      }
      imagePicker.sourceType = .camera
      imagePicker.allowsEditing = true
      self.present(imagePicker, animated: true)
    }

    let libraryAction = UIAlertAction(title: "Photo Library", style: .default) { _ in
      imagePicker.sourceType = .photoLibrary
      imagePicker.allowsEditing = true
      self.present(imagePicker, animated: true)
    }

    let cancelAction = UIAlertAction(title: "Cancel",
                                     style: .cancel,
                                     handler: nil)

    prompt.addAction(camerAction)
    prompt.addAction(libraryAction)
    prompt.addAction(cancelAction)

    present(prompt, animated: true) {
      // Prevent closing the prompt by touch up outside the prompt.
      prompt.view.superview?.subviews[0].isUserInteractionEnabled = false
    }

  }

我尝试通过在UIAlertController方法中使用此代码来设置promptPhoto()的宽度，但无济于事。

let width: NSLayoutConstraint = NSLayoutConstraint(item: prompt.view!,
                                                   attribute: NSLayoutConstraint.Attribute.width,
                                                   relatedBy: NSLayoutConstraint.Relation.equal,
                                                   toItem: nil,
                                                   attribute: NSLayoutConstraint.Attribute.notAnAttribute,
                                                   multiplier: 1,
                                                   constant: self.view.frame.width) 

prompt.view.addConstraint(width)

是否有一种方法可以控制UIAlertController的宽度，以便摆脱错误消息？

谢谢。

Answer 1

这可能是Xcode的错误。苹果仍然没有解决。此错误也是最近发生的xcode 11.3.1