PDFViewer Loading New Document Does Not Display

[michael schroeder]

I am working on a Windows Forms Application that automatically loads a PDF file and then scrolls through the pages.  I am using 2 timers, one to scroll the page, and the other to check for a new version of the PDF file.  When I find a new version of the PDF file, I unload the current file and then load the new file.  All of this appears to work.  The problem is that the document does not appear unless I click on the form.  I can see the scroll bar moving.

Here is the subroutine that loads the document:

    Private Sub LoadPDFFile()

        If File.Exists(My.Settings.PDFFileName) Then
            mCurrrentFileInfo = My.Computer.FileSystem.GetFileInfo(My.Settings.PDFFileName)

            If PdfViewer.IsLoaded Then
                PdfViewer.UnloadDocument()
            End If

            PdfViewer.LoadDocument(My.Settings.PDFFileName)
            PdfViewer.PdfViewerElement.GoToPage(1)
        End If

    End Sub


OS: Windows 8
.Net 4.5
PDFViewer Version: 2014.2.715.40

[George]

Hello Michael,

Thank you for writing.

I tried to load a pdf file using a timer but was not able to reproduce the described behavior locally. I guess that there is something specific to your code and/or pdf file. Can you provide me with a sample project which reproduces the problematic behavior so I can properly investigate it locally.

Looking forward to your reply.

Regards,
George
Telerik

 

 

[michael schroeder]

I attempted to duplicate the problem on my development machine, but was not able to.  So I took the new version of the code up to my client's server.  When I run the code on their server the page does not scroll.  The vertical scroll bar is moving, but the screen is not updating.  In the attached zip file I have included the code along with a short video that shows the problem on my client's server.  in the video notice the scroll bar moving and the document not.  At around the 15 second mark I click in the body of the document.  When I do this the page updates.  At around the 28 second mark I resize the window out of view of the recording, and the document updates.

The video file name is DemoPDFViewer.mp4.

It looks like I can't attach a zip file.  Can I email the file to you?

[michael schroeder]

Hi George,

Here is a link to the zip file https://files.secureserver.net/0stcqHfGPAJ7hk.  The ZIP file contains the VS project and the video that shows the problem.

If there are any questions, please let me know.

Regards
Michael Schroeder

[George]

Hi Michael,

Thank you for writing.

I tried your project, however on my end it seems to be working fine. I tried with the file attached below. Can you check it on your end? Possibly you can give me some more information about the steps I need to take to reproduce the problematic behavior? Alternatively, you can try to invoke the UpdateLayout method after you have scrolled:

PdfViewer.PdfViewerElement.UpdateLayout()

Looking forward to your reply.

Regards,
George
Telerik

 

 

[michael schroeder]

Hi George,

I added the call to PdfViewer.PdfViewerElement.UpdateLayout in the subroutine that scrolls the page.  I also tried using the XML document that you provided.  This works on my development machine, but does not work on my clients machine.  I can see the scroll bar moving.  If I click on the body of the pdf file or resize the window, the document updates the display.

Here is the code:

Private Sub ScrollPageTimerEvent(source As Object, e As ElapsedEventArgs)

        Dim iCurrentPage As Integer
        Dim iPreviousPage As Integer

        Try
            oScrollPageTimer.Stop()

            iPreviousPage = PdfViewer.PdfViewerElement.CurrentPage.PageNo

            PdfViewer.PdfViewerElement.PageDown()

            iCurrentPage = PdfViewer.PdfViewerElement.CurrentPage.PageNo

            If iPreviousPage <> 0 And iCurrentPage = iPreviousPage Then
                PdfViewer.PdfViewerElement.GoToPage(1)
            End If

            PdfViewer.PdfViewerElement.UpdateLayout 

            oScrollPageTimer.Start()

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub

The client is running Windows Server 2008 R2 Standard with SP1.

[George]

Hello Michael,

Thank you for your reply.

I was able to identify the problem in your project. It seems that you are using timers from the System.Timers namespace which is not compatible with WinForms since they run in a different thread, that is why they are not suitable for updating the UI. Please, use Timer from the System.Windows.Forms namespace, this way you should not observe such behavior.

I hope this helps.

Regards,
George
Telerik

 

 

[michael schroeder]

Hi George,

I made the changes and that did resolve the problem.

I want to thank you for your outstanding support!

Regards
Michael Schroeder