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我正在尝试将文件从 Java Spring 后端下载到我的 Xamarin Forms 应用程序。我正在使用本机 Android 管理器。当我开始下载时，我在 Files 中看到了新文件，很快就开始下载，最终达到 100%。之后，文件立即进入排队状态。一段时间后，它说下载不成功。当我读取状态时，原因码是 1008，这意味着 ERROR_CANNOT_RESUME。但是，如果下载达到 100%，还有什么要恢复的呢？这只发生在 Android 9 上，我尝试了 7 和 8.1，它没有任何错误。

Xamarin 代码：

public long download(string url, string filePath, string token) {
        var manager = (Android.App.DownloadManager)Android.App.Application.Context.GetSystemService(Context.DownloadService);
        var source = Android.Net.Uri.Parse(url);
        var request = new DownloadManager.Request(source);
        request.AllowScanningByMediaScanner();
        request.SetNotificationVisibility(DownloadVisibility.VisibleNotifyCompleted);
        //request.SetDestinationInExternalPublicDir(Android.OS.Environment.DirectoryDownloads, source.LastPathSegment);

        request.AddRequestHeader("Authorization", "Bearer " + token);
        request.AddRequestHeader("Content-type", "application/octet-stream");

        long downloadId = manager.Enqueue(request);

        return downloadId;
    }

Java后端代码：

@RequestMapping(path = "/download/{idBook}/{idDevice}", method = RequestMethod.GET, produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
public void download(@PathVariable int idBook, @PathVariable String idDevice, HttpServletRequest request, HttpServletResponse response) throws Exception     
{
    String rangestring = request.getHeader("Range");
    //System.out.println(rangestring);
    if(rangestring != null)
    {
        String[] strings = (rangestring.substring(6)).split("-");
    }
    
    Book book = myBookRepository.getOne(idBook);
    
    String fileName = fileUtil.getFilePath(idBook);
    
    MultipartFileSender.fromFile(new File(fileName))
            .with(request)
            .with(response)
            .serveResource();
}

MultipartFileSender 取自这里

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