ios - 将 AlamofireImage 响应缓存到磁盘

Question

我需要一些有关 AlamofireImages 的帮助。在应用程序中，点击表格 View 单元格将使用内置的 ImageView 扩展下载并设置图像，如下所示:

func sendImageRequest(imageView: UIImageView, item: CatalogItem, isLargeImage: Bool? = false){
    let imageURL = ImageManager.URLBuilder(sku: item.sku, largeImage: isLargeImage)

    // Clear the image so that recycled images are cleared.
    imageView.image = nil

    // Create the request and add the token string to the authorization header
    var urlRequest = try! URLRequest(url: URL(string: imageURL)!)
    urlRequest.setValue("Bearer \(ImageManager.getTokenString()!)", forHTTPHeaderField: "Authorization")

    // If the token exists AND is VALID (not expired) - Get the image.
    if ImageManager.checkIfTokenExists() && ImageManager.checkTokenIsValid(){
        debugPrint("Valid token already exists. Fetching image... TableViewExtension")
        imageView.af_setImage(withURLRequest: urlRequest){ response in
            switch response.result{
            case .success(let image):
                debugPrint(response)
                debugPrint("SUCCESS")
                break
            case .failure(let error):
                debugPrint("Error: \(error)")
                debugPrint(response.response)
                break
            }
        }
    }
    // Else if the token exists AND is INVALID (expired) - Delete the old token, get a new one, and fetch the image
    else if ImageManager.checkIfTokenExists() && !ImageManager.checkTokenIsValid(){
        debugPrint("Token expired... Getting new token.")
        ImageManager.deleteToken()
        let tokenRequest = NetRequest.newTokenRequest(url: "http://\(SettingsManager.KEY_ServerURL).ziizii.io/zz/jwt/new?service=images.ziizii.io")
        tokenRequest.requestJWTToken(){
            debugPrint("Token renewed. Fetching image...")
            imageView.af_setImage(withURLRequest: urlRequest)
        }
    }
    // If the token doesn't exist, request a new one and fetch the image.
    else{
        debugPrint("Requesting new token...")
        let tokenRequest = NetRequest.newTokenRequest(url: "http://\(SettingsManager.KEY_ServerURL).ziizii.io/zz/jwt/new?service=images.ziizii.io")
        tokenRequest.requestJWTToken(){
            debugPrint("Token aquired. Fetching image...")
            imageView.af_setImage(withURLRequest: urlRequest)
        }
    }
}

所以，这部分我没问题。它可以工作，它将对象缓存到磁盘并设置 ImageView 图像。如果您稍后再次点击它，它会检查图像是否在缓存中，如果是，则只需应用该图像。整洁。

现在，该项目的一个新要求是让用户能够预加载每个图像并缓存它们。现在我不再使用 AFI ImageView 扩展，而是使用下载器。我不确定如何让下载器:A)缓存到磁盘和B) 当用户点击单元格时，让 ImageView 扩展检查相同的缓存以查看它是否已预加载并应用该图像。

AFI 足够聪明，可以在发送请求之前检查图像数据的缓存，因此我确信这是可能的。

到目前为止我下载的图像如下:

static var downloader = ImageDownloader.default

static func downloadImage(urlRequest: URLRequestConvertible)
{
    self.downloader.download(urlRequest) { response in
        switch response.result{
        case .success(let image): // If successful, cache the image.
            print("SUCCESS")
            break
        case .failure(let error): // If unsuccessful, remove the cached 404 response and apply a nil image.
            print("ERROR: \(response.error)")
            break
        }
    }
}

如果有人知道如何实现此目的或任何有用的提示或技巧，那就太好了!谢谢!

Answer 1

好吧，我假设您正在从字符串中下载图像作为下载网址。我也处理过同样的问题；就我而言，我没有使用 Alamofire，我使用的是 ImageView 的扩展:

let imageCache = NSCache<AnyObject, AnyObject>()

扩展 UIImageView {

func downloadImage(from imgURL: String!) {

    self.image = nil

    // Check if there's an image in the cache 

    if let cachedImage = imageCache.object(forKey: imgURL as AnyObject) as? UIImage {
        self.image = cachedImage
        return
    }

    // Otherwise, download image from Firebase via URL-string

    let url = URLRequest(url: URL(string: imgURL)!)

    let task = URLSession.shared.dataTask(with: url) {
        (data, response, error) in

        if error != nil {
            print(error!)
            return
        }

        DispatchQueue.main.async {
            if let image = UIImage(data: data!) {
                imageCache.setObject(image, forKey: imgURL as AnyObject)
            }
            self.image = UIImage(data: data!)
        }

    }

    task.resume()
}

}

现在我只需调用即可解决预加载问题

for i in objects { // whatever object you're having

   imageView.downloadImage(fromURL: i.url)

}

...在 viewDidLoad() 中。

现在，它会循环遍历所有自定义对象，下载并缓存所有图像，如果用户点击图像，则会立即从缓存中加载该图像。我希望这能帮助您解决问题。