public static async Task AnimateItems(
this Selector itemsControl,
AnimationDefinition animationDefinition,
double itemDelay = 0.05,
object selectedObject = null,
AnimationDefinition selectedItemAnimationDefinition = null)
{
if (itemsControl == null) return;
if (animationDefinition == null) return;
if (itemDelay <= 0.0)
itemDelay = 0.05;
itemsControl.UpdateLayout();
var animations = new List<Task>();
double baseDelay = animationDefinition.Delay;
for (int index = 0; index < itemsControl.Items.Count; index++)
{
var container = (FrameworkElement)itemsControl.ContainerFromItem(itemsControl.Items[index]);
//var container = (FrameworkElement)itemsControl.ItemContainerGenerator.ContainerFromIndex(index);
if (container == null) continue;
bool found = false;
if (selectedItemAnimationDefinition != null)
{
if ((index == itemsControl.SelectedIndex) ||
((selectedObject != null) && (itemsControl.Items != null) && (selectedObject == itemsControl.Items[index]))
)
{
found = true;
animationDefinition.Delay = baseDelay;
AnimationManager.ClearAnimationProperties(container);
animations.Add(
container.AnimateAsync(selectedItemAnimationDefinition));
}
}
if (!found)
{
animationDefinition.Delay = baseDelay + (itemDelay * index);
AnimationManager.ClearAnimationProperties(container);
animations.Add(
container.AnimateAsync(animationDefinition));
}
}
animationDefinition.Delay = baseDelay;
await Task.WhenAll(animations.ToArray());
}
public async static Task ScrollToItem(this ListViewBase listViewBase, object item)
{
bool isVirtualizing = default(bool);
double previousHorizontalOffset = default(double), previousVerticalOffset = default(double);
// get the ScrollViewer withtin the ListView/GridView
var scrollViewer = listViewBase.GetScrollViewer();
// get the SelectorItem to scroll to
var selectorItem = listViewBase.ContainerFromItem(item) as SelectorItem;
// when it's null, means virtualization is on and the item hasn't been realized yet
if (selectorItem == null)
{
isVirtualizing = true;
previousHorizontalOffset = scrollViewer.HorizontalOffset;
previousVerticalOffset = scrollViewer.VerticalOffset;
// call task-based ScrollIntoViewAsync to realize the item
await listViewBase.ScrollIntoViewAsync(item);
// this time the item shouldn't be null again
selectorItem = (SelectorItem)listViewBase.ContainerFromItem(item);
}
// calculate the position object in order to know how much to scroll to
var transform = selectorItem.TransformToVisual((UIElement)scrollViewer.Content);
var position = transform.TransformPoint(new Point(0, 0));
// when virtualized, scroll back to previous position without animation
if (isVirtualizing)
{
await scrollViewer.ChangeViewAsync(previousHorizontalOffset, previousVerticalOffset, true);
}
// scroll to desired position with animation!
scrollViewer.ChangeView(position.X, position.Y, null);
}
