It seems that adding an event handler to any of the Download events (DownloadCancelled, DownloadCompleted, DownloadProgressChanged) throws a NullReferenceException in InternalDownloadHandler.OnDownloadUpdated, the problem appears to be with the CefDownloadItem! The CefDownloadItem is being Disposed() before OnDownloadUpdated can use it. To my pleasant surprise downloads work perfectly fine as fire and forget operations (not using DownloadCancelled, DownloadCompleted, DownloadProgressChanged); however, for my use case I really need to be able to track the download so I did a little debugging.

I believe that a simple change to WebView.InternalDownloadHandler like below will solve the problem:

protected override void OnDownloadUpdated(CefBrowser browser, CefDownloadItem downloadItem, CefDownloadItemCallback callback) 
{
    var fullPath = downloadItem.FullPath;
    var receivedBytes = downloadItem.ReceivedBytes;
    var totalBytes = downloadItem.TotalBytes;

    if (downloadItem.IsComplete) {
        if (OwnerWebView.DownloadCompleted != null) {
            OwnerWebView.AsyncExecuteInUI(() => OwnerWebView.DownloadCompleted?.Invoke(fullPath));
        }
    } else if (downloadItem.IsCanceled) {
        if (OwnerWebView.DownloadCancelled != null) {
            OwnerWebView.AsyncExecuteInUI(() => OwnerWebView.DownloadCancelled?.Invoke(fullPath));
        }
    } else {
        if (OwnerWebView.DownloadProgressChanged != null) {
            OwnerWebView.AsyncExecuteInUI(() => OwnerWebView.DownloadProgressChanged?.Invoke(fullPath, receivedBytes, totalBytes));
        }
    }
}

Thanks and God Bless,
- Dean

Avalonia: How do properly handle file downloads? #379

Description

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions