AlamofireImage磁盘缓存无法正常工作

Question

我想使用AlamofireImage从URL下载图像,然后将其缓存在设备磁盘空间.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.在这个SO答案中给出了最有趣的信息

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,但不幸的是它保持为空并且图像不会以任何方式缓存.

**编辑:**重要的是要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.

谁能告诉我这里我做错了什么？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

我不是这样做的代表.只是为了节省编译器的时间.

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

为了实现您的目标，请NSURLCache真正自定义用作 diskCache 的磁盘缓存，以设置您自己的存储图像的到期日期：

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)
    }
}

您可以重用共享实例来调用该方法，而不是ImageDownloader每次都创建一个新实例downloadImage：UIImageView.af_sharedImageDownloader.downloadImage(URLRequest: request)