Question

我想使用AlamofireImage从网址下载图片，然后将其缓存在设备磁盘空间中。我阅读了几篇关于此的帖子，发现AlamofireImage在ImageDownloader类的帮助下支持这一点。最有趣的信息是in this SO answer

因此，我尝试为ImageDownloader设置自定义NSURLCache，以便将图像直接缓存到磁盘。我通过将内存容量设置为0来实现。然后我使用此自定义ImageDownloader下载图像。我为磁盘路径指定的文件夹是在磁盘上创建的，但遗憾的是它保持为空并且图像不会以任何方式缓存。

**编辑：**请注意，缓存的响应不会保存在缓存目录的文件夹中，而是保存在文件夹旁边的数据库文件中。

有谁能告诉我这里做错了什么？非常感谢阅读！

func diskImageDownloader(diskSpaceMB: Int = 100) -> ImageDownloader {

    let diskCapacity = diskSpaceMB * 1024 * 1024
    let diskCache = NSURLCache(memoryCapacity: 0, diskCapacity: diskCapacity, diskPath: "alamofireimage_disk_cache")
    let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
    configuration.URLCache = diskCache
    let downloader = ImageDownloader(configuration: configuration)
    UIImageView.af_sharedImageDownloader = downloader

    return downloader
}

func getProfileImage(atURL url: String, onComplete: SRServiceResponse<UIImage> -> Void) {
    guard let imageURL = NSURL(string: url) else
    {
        // TODO: Fail here
        return
    }

    let request = NSURLRequest(URL: imageURL)

    let imageDownloader = self.diskImageDownloader()

    imageDownloader.downloadImage(URLRequest: request) { (response) in
        switch response.result
        {
        case .Success(let image):
            // Do something
        case .Failure(let error):
            // Do something
        }
    }
}

Answer 1

我没有为代表这样做。只是为了节省编译时间。

在 Swift 3.0

中

class DiskCache: URLCache {


  private let constSecondsToKeepOnDisk = numDaysToKeep*24*60*60 // numDaysToKeep is your own constant or hard-coded value

  override func storeCachedResponse(_ cachedResponse: CachedURLResponse, for request: URLRequest) {

    var customCachedResponse = cachedResponse
    // Set custom Cache-Control for Image-Response
    let response = cachedResponse.response as! HTTPURLResponse

    if let contentType = response.allHeaderFields["Content-Type"] as? String,
        var newHeaders = response.allHeaderFields as? [String: String], contentType.contains("image") {
        newHeaders["Cache-Control"] = "public, max-age=\(constSecondsToKeepOnDisk)"
        if let url = response.url, let newResponse = HTTPURLResponse(url: url, statusCode: response.statusCode, httpVersion: "HTTP/1.1", headerFields: newHeaders) {
            customCachedResponse = CachedURLResponse(response: newResponse, data: cachedResponse.data, userInfo: cachedResponse.userInfo, storagePolicy: cachedResponse.storagePolicy)
        }
    }
    super.storeCachedResponse(customCachedResponse, for: request)
  }
}

Answer 2

要实现您的目标，请将您用作diskCache的NSURLCache真正自定义，以便为存储的图片设置您自己的到期日期：

class DiskCache: NSURLCache {
    private let constSecondsToKeepOnDisk = 30*24*60*60 // 30 days

    override func storeCachedResponse(cachedResponse: NSCachedURLResponse, forRequest request: NSURLRequest) {
        var customCachedResponse = cachedResponse
        // Set custom Cache-Control for Image-Response
        if let response = cachedResponse.response as? NSHTTPURLResponse,
            let contentType = response.allHeaderFields["Content-Type"] as? String,
            var newHeaders = response.allHeaderFields as? [String: String] where contentType.containsString("image") {
            newHeaders["Cache-Control"] = "public, max-age=\(constSecondsToKeepOnDisk)"
            if let url = response.URL, newResponse = NSHTTPURLResponse(URL: url, statusCode: response.statusCode, HTTPVersion: "HTTP/1.1", headerFields: newHeaders) {
                customCachedResponse = NSCachedURLResponse(response: newResponse, data: cachedResponse.data, userInfo: cachedResponse.userInfo, storagePolicy: cachedResponse.storagePolicy)
            }
        }
        super.storeCachedResponse(customCachedResponse, forRequest: request)
    }
}

每次您可以重复使用共享实例来调用ImageDownloader方法时，而不是创建新的downloadImage：UIImageView.af_sharedImageDownloader.downloadImage(URLRequest: request)

AlamofireImage磁盘缓存无法正常工作

2 个答案: