public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
{
using (
_trace.WriteEventActivity(
TraceProvider.ListViewBaseSource_GetCellStart,
TraceProvider.ListViewBaseSource_GetCellStop
)
)
{
// Marks this item to be materialized, so its actual measured size
// is used during the calculation of the layout.
// This is required for paged lists, so that the layout calculation
// does not eagerly get all the items of the ItemsSource.
UpdateLastMaterializedItem(indexPath);
var index = Owner?.XamlParent?.GetIndexFromIndexPath(IndexPath.FromNSIndexPath(indexPath)) ?? -1;
var identifier = GetReusableCellIdentifier(indexPath);
var listView = (NativeListViewBase)collectionView;
var cell = (ListViewBaseInternalContainer)collectionView.DequeueReusableCell(identifier, indexPath);
using (cell.InterceptSetNeedsLayout())
{
var selectorItem = cell.Content as SelectorItem;
if (selectorItem == null ||
// If it's not a generated container then it must be an item that returned true for IsItemItsOwnContainerOverride (eg an
// explicitly-defined ListViewItem), and shouldn't be recycled for a different item.
!selectorItem.IsGeneratedContainer)
{
cell.Owner = Owner;
selectorItem = Owner?.XamlParent?.GetContainerForIndex(index) as SelectorItem;
cell.Content = selectorItem;
if (this.Log().IsEnabled(Microsoft.Extensions.Logging.LogLevel.Debug))
{
this.Log().Debug($"Creating new view at indexPath={indexPath}.");
}
FrameworkElement.InitializePhaseBinding(selectorItem);
// Ensure the item has a parent, since it's added to the native collection view
// which does not automatically sets the parent DependencyObject.
selectorItem.SetParent(Owner?.XamlParent?.InternalItemsPanelRoot);
}
else if (this.Log().IsEnabled(Microsoft.Extensions.Logging.LogLevel.Debug))
{
this.Log().Debug($"Reusing view at indexPath={indexPath}, previously bound to {selectorItem.DataContext}.");
}
Owner?.XamlParent?.PrepareContainerForIndex(selectorItem, index);
// Normally this happens when the SelectorItem.Content is set, but there's an edge case where after a refresh, a
// container can be dequeued which happens to have had exactly the same DataContext as the new item.
cell.ClearMeasuredSize();
}
Owner?.XamlParent?.TryLoadMoreItems(index);
return(cell);
}
}
