ios - xcode View 不显示 url 图片

Question

我正在学习斯坦福大学的 iOS 开发类(class)，并将类(class)中运行良好的示例代码复制到我的 Xcode 中。该 View 只是不显示 url 图像，我已经将信息中的允许任意加载设置为"is"。屏幕上没有出现任何错误，但 View 没有显示任何内容。

  class ImageViewController: UIViewController

    {

    var imageURL: URL? {
       didSet {
         image = nil
            if view.window != nil {
             fetchImage()
            }
        }
    }

    private func fetchImage() {
         if let url = imageURL {
         let urlContents = try? Data(contentsOf: url)
           if let imageData = urlContents {
              image = UIImage(data: imageData)
           }
        }
    }

override func viewDidLoad() {
    super.viewDidLoad()
    imageURL = DemoURL.stanford // for demo/testing purposes only 


 //This is the url image. It is in another swift file，the address is ( static let stanford = URL(string: "http://stanford.edu/about/images/intro_about.jpg"，) I can open it in safari.

}

override func viewWillAppear(_ animated: Bool) {
   super.viewWillAppear(animated)
    if image == nil { // we're about to appear on screen so, if needed,
      fetchImage() // fetch image
    }
}


fileprivate var imageView = UIImageView()
private var image: UIImage? {
       get {
          return imageView.image
         }
       set {
      imageView.image = newValue
      imageView.sizeToFit()
    // careful here because scrollView might be nil
    // (for example, if we're setting our image as part of a prepare)
    // so use optional chaining to do nothing
      // if our scrollView outlet has not yet been set

     }
   }
} 

提前致谢。

Answer 1

DemoURL.swift 中的 URL 不存在...例如，您可以在 DemoURL.swift 中写入:

static let stanford = URL(string:"http://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Stanford_Oval_May_2011_panorama.jpg/800px-Stanford_Oval_May_2011_panorama.jpg")