internal bool IsOnCurrentPage(ListBoxItem item)
        {
            var itemsHostRect = Rect.Empty;
            var listBoxItemRect = Rect.Empty;

            if (_visual == null)
            {
                ItemsControlHelper ich = new ItemsControlHelper(ListBox);
                ScrollContentPresenter scp = ich.ScrollHost == null ? null : ich.ScrollHost.GetVisualDescendants().OfType<ScrollContentPresenter>().FirstOrDefault();
                _visual = (ich.ScrollHost == null) ? null : ((scp == null) ? ((FrameworkElement)ich.ScrollHost) : ((FrameworkElement)scp));
            }

            if (_visual == null)
                return true;

            itemsHostRect = new Rect(0.0, 0.0, _visual.ActualWidth, _visual.ActualHeight);
            //ListBoxItem item = ListBox.ItemContainerGenerator.ContainerFromIndex(index) as ListBoxItem;
            if (item == null)
            {
                listBoxItemRect = Rect.Empty;
                return false;
            }

            GeneralTransform transform = item.TransformToVisual(_visual);
            listBoxItemRect = new Rect(transform.Transform(new Point()), transform.Transform(new Point(item.ActualWidth, item.ActualHeight)));
            if (!this.IsVerticalOrientation())
            {
                return ((itemsHostRect.Left <= listBoxItemRect.Left) && (listBoxItemRect.Right <= itemsHostRect.Right));
            }

            return ((listBoxItemRect.Bottom + 100 >= itemsHostRect.Top) && (listBoxItemRect.Top - 100 <= itemsHostRect.Bottom));
            //return ((itemsHostRect.Top <= listBoxItemRect.Bottom) && (listBoxItemRect.Top <= itemsHostRect.Bottom));
        }
Exemplo n.º 2
0
        /// <summary>
        /// Indicate whether the specified item is currently visible.
        /// </summary>
        /// <param name="item">The item.</param>
        /// <param name="itemsHostRect">Rect for the item host element.</param>
        /// <param name="listBoxItemRect">Rect for the ListBoxItem element.</param>
        /// <returns>True if the item is visible; false otherwise.</returns>
        /// <remarks>Similar to WPF's corresponding ItemsControl method.</remarks>
        private bool IsOnCurrentPage(object item, out Rect itemsHostRect, out Rect listBoxItemRect)
        {
            // Get Rect for item host element
            DependencyObject ItemsHost = VisualTreeHelper.GetChild(this, 0);

            ItemsHost = VisualTreeHelper.GetChild(ItemsHost, 0);
            FrameworkElement itemsHost =
                (null != TemplateScrollViewer) ?
                ((null != TemplateScrollViewer.ElementScrollContentPresenter) ? TemplateScrollViewer.ElementScrollContentPresenter as FrameworkElement : TemplateScrollViewer as FrameworkElement) :
                ItemsHost as FrameworkElement;

            if (itemsHost == null)
            {
                itemsHostRect   = Rect.Empty;
                listBoxItemRect = Rect.Empty;
                return(false);
            }
            itemsHostRect = new Rect(new Point(), new Point(itemsHost.RenderSize.Width, itemsHost.RenderSize.Height));

            ListBoxItem listBoxItem = (ListBoxItem)ItemContainerGenerator.ContainerFromItem(item);

            if (listBoxItem == null)
            {
                listBoxItemRect = Rect.Empty;
                return(false);
            }

            listBoxItemRect = new Rect(new Point(), listBoxItem.RenderSize);

            // Adjust Rect to account for padding
            Control itemsHostControl = itemsHost as Control;

            if (null != itemsHostControl)
            {
                Thickness padding = itemsHostControl.Padding;
                itemsHostRect = new Rect(
                    itemsHostRect.Left + padding.Left,
                    itemsHostRect.Top + padding.Top,
                    itemsHostRect.Width - padding.Left - padding.Right,
                    itemsHostRect.Height - padding.Top - padding.Bottom);
            }
            // Get relative Rect for ListBoxItem
            GeneralTransform generalTransform = listBoxItem.TransformToVisual(itemsHost);

            if (generalTransform != null)
            {
                listBoxItemRect = new Rect(generalTransform.Transform(new Point()), generalTransform.Transform(new Point(listBoxItem.RenderSize.Width, listBoxItem.RenderSize.Height)));
            }

            // Return result
            return(IsVerticalOrientation() ?
                   (itemsHostRect.Top <= listBoxItemRect.Top) && (listBoxItemRect.Bottom <= itemsHostRect.Bottom) :
                   (itemsHostRect.Left <= listBoxItemRect.Left) && (listBoxItemRect.Right <= itemsHostRect.Right));
        }