uwp - 如何在 BackgroundTransfer 中处理进度 DownloadOperation C++/WinRT

Question

我尝试通过 c++/WinRT Windows 10 UWP App 中的 BackgroundTransfer::BackgroundDownloader 处理下载文件的进度。

我昨天阅读了 10 次文档： https ://docs.microsoft.com/en-us/uwp/api/windows.foundation.iasyncoperationwithprogress-2.progress?view=winrt-19041#Windows_Foundation_IAsyncOperationWithProgress_2_Progress

但我不能正确地实现这个:(

这是我的示例代码（文件下载好，但如果我把 .Progress 函数我得到错误： Error C2280 'void *winrt::Windows::Foundation::IUnknown::operator new(size_t)': attempting to reference a deleted function NativeModuleSample

代码：

BackgroundTransfer::BackgroundDownloader downloader{ BackgroundTransfer::BackgroundDownloader() };
BackgroundTransfer::DownloadOperation download = downloader.CreateDownload(uri, destinationFile);
auto progress = download.StartAsync();

progress.Progress(Windows::Foundation::AsyncOperationProgressHandler<BackgroundTransfer::DownloadOperation, BackgroundTransfer::BackgroundDownloadProgress>(
    [=](Windows::Foundation::IAsyncOperationWithProgress<BackgroundTransfer::DownloadOperation, BackgroundTransfer::DownloadOperation> const sender, BackgroundTransfer::BackgroundDownloadProgress args) {
        int progress_calc = (int)(100 * ((double)args.BytesReceived / (double)args.TotalBytesToReceive));    
    }
));

标签： uwpc++-winrt

Answer 1

通过 BackgroundTransfer::BackroundDownloader 处理下载文件的进度，可以参考GitHub中示例的 Scenario1_Download。

根据有关下载的示例，您可以将代码更改progress.Progress(…) 为：

progress.Progress(Windows::Foundation::AsyncOperationProgressHandler<Windows::Networking::BackgroundTransfer::DownloadOperation, Windows::Networking::BackgroundTransfer::DownloadOperation>(
    [=](Windows::Foundation::IAsyncOperationWithProgress<Windows::Networking::BackgroundTransfer::DownloadOperation, Windows::Networking::BackgroundTransfer::DownloadOperation> const sender, 
        Windows::Networking::BackgroundTransfer::DownloadOperation args) {
               
            BackgroundDownloadProgress currentProgress = args.Progress();

            UINT64 percent = 0;
            if (currentProgress.TotalBytesToReceive > 0)
            {
                percent =(INT64)((double)currentProgress.BytesReceived * 100 / (double)currentProgress.TotalBytesToReceive);
            }
    }
));