How does one implement pull-to-refresh with a LongListSelector in Windows Phone 8?

Question

I am writing a new WP8 app using the off-the-shelf LongListSelector that is shipped in the Microsoft.Phone.Controls assembly. Can anyone provide a code example that implements p

Answer 1

This is not completely trivial, but one way of doing it is to use GestureService

        this.gestureListener = GestureService.GetGestureListener(containerPage);
        this.gestureListener.DragStarted += gestureListener_DragStarted;
        this.gestureListener.DragCompleted += gestureListener_DragCompleted;
        this.gestureListener.DragDelta += gestureListener_DragDelta;

However, it has some bugs. For example, DragCompleted is not always raised, so you need to double-check for that using ManipulationCompleted event, which seems to be more reliable.

        containerPage.ManipulationStarted += delegate { this.manipulationInProgress = true; };
        containerPage.ManipulationCompleted += delegate
        { 
            this.manipulationInProgress = false;
            PerformDragComplete(); 
        };

Another issue is that DragDelta occasionally reports bad coordinates. So you would need a fix like this:

    Point refPosition = e.GetPosition(null);
    if (refPosition.X == 0 && refPosition.Y == 0)
    {
        Tracer.WriteLine("Skipping buggy event");
        return;
    }

Finally, you can find if list is all the way at the top:

public double VerticalOffset
{
    get
    {
        ViewportControl viewportControl = this.FindChildByName("ViewportControl") as ViewportControl;
        if (viewportControl != null)
        {
            Tracer.WriteLine("ViewPort.Bounds.Top=" + viewportControl.Bounds.Top +  " ViewPort.Top=" + viewportControl.Viewport.Top.ToString() + " State=" + this.ManipulationState);
            return viewportControl.Bounds.Top - viewportControl.Viewport.Top;
        }
        return double.NaN;
    }
}