Xamarin-CrossDownloadManager - 等待下载文件

Question

我使用 Xamarin-CrossDownloadManager ( https://github.com/SimonSimCity/Xamarin-CrossDownloadManager )，我需要等待下载文件。我有这段代码:

private static async Task<bool> FileDownloadedTest(string LinkToFile, string PathFile)
    {
        var downloadManager = CrossDownloadManager.Current;
        CrossDownloadManager.Current.PathNameForDownloadedFile = new System.Func<IDownloadFile, string>(file => {
            return PathFile;
        });
        {
            await DeleteFile(PathFile);
            var file = downloadManager.CreateDownloadFile(LinkToFile);
            await Task.Run(() => downloadManager.Start(file, true)); //why this not wait???
        }         
        bool FileExist = await IsFileExist(PathFile);
        return FileExist;    
    }

为什么不等待完成下载操作？怎么做？

他们在图书馆网站上写道，我可以在下载文件时查看 IDownloadManager.Queue 以获取信息。但是，我不知道如何在我的方法中使用它...你能帮帮我吗？

PS:抱歉我的英语不好，我还在学习 ;)

Answer 1

使用该库，当文件下载完成时不会发布回调或事件，但您可以执行一个简单的检查并等待更多循环。

await Task.Run(async () =>
{
    var downloadManager = CrossDownloadManager.Current;
    var file = downloadManager.CreateDownloadFile(someFileBasedUrl);
    downloadManager.Start(file);
    bool isDownloading = true;
    while (isDownloading)
    {
        await Task.Delay(10 * 1000);
        isDownloading = IsDownloading(file);
    }
});

IsDownloading 方法:

bool IsDownloading(IDownloadFile file)
{
    if (file == null) return false;

    switch (file.Status)
    {
        case DownloadFileStatus.INITIALIZED:
        case DownloadFileStatus.PAUSED:
        case DownloadFileStatus.PENDING:
        case DownloadFileStatus.RUNNING:
            return true;

        case DownloadFileStatus.COMPLETED:
        case DownloadFileStatus.CANCELED:
        case DownloadFileStatus.FAILED:
            return false;
        default:
            throw new ArgumentOutOfRangeException();
    }
}

回复:https://github.com/SimonSimCity/Xamarin-CrossDownloadManager/blob/develop/Sample/DownloadExample/Downloader.cs#L46