Question

由于NSCache已更改为泛型类型NSCache Now，因此这是我正在执行的代码段然而，控制台正在打印 - “After Image To Cache”＆amp;调度主队列CustomImageView但是执行的缓存中的图像没有显示在那里!!也许它没有存储在我正在创建的缓存中！有帮助吗？将不胜感激

let imageCache = NSCache<AnyObject, AnyObject>()

类CustomImageView：UIImageView { var imageURLString：String？

func loadImageUsingURlString(urlString: String)
{
    imageURLString = urlString

    let url = URL(string: urlString)

    image = nil
    if let imageFromCache = imageCache.object(forKey: urlString as AnyObject ) as? UIImage
    {
        self.image = imageFromCache
        print("Image From Cache Executed")
        return
    }



    URLSession.shared.dataTask(with: url!, completionHandler:
    {
        (data, response, error) in

        if error != nil
        {
            print(error ?? "loadImageUsingURlString | Class : Helpers -> CustomImageView")
            return
        }

        DispatchQueue.main.async
        {
            let imageToCache = UIImage(data: data!)
            print("After Image To Cache")


            if self.imageURLString == urlString
            {
                print("Dispatch Main Queue CustomImageView[![enter image description here][1]][1]")
                self.image = imageToCache

            }
            else
            {
                        imageCache.setObject(imageToCache!, forKey: urlString as AnyObject)
            }



        }

    }).resume()
}

}

Answer 1

首先：

let imageCache = NSCache<AnyObject, AnyObject>()为什么您在此使用AnyObject而不是您正在使用的类型String和UIImage。您在代码中有不必要的转换。

第二个想法：

if self.imageURLString == urlString
            {
                print("Dispatch Main Queue CustomImageView[![enter image description here][1]][1]")
                self.image = imageToCache

            }
            else
            {
                        imageCache.setObject(imageToCache!, forKey: urlString as AnyObject)
            }

如果网址匹配，则不会缓存图片。您应该删除else并让imageCache.setObject(imageToCache!, forKey: urlString as AnyObject)始终在异步调用后执行。

顺便说一下，总是使用更好的开发人员编写和测试过的代码:) 试试这个：Kingfisher

Answer 2

我认为if self.imageURLString == urlString条件不是必需的，您能否尝试下面的代码，它对我来说是完美的？

let imageCache = NSCache<NSString, UIImage>()

extension UIImageView {

    func loadImageCacheWithUrlString(urlString: String) {

        if let cachedImage = imageCache.object(forKey: urlString as NSString){
            self.image = cachedImage
            return
        }

        URLSession.shared.dataTask(with: URL(string: urlString)!) { (data, response, error) in
            if error != nil {
                return
            }
            DispatchQueue.main.async {
                if let downloadedImage = UIImage(data: data!) {
                    imageCache.setObject(downloadedImage, forKey: urlString as NSString)
                    self.image = downloadedImage
                }
            }
            }.resume()
    }
}

NSCache无法正常工作，无法从缓存加载图像

2 个答案: