imageview 未相应更新

Posted 2023-03-16

【中文标题】imageview 未相应更新

【英文标题】：imageview not updated accordingly

【发布时间】：2018-12-09 03:37:46

【问题描述】：

我想创建一个带有从照片库中选择的照片的图像视图，并通过按下按钮在滚动视图中显示。但是选择后图像不显示，而仅在我再次按下按钮时才显示。有人可以帮我解决这个问题吗？

@IBAction func imageBtnPressed(_ sender: Any) 

    imagePicker()

    let imageView = UIImageView(frame: CGRect(x: (scrollView.bounds.size.width-200)/2, y:(scrollView.bounds.size.height-100)/2, width: 200, height: 100))
    imageView.image = imageOnCanvas
    imageView.contentMode = .scaleAspectFill
    imageView.clipsToBounds = true
    scrollView.addSubview(imageView)




func imagePicker()
    let imagePicker = UIImagePickerController()
    imagePicker.delegate = self
    imagePicker.sourceType = .photoLibrary
    imagePicker.allowsEditing = false
    present(imagePicker, animated: true, completion: nil)



func imagePickerControllerDidCancel(_ picker: UIImagePickerController)

    dismiss(animated: true, completion: nil)



func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) 

    let selectedImage = info[.originalImage] as? UIImage
    imageOnCanvas = selectedImage
    dismiss(animated: true, completion: nil)

【参考方案1】：

您的代码不会因为 UIImagePickerController 出现而暂停。那么，让我们看看你的代码：

@IBAction func imageBtnPressed(_ sender: Any) 
    imagePicker()
    let imageView = UIImageView(frame: CGRect(x: (scrollView.bounds.size.width-200)/2, y:(scrollView.bounds.size.height-100)/2, width: 200, height: 100))
    imageView.image = imageOnCanvas
    imageView.contentMode = .scaleAspectFill
    imageView.clipsToBounds = true
    scrollView.addSubview(imageView)

func imagePicker()
    let imagePicker = UIImagePickerController()
    imagePicker.delegate = self
    imagePicker.sourceType = .photoLibrary
    imagePicker.allowsEditing = false
    present(imagePicker, animated: true, completion: nil)

这正是就像说（用imagePicker函数的内容代替函数调用）：

@IBAction func imageBtnPressed(_ sender: Any) 
    let imagePicker = UIImagePickerController()
    imagePicker.delegate = self
    imagePicker.sourceType = .photoLibrary
    imagePicker.allowsEditing = false
    present(imagePicker, animated: true, completion: nil)
    let imageView = UIImageView(frame: CGRect(x: (scrollView.bounds.size.width-200)/2, y:(scrollView.bounds.size.height-100)/2, width: 200, height: 100))
    imageView.image = imageOnCanvas
    imageView.contentMode = .scaleAspectFill
    imageView.clipsToBounds = true
    scrollView.addSubview(imageView)

嗯，你可以清楚地看到，你指的是imageOnCanvas，它还没有被设置。 imagePicker 仍在显示；用户尚未选择照片。但是你的代码已经完全结束了。您继续添加了一个子视图，该子视图由包含 imageOnCanvas 中的图像的图像视图组成在代码开始之前。

【讨论】：

确实如此。基本上，当您得到用户选择的照片 时，需要将更新滚动视图的调用移至didFinishPickingMediaWithInfo。在那之前，没有什么可以更新的。