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我想用从照片库中选择的照片创建一个图像视图，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)
}
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1 回答 1

1

您的代码不会因为 UIImagePickerController 出现而暂停。所以，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)
}

所以这就像说（用函数的内容代替imagePicker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)
}

好吧，您可以清楚地看到，您指的是imageOnCanvas尚未设置的时间。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。您继续添加一个子视图，该子视图由包含在imageOnCanvas 代码开始之前存在的图像的图像视图组成。

于 2018-12-09T04:00:50.373 回答