wpf window refresh works at first, then stops
- by mcl
I've got a routine that grabs a list of all images in a directory, then runs an MD5 digest on all of them. Since this takes a while to do, I pop up a window with a progress bar. The progress bar is updated by a lambda that I pass in to the long-running routine.
The first problem was that the progress window was never updated (which is normal in WPF I guess). Since WPF lacks a Refresh() command I fixed this with a call to Dispatcher.Invoke(). Now the progress bar is updated for a while, then the window stops being updated. The long-running work does eventually finish and the windows go back to normal.
I have already tried a BackgroundWorker and quickly became frustrated by a threading issue related to an event triggered by the long-running process. So if that's really the best solution and I just need to learn the paradigm better, please say so.
But I'd be really much happier with the approach I've got here, except that it stops updating after a bit (for example, in a folder with 1000 files, it might update for 50-100 files, then "hang"). The UI does not need to be responsive during this activity, except to report on progress.
Anyway, here's the code. First the progress window itself:
public partial class ProgressWindow : Window
{
public ProgressWindow(string title, string supertext, string subtext)
{
InitializeComponent();
this.Title = title;
this.SuperText.Text = supertext;
this.SubText.Text = subtext;
}
internal void UpdateProgress(int count, int total)
{
this.ProgressBar.Maximum = Convert.ToDouble(total);
this.ProgressBar.Value = Convert.ToDouble(count);
this.SubText.Text = String.Format("{0} of {1} finished", count, total);
this.Dispatcher.Invoke(DispatcherPriority.Render, EmptyDelegate);
}
private static Action EmptyDelegate = delegate() { };
}
<Window x:Class="Pixort.ProgressWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Pixort Progress" Height="128" Width="256" WindowStartupLocation="CenterOwner" WindowStyle="SingleBorderWindow" ResizeMode="NoResize">
<DockPanel>
<TextBlock DockPanel.Dock="Top" x:Name="SuperText" TextAlignment="Left" Padding="6"></TextBlock>
<TextBlock DockPanel.Dock="Bottom" x:Name="SubText" TextAlignment="Right" Padding="6"></TextBlock>
<ProgressBar x:Name="ProgressBar" Height="24" Margin="6"/>
</DockPanel>
</Window>
The long running method (in Gallery.cs):
public void ImportFolder(string folderPath, Action<int, int> progressUpdate)
{
string[] files = this.FileIO.GetFiles(folderPath);
for (int i = 0; i < files.Length; i++)
{
// do stuff with the file
if (null != progressUpdate)
{
progressUpdate.Invoke(i + 1, files.Length);
}
}
}
Which is called thusly:
ProgressWindow progress = new ProgressWindow("Import Folder Progress", String.Format("Importing {0}", folder), String.Empty);
progress.Show();
this.Gallery.ImportFolder(folder, ((c, t) => progress.UpdateProgress(c, t)));
progress.Close();
