Brad Brad - 1 month ago 10
C# Question

c# flickering Listview on update

I have a list view that is periodically updated (every 60 seconds). It was anoying to me that i would get a flicker every time it up dated. The method being used was to clear all the items and then recreate them. I decided to instead of clearing the items I would just write directly to the cell with the new text. Is this a better approach or does anyone have a better solution.

Answer

The ListView control has a flicker issue. The problem appears to be that the control's Update overload is improperly implemented such that it acts like a Refresh. An Update should cause the control to redraw only its invalid regions whereas a Refresh redraws the control’s entire client area. So if you were to change, say, the background color of one item in the list then only that particular item should need to be repainted. Unfortunately, the ListView control seems to be of a different opinion and wants to repaint its entire surface whenever you mess with a single item… even if the item is not currently being displayed. So, anyways, you can easily suppress the flicker by rolling your own as follows:

class ListViewNF : System.Windows.Forms.ListView
{
    public ListViewNF()
    {
        //Activate double buffering
        this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);

        //Enable the OnNotifyMessage event so we get a chance to filter out 
        // Windows messages before they get to the form's WndProc
        this.SetStyle(ControlStyles.EnableNotifyMessage, true);
    }

    protected override void OnNotifyMessage(Message m)
    {
        //Filter out the WM_ERASEBKGND message
        if(m.Msg != 0x14)
        {
            base.OnNotifyMessage(m);
        }
    }
}

From: Geekswithblogs.net

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