ListBox offset in WP7

问题:

It is possible set the offset for a ListBox? All that I can find is scroll to an element, but I need to scroll the ListBox to any position.

As an alternative, there are any other component that can make virtualize their items, and that I can control the offset?

回答1:

You can get the ListBox's ScrollViewer and use its ScrollToVerticalOffset-method. To get the ScrollViewer, you can for example hook up to the ListBox's Loaded-event like the following:

XAML:

<ListBox Loaded="HookScrollViewer">

Code-behind:

    private void HookScrollViewer(object sender, RoutedEventArgs e)
    {
        var element = (FrameworkElement)sender;
        var scrollViewer = ControlHelpers.FindChildOfType<ScrollViewer>(element);

        if (scrollViewer == null)
            return;

        this.myScrollViewer = scrollViewer;
    }

The ControlHerlpers.FindChildOfType-method is implement this way:

    public static T FindChildOfType<T>(DependencyObject root) where T : class
    {
        var queue = new Queue<DependencyObject>();
        queue.Enqueue(root);

        while (queue.Count > 0)
        {
            var current = queue.Dequeue();
            for (int i = VisualTreeHelper.GetChildrenCount(current) - 1; 0 <= i; i--)
            {
                var child = VisualTreeHelper.GetChild(current, i);
                var typedChild = child as T;
                if (typedChild != null)
                {
                    return typedChild;
                }
                queue.Enqueue(child);
            }
        }
        return null;
    }

Now you have the ListBox's ScrollViewer in the myScrollViewer member and you can directly access its methods. For example, to scroll bottom you can call:

this.myScrollViewer.ScrollToVerticalOffset(double.MaxValue);