Question

我的collectionView控制器中有一些加载问题。当我上传视频时，它将制作该视频的屏幕截图，然后将其缓存，因此不会再次下载。当滚动滚动上载新视频时，缓存可以完美地工作，它将冻结整个滚动，因此可以下载新的视频屏幕截图。我有做“事后技巧”的波纹管功能。我还试图结合第二个功能在下载完成后触发此功能，但是我不知道该如何使它工作。

func previewImageFromVideo(url: NSURL) -> UIImage? {
    let url = url as URL
    let request = URLRequest(url: url)
    let cache = URLCache.shared

    if
        let cachedResponse = cache.cachedResponse(for: request),
        let image = UIImage(data: cachedResponse.data)
    {
        return image
    }

    let asset = AVAsset(url: url)
    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true
    imageGenerator.maximumSize = CGSize(width: 500, height: 500)

    var time = asset.duration
    time.value = min(time.value,2)

    var image: UIImage?

    do {
        let imageRef = try imageGenerator.copyCGImage(at: time, actualTime: nil)
        image = UIImage(cgImage: imageRef)
    } catch { }

    if
        let image = image,
        let pngData = UIImagePNGRepresentation(image)
    {
        let response = HTTPURLResponse(url: url, statusCode: 200, httpVersion: nil, headerFields: nil)!
        let cachedResponse = CachedURLResponse(response: response, data: pngData)

        cache.storeCachedResponse(cachedResponse, for: request)
    }

    return image
}

这是开始下载文件和强制功能，它将告诉我何时完成：

//SESSION URL - DOWNLOAD WITH PROGRESS
func beginDownloadingFile(urlString: String) {
    print("Attempting to download file")

    let configuration = URLSessionConfiguration.default
    let operationQueue = OperationQueue()
    let urlSession = URLSession(configuration: configuration, delegate: self, delegateQueue: operationQueue)

    guard let url = URL(string: urlString) else { return }
    let downloadTask = urlSession.downloadTask(with: url)

    downloadTask.resume()
}

//DOWNLOAD WITH PROGRESS - BASIC APPROACH
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    print("Finished downloading file")


}

从服务器制作视频截图时，Collection View滚动冻结

0 个答案: