Animer (en douceur) ScrollViewer programmatically

y a-t-il un moyen d'animer en douceur un décalage vertical de ScrollViewer dans Windows Phone 8.1 Runtime?

j'ai essayé d'utiliser la méthode ScrollViewer.ChangeView() et le changement de décalage vertical n'est pas animé peu importe si je mets le paramètre disableAnimation à vrai ou faux.

par exemple: myScrollViewer.ChangeView(null, myScrollViewer.VerticalOffset + p, null, false); L'offset est modifié sans animation.

j'ai aussi essayé d'utiliser un médiateur de décalage vertical:

/// <summary>
/// Mediator that forwards Offset property changes on to a ScrollViewer
/// instance to enable the animation of Horizontal/VerticalOffset.
/// </summary>
public sealed class ScrollViewerOffsetMediator : FrameworkElement
{
    /// <summary>
    /// ScrollViewer instance to forward Offset changes on to.
    /// </summary>
    public ScrollViewer ScrollViewer
    {
        get { return (ScrollViewer)GetValue(ScrollViewerProperty); }
        set { SetValue(ScrollViewerProperty, value); }
    }
    public static readonly DependencyProperty ScrollViewerProperty =
            DependencyProperty.Register("ScrollViewer",
            typeof(ScrollViewer),
            typeof(ScrollViewerOffsetMediator),
            new PropertyMetadata(null, OnScrollViewerChanged));
    private static void OnScrollViewerChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
    {
        var mediator = (ScrollViewerOffsetMediator)o;
        var scrollViewer = (ScrollViewer)(e.NewValue);
        if (null != scrollViewer)
        {
            scrollViewer.ScrollToVerticalOffset(mediator.VerticalOffset);
        }
    }

    /// <summary>
    /// VerticalOffset property to forward to the ScrollViewer.
    /// </summary>
    public double VerticalOffset
    {
        get { return (double)GetValue(VerticalOffsetProperty); }
        set { SetValue(VerticalOffsetProperty, value); }
    }
    public static readonly DependencyProperty VerticalOffsetProperty =
            DependencyProperty.Register("VerticalOffset",
            typeof(double),
            typeof(ScrollViewerOffsetMediator),
            new PropertyMetadata(0.0, OnVerticalOffsetChanged));
    public static void OnVerticalOffsetChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
    {
        var mediator = (ScrollViewerOffsetMediator)o;
        if (null != mediator.ScrollViewer)
        {
            mediator.ScrollViewer.ScrollToVerticalOffset((double)(e.NewValue));
        }
    }

    /// <summary>
    /// Multiplier for ScrollableHeight property to forward to the ScrollViewer.
    /// </summary>
    /// <remarks>
    /// 0.0 means "scrolled to top"; 1.0 means "scrolled to bottom".
    /// </remarks>
    public double ScrollableHeightMultiplier
    {
        get { return (double)GetValue(ScrollableHeightMultiplierProperty); }
        set { SetValue(ScrollableHeightMultiplierProperty, value); }
    }
    public static readonly DependencyProperty ScrollableHeightMultiplierProperty =
            DependencyProperty.Register("ScrollableHeightMultiplier",
            typeof(double),
            typeof(ScrollViewerOffsetMediator),
            new PropertyMetadata(0.0, OnScrollableHeightMultiplierChanged));
    public static void OnScrollableHeightMultiplierChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
    {
        var mediator = (ScrollViewerOffsetMediator)o;
        var scrollViewer = mediator.ScrollViewer;
        if (null != scrollViewer)
        {
            scrollViewer.ScrollToVerticalOffset((double)(e.NewValue) * scrollViewer.ScrollableHeight);
        }
    }
}

et je peux animer la propriété VerticalOffset avec DoubleAnimation :

Storyboard sb = new Storyboard();
DoubleAnimation da = new DoubleAnimation();
da.EnableDependentAnimation = true;
da.From = Mediator.ScrollViewer.VerticalOffset;
da.To = da.From + p;
da.Duration = new Duration(TimeSpan.FromMilliseconds(300));
da.EasingFunction = new ExponentialEase() { EasingMode = EasingMode.EaseOut };
Storyboard.SetTarget(da, Mediator);
Storyboard.SetTargetProperty(da, "(Mediator.VerticalOffset)");
sb.Children.Add(da);

sb.Begin();

médiateur est déclaré dans XAML. Mais cette animation n'est pas fluide sur mon appareil (Lumia 930).