ImageView 不会更新新图像

Question

我正在尝试 select 来自用户 phone 的图像并使用该图像更新图像视图。

我遇到的问题是它不会更新图像。当我添加一个断点并且它到达断点时它确实到达了那里，并且当我手动尝试在其他地方更改它时图像视图可以更改图像。

但是当我需要它时它拒绝工作。

我的图片浏览：

    lazy var profilePictureImageView: UIImageView = {
        let imageView = UIImageView()
        imageView.image = UIImage(named: "DefaultUser")
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.contentMode = .scaleAspectFill

        imageView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(handleSelectProfilePicture)))
        imageView.isUserInteractionEnabled = true
        return imageView
    }()

通过在设备上选择照片来更新图像的代码：

import UIKit

extension ProfileVC: UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    func handleSelectProfilePicture() {
        let picker = UIImagePickerController()
        picker.delegate = self
        picker.allowsEditing = true
        present(picker, animated: true, completion: nil)
    }

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
         var selectedImageFromPicker: UIImage?
         if let editedImage = info["UIImagePickerControllerEditedImage"] as? UIImage {
             selectedImageFromPicker = editedImage
         }
         else if let originalImage = info["UIImagePickerControllerOriginalImage"] as? UIImage {
             selectedImageFromPicker = originalImage
         }
        if let selectedImage = selectedImageFromPicker {
             profilePictureImageView.image = selectedImage
        }
        dismiss(animated: true, completion: nil)
    }

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        dismiss(animated: true, completion: nil)
    }
}

[编辑] 我发现的一件事是，如果我在具有不同图像视图的不同 VC 上尝试它，它会按预期工作。我能看到的两个 VC 之间唯一的主要区别是我希望它可以工作但不会同时扩展 'UIPickerViewDelegate' 和 'UIPickerViewDataSource' 的那个。会不会有冲突？

Answer 1

您想在主线程上进行所有 UI 更新——例如更改图像：

   if let selectedImage = selectedImageFromPicker {
         DispatchQueue.main.async {
             profilePictureImageView.image = selectedImage
         }
    }

应该做。

Answer 2

我对这段代码没有任何问题，我已尝试尽可能多地复制您的代码。

class ViewController: UIViewController {

    lazy var imageView: UIImageView = {
       let iView = UIImageView()
        iView.contentMode = .scaleAspectFill

        iView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(handleSelectProfilePicture)))
        iView.isUserInteractionEnabled = true
        return iView
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.addSubview(imageView)
        self.imageView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint(item: imageView, attribute: .height, relatedBy: .equal, toItem: self.view, attribute: .height, multiplier: 1.0, constant: 1.0).isActive = true
        NSLayoutConstraint(item: imageView, attribute: .width, relatedBy: .equal, toItem: self.view, attribute: .width, multiplier: 1.0, constant: 1.0).isActive = true
    }

    func handleSelectProfilePicture() {
        let picker = UIImagePickerController()
        picker.delegate = self
        picker.allowsEditing = true
        present(picker, animated: true, completion: nil)
    }
}

extension ViewController: UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {

        var selectedImageFromPicker: UIImage?

        if let editedImage = info["UIImagePickerControllerEditedImage"] as? UIImage {
            selectedImageFromPicker = editedImage
        }

        else if let originalImage = info["UIImagePickerControllerOriginalImage"] as? UIImage {
            selectedImageFromPicker = originalImage
        }

        if let selectedImage = selectedImageFromPicker {
            imageView.image = selectedImage
        }

        dismiss(animated: true, completion: nil)
    }

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        dismiss(animated: true, completion: nil)
    }
}

问题一定是由您的代码中的其他内容引起的。我使用了一个和你一样的惰性变量。您能否尝试将您的代码简化为这个并查看它是否有效或 post 其余代码。您设置了哪些限制条件？

Answer 3

试试这个，它对我有用：

DispatchQueue.main.async {
    profilePictureImageView.image = croppedImage
    profilePictureImageView.setNeedsDisplay()
}

基本上你需要指定你想通过

更新图像

profilePictureImageView.setNeedsDisplay()

Answer 4

尝试将 modalPresentationStyle 设置为 overCurrentContext 喜欢下面的示例

 let myPickerController = UIImagePickerController()
    myPickerController.delegate = self
    myPickerController.sourceType =  UIImagePickerControllerSourceType.photoLibrary
    **myPickerController.modalPresentationStyle = .overCurrentContext**
    myPickerController.delegate = self
    present(myPickerController, animated: true, completion: nil)

Answer 5

这是另一个可能对某人有用的案例：

我遇到了同样的问题，只是我的 ImageView 在 TableViewCell 上。工作在主线程上完成。没有任何工作包括调用 imageView.setNeedsDisplay() 甚至在每个超级视图上。

出于某种奇怪的原因，有帮助的只是在包含 imageView 的 cell 上调用 setNeedsLayout()。我检查了布局，在此调用之前和之后所有视图的顺序和位置都相同。

我不确定为什么会这样，除此之外什么都没有，所以如果有人有任何想法，我们将不胜感激。

Answer 6

我现在自己尝试的方法是进入 UITabBarController，并在 viewDidLoad() 中创建所有 viewControllers，而不是在最初所在的 viewWillAppear() 中.

请注意，您必须使用 dispatch 否则应用程序会崩溃

override func viewDidLoad() {
    super.viewDidLoad()

    DispatchQueue.main.async {
        self.setupViewControllers()
    }
}

看起来是因为 viewController 是在 viewWillAppear() 中创建的，在 uiPicker 关闭后 viewControllers 将再次加载并且所选图像将丢失。

Answer 7

首先使用

将现有图像值设为空

        imageView.image = nil

然后将新图像添加到图像视图

        let yourImage = UIImage(named: "your_image_name")
        imageView.image = yourImage

这对我有用

ImageView 不会更新新图像

ImageView won't update with new image

image

uiimagepickercontroller

ios

swift