/// <summary>
/// Enumerates all the items that are currently visible in an ItemsControl. This
/// implementation works for both virtualized and non-virtualized panels.
/// </summary>
public static IEnumerable <FrameworkElement> GetItemsInView(this ItemsControl itemsControl)
{
// find the panel that hosts our items - this is 'cached'
// using the ItemsControl.Tag property to minimize visual tree
// navigation
Panel itemsHostPanel = itemsControl.Tag as Panel;
if (itemsHostPanel == null)
{
itemsHostPanel = itemsControl.Descendants <Panel>()
.Cast <Panel>()
.Where(p => p.IsItemsHost)
.SingleOrDefault();
itemsControl.Tag = itemsHostPanel;
}
VirtualizingStackPanel vsp = itemsHostPanel as VirtualizingStackPanel;
if (vsp != null)
{
// implementation for virtualizing lists
return(GetItemsInView(itemsControl, vsp));
}
else
{
// implementation for non-virtualizing lists
return(Enumerable.Range(0, itemsControl.Items.Count)
.Select(index => itemsControl.ItemContainerGenerator.ContainerFromIndex(index))
.Cast <FrameworkElement>()
.Where(container => container.GetRelativePosition(itemsControl).Y + container.ActualHeight > 0)
.Where(container => container.GetRelativePosition(itemsControl).Y - container.ActualHeight < itemsControl.ActualHeight));
}
}
public CatalogPage()
{
InitializeComponent();
Loaded += (sender, e) =>
{
ViewModel.CatalogNavigated += ViewModelOnCatalogNavigated;
ViewModel.PropertyChanged += ViewModelOnPropertyChanged;
var isSearchEnabled = ViewModel.IsSearchEnabled;
AppBar.Buttons[0].IsVisible = isSearchEnabled;
AppBar.MenuItems[0].IsVisible = ViewModel.CanRefresh;
AppBar.Mode = isSearchEnabled ? ApplicationBarMode.Default : ApplicationBarMode.Minimized;
ItemsControl.Margin = isSearchEnabled ? new Thickness(24, 48, 24, 72) : new Thickness(24, 48, 24, 24);
_scrollViewer = ItemsControl.Descendants <ScrollViewer>().SingleOrDefault();
};
Unloaded += (sender, e) =>
{
ViewModel.CatalogNavigated -= ViewModelOnCatalogNavigated;
ViewModel.PropertyChanged -= ViewModelOnPropertyChanged;
};
}
private void LocateScrollViewer()
{
_scrollViewer = _todoList.Descendants <ScrollViewer>()
.Cast <ScrollViewer>()
.Single();
// allow interactions to perform some action when the ScrollViewer has been located
// such as add event handlers
ScrollViewerLocated(_scrollViewer);
}
public static IEnumerable <FrameworkElement> GetItemsInView(this ItemsControl itemsControl)
{
VirtualizingStackPanel virtualizingStackPanel = itemsControl.Descendants <VirtualizingStackPanel>().First <DependencyObject>() as VirtualizingStackPanel;
int firstVisibleItem = (int)virtualizingStackPanel.VerticalOffset;
int visibleItemCount = (int)virtualizingStackPanel.ViewportHeight;
for (int index = firstVisibleItem; index <= firstVisibleItem + visibleItemCount + 1; ++index)
{
FrameworkElement frameworkElement = itemsControl.ItemContainerGenerator.ContainerFromIndex(index) as FrameworkElement;
if (frameworkElement != null)
{
yield return(frameworkElement);
}
}
}
/// <summary>
/// Enumerates all the items that are currently visible in am ItemsControl. This implementation assumes
/// that a VirtualizingStackPanel is being used as the ItemsPanel.
/// </summary>
public static IEnumerable <FrameworkElement> GetItemsInView(this ItemsControl itemsControl)
{
// locate the stack panel that hosts the items
VirtualizingStackPanel vsp = itemsControl.Descendants <VirtualizingStackPanel>().First() as VirtualizingStackPanel;
// iterate over each of the items in view
int firstVisibleItem = (int)vsp.VerticalOffset;
int visibleItemCount = (int)vsp.ViewportHeight;
for (int index = firstVisibleItem; index <= firstVisibleItem + visibleItemCount + 1; index++)
{
var item = itemsControl.ItemContainerGenerator.ContainerFromIndex(index) as FrameworkElement;
if (item == null)
{
continue;
}
yield return(item);
}
}
public static IEnumerable <FrameworkElement> GetItemsInView(this ItemsControl itemsControl)
{
var itemsHostPanel = itemsControl.Tag as Panel;
if (itemsHostPanel == null)
{
itemsHostPanel = itemsControl.Descendants <Panel>().Cast <Panel>().FirstOrDefault(p => p.IsItemsHost);
itemsControl.Tag = itemsHostPanel;
}
var vsp = itemsHostPanel as VirtualizingStackPanel;
if (vsp != null)
{
return(GetItemsInView(itemsControl, vsp));
}
return(Enumerable.Range(0, itemsControl.Items.Count)
.Select(index => itemsControl.ItemContainerGenerator.ContainerFromIndex(index))
.Cast <FrameworkElement>()
.Where(c => c.GetRelativePositionIn(itemsControl).Y + c.ActualHeight > 0)
.Where(c => c.GetRelativePositionIn(itemsControl).Y - c.ActualHeight <
itemsControl.ActualHeight));
}
private static void OnIsPivotAnimatedChanged(DependencyObject d, DependencyPropertyChangedEventArgs args)
{
ItemsControl list = d as ItemsControl;
list.Loaded += (s2, e2) =>
{
// locate the pivot control that this list is within
Pivot pivot = list.Ancestors <Pivot>().Single() as Pivot;
// and its index within the pivot
int pivotIndex = pivot.Items.IndexOf(list.Ancestors <PivotItem>().Single());
bool selectionChanged = false;
pivot.SelectionChanged += (s3, e3) =>
{
selectionChanged = true;
};
// handle manipulation events which occur when the user
// moves between pivot items
pivot.ManipulationCompleted += (s, e) =>
{
if (!selectionChanged)
{
return;
}
selectionChanged = false;
if (pivotIndex != pivot.SelectedIndex)
{
return;
}
// determine which direction this tab will be scrolling in from
bool fromRight = e.TotalManipulation.Translation.X <= 0;
// locate the stack panel that hosts the items
VirtualizingStackPanel vsp = list.Descendants <VirtualizingStackPanel>().First() as VirtualizingStackPanel;
// iterate over each of the items in view
int firstVisibleItem = (int)vsp.VerticalOffset;
int visibleItemCount = (int)vsp.ViewportHeight;
for (int index = firstVisibleItem; index <= firstVisibleItem + visibleItemCount; index++)
{
// find all the item that have the AnimationLevel attached property set
var lbi = list.ItemContainerGenerator.ContainerFromIndex(index);
if (lbi == null)
{
continue;
}
vsp.Dispatcher.BeginInvoke(() =>
{
var animationTargets = lbi.Descendants().Where(p => ListAnimation.GetAnimationLevel(p) > -1);
foreach (FrameworkElement target in animationTargets)
{
// trigger the required animation
GetAnimation(target, fromRight).Begin();
}
});
}
;
};
};
}
