/// <summary>
/// Retrieves the visible containers in a LongListSelector and adds them to <paramref name="items"/>.
/// </summary>
/// <param name="list">LongListSelector that contains the items.</param>
/// <param name="itemsPanel">Direct parent of the items.</param>
/// <param name="items">List to populate with the containers currently in the viewport</param>
/// <param name="selectContent">
/// Specifies whether to return the container or its content.
/// For headers, we can't apply projections on the container directly (or everything will go blank),
/// so we will apply them on the content instead.
/// </param>
private static void AddVisibileContainers(LongListSelector list, Canvas itemsPanel, List <KeyValuePair <double, FrameworkElement> > items, bool selectContent)
{
foreach (DependencyObject obj in VisualTreeExtensions.GetVisualChildren(itemsPanel))
{
ContentPresenter container = obj as ContentPresenter;
if (container != null &&
(!selectContent ||
(VisualTreeHelper.GetChildrenCount(container) == 1 &&
VisualTreeHelper.GetChild(container, 0) is FrameworkElement)))
{
GeneralTransform itemTransform = null;
try
{
itemTransform = container.TransformToVisual(list);
}
catch (ArgumentException)
{
// Ignore failures when not in the visual tree
break;
}
Rect boundingBox = new Rect(itemTransform.Transform(new Point()), itemTransform.Transform(new Point(container.ActualWidth, container.ActualHeight)));
if (boundingBox.Bottom > 0 && boundingBox.Top < list.ActualHeight)
{
items.Add(
new KeyValuePair <double, FrameworkElement>(
boundingBox.Top,
selectContent
? (FrameworkElement)VisualTreeHelper.GetChild(container, 0)
: container));
}
}
}
}
/// <summary>
/// Method that takes care of setting the two way bindings for all the attached properties
/// from MapOverlay to the actual UI (not the intermediary presenter).
/// </summary>
/// <remarks>
/// Even though the MapOverlay is supposed to be the target, it is the source due to issues with
/// setting a two way binding where the source is an attached property
/// </remarks>
/// <param name="mapOverlay">MapOverlay that will be used in the two way binding</param>
internal static void BindMapOverlayProperties(MapOverlay mapOverlay)
{
MapOverlayItem mapOverlayItem;
DependencyObject targetObject;
mapOverlayItem = (MapOverlayItem)mapOverlay.Content;
targetObject = VisualTreeExtensions.GetVisualChildren(mapOverlayItem).FirstOrDefault();
if (targetObject == null)
{
throw new InvalidOperationException("Could not bind the properties because there was no UI");
}
BindMapOverlayProperties(mapOverlay, targetObject);
}
/// <summary>
/// Clear the bindings created when the overlay was created by MapChild
/// </summary>
/// <param name="mapOverlay">MapOverlay that was created by MapChild</param>
internal static void ClearMapOverlayBindings(MapOverlay mapOverlay)
{
MapOverlayItem mapOverlayItem;
DependencyObject targetObject;
mapOverlayItem = (MapOverlayItem)mapOverlay.Content;
targetObject = VisualTreeExtensions.GetVisualChildren(mapOverlayItem).FirstOrDefault();
// In some cases, the MapOverlay was not presented in the UI.
// Bindings are create when the MapOverlay is presented in the, so
// if there is no visual, there is nothing to clear.
if (targetObject != null)
{
ClearMapOverlayBindings(mapOverlay, targetObject);
}
}