protected override void ScrollTo(ScrollToRequestEventArgs args)
{
var position = DetermineTargetPosition(args);
if (_carouselViewLoopManager == null)
{
return;
}
//Special case here
//We could have a race condition where we are scrolling our collection to center the first item
//And at the same time the user is requesting we go to a particular item
if (position == -1 && Carousel.Loop)
{
_carouselViewLoopManager.AddPendingScrollTo(args);
return;
}
if (args.IsAnimated)
{
ScrollHelper.AnimateScrollToPosition(position, args.ScrollToPosition);
}
else
{
ScrollHelper.JumpScrollToPosition(position, args.ScrollToPosition);
}
}
void UpdateInitialPosition()
{
int itemCount = 0;
int position;
if (Carousel.CurrentItem != null)
{
var carouselEnumerator = Carousel.ItemsSource.GetEnumerator();
var items = new List <object>();
while (carouselEnumerator.MoveNext())
{
items.Add(carouselEnumerator.Current);
itemCount++;
}
position = items.IndexOf(Carousel.CurrentItem);
Carousel.Position = position;
}
else
{
position = Carousel.Position;
}
_oldPosition = position;
SetCurrentItem(_oldPosition);
var index = Carousel.Loop ? LoopedPosition(itemCount) + _oldPosition : _oldPosition;
ScrollHelper.JumpScrollToPosition(index, Xamarin.Forms.ScrollToPosition.Center);
_gotoPosition = -1;
}
void UpdateInitialPosition()
{
int position = 0;
var items = Carousel.ItemsSource as IList;
var itemCount = items?.Count ?? 0;
if (Carousel.CurrentItem != null || items == null)
{
for (int n = 0; n < itemCount; n++)
{
if (items[n] == Carousel.CurrentItem)
{
position = n;
break;
}
}
Carousel.Position = position;
}
else
{
position = Carousel.Position;
}
_oldPosition = position;
SetCurrentItem(_oldPosition);
var index = Carousel.Loop ? itemCount * 5000 + _oldPosition : _oldPosition;
ScrollHelper.JumpScrollToPosition(index, Xamarin.Forms.ScrollToPosition.Center);
}
internal void AdjustScrollForItemUpdate()
{
if (ItemsView.ItemsUpdatingScrollMode == ItemsUpdatingScrollMode.KeepLastItemInView)
{
ScrollTo(new ScrollToRequestEventArgs(ItemsViewAdapter.ItemCount, 0,
Xamarin.Forms.ScrollToPosition.MakeVisible, true));
}
else if (ItemsView.ItemsUpdatingScrollMode == ItemsUpdatingScrollMode.KeepScrollOffset)
{
ScrollHelper.UndoNextScrollAdjustment();
}
}
protected virtual void ScrollTo(ScrollToRequestEventArgs args)
{
var position = DetermineTargetPosition(args);
if (args.IsAnimated)
{
ScrollHelper.AnimateScrollToPosition(position, args.ScrollToPosition);
}
else
{
ScrollHelper.JumpScrollToPosition(position, args.ScrollToPosition);
}
}
