Question

我一直试图安静地异步加载图像。当我为此创建一个新类并构建并运行该应用程序时，运行时日志中会出现错误

// log
Failed to set (borderWidth) user defined inspected property on ...
could not set nil as the value for the key borderWidth.
could not set nil as the value for the key cornerRadius.

使用扩展名代替类很好，图像将异步加载，但是这样一来，我将无法确保在图像视图中加载了正确的图像。

//  cell for item at
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell  = collectionView.dequeueReusableCell(withReuseIdentifier: "subscribeCell", for: indexPath) as! subscribeViewCell

    cell.userID = self.users[indexPath.row].userId
    cell.profileName.text = self.users[indexPath.row].fullName
    cell.profileImage.setupWithImageUrl(imageUrl: self.users[indexPath.row].ImagePath)
    checkFollowers(indexPath : indexPath)
    return cell
}

我在同一视图控制器中使用过的类：

要下载图像的类：

private var imageCache = [String:UIImage]()

class CustomImageView : UIImageView {

    var lastImageUrl : String?

    func setupWithImageUrl (imageUrl: String) {

        self.contentMode = .scaleAspectFill
        self.clipsToBounds = true
        self.layer.cornerRadius = 14
        self.layer.borderWidth = 0

        lastImageUrl = imageUrl
        if let cachedImage = imageCache[imageUrl] {
            self.image = cachedImage
            return
        }
        guard let url = URL(string: imageUrl) else {
            return
        }
        URLSession.shared.dataTask(with: url) { (data, response, error) in
            if let error = error {
                print(error)
                return
            }
            guard let data = data else {
                return
            }
            guard let image = UIImage(data : data) else {
                return
                }
            imageCache[url.absoluteString] = image
            }
            if (url.absoluteString != self.lastImageUrl) {
            return
            }
            DispatchQueue.main.async {
                self.image = self.image
            }
        }
    }

Answer 1

为什么“通过这种方式”不能确保将正确的图像加载到图像视图中。我阅读了您的代码，我认为您的代码适合collectionViewController cellForItemAt

从Firebase异步加载图像时出错

1 个答案: