internal void OnItemsSourceChanging(IEnumerable oldValue, IEnumerable newValue)
{
// wrap up enumerable, IList, IList<T>, and IReadOnlyList<T>
var itemSourceAsList = newValue?.ToReadOnlyList();
// allow interception of itemSource
var onCollectionChanged = _onCollectionChanged;
itemSourceAsList = OnItemsSourceChanging(itemSourceAsList, ref onCollectionChanged);
if (itemSourceAsList == null)
{
throw new InvalidOperationException(
"OnItemsSourceChanging must return non-null itemSource as IReadOnlyList");
}
// keep callback alive
_onCollectionChangedProxy = onCollectionChanged;
// dispatch CollectionChangedEvent to ItemView without a strong reference to ItemView and
// synchronize dispatch and element access via CollectionSynchronizationContext protocol
_itemSourceProxy?.Dispose();
_itemSourceProxy = new ItemsSourceProxy(
itemsSource: newValue,
itemsSourceAsList: itemSourceAsList,
onCollectionChanged: new WeakReference <NotifyCollectionChangedEventHandler>(_onCollectionChangedProxy)
);
OnItemsSourceChanged(oldValue, newValue);
}
private void ItemsSource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
foreach (ListElement item in e.NewItems)
{
var add = true;
foreach (var i in ItemsSourceProxy)
{
if (!string.IsNullOrEmpty(i.Id) && i.Id == item.Id)
{
i.ActionType = item.ActionType;
i.Description = item.Description;
i.DescriptionFontSize = item.DescriptionFontSize;
i.DescriptionTextColor = item.DescriptionTextColor;
i.FontSize = item.FontSize;
i.Image = item.Image;
i.Resource = item.Resource;
i.TextColor = item.TextColor;
i.Title = item.Title;
add = false;
break;
}
}
if (add)
{
ItemsSourceProxy.Add(item);
}
}
}
}
public void Draw( )
{
foreach (ListElement item in ItemsSource)
{
var add = true;
foreach (var i in ItemsSourceProxy)
{
if (!string.IsNullOrEmpty(i.Id) && i.Id == item.Id)
{
i.ActionType = item.ActionType;
i.Description = item.Description;
i.DescriptionFontSize = item.DescriptionFontSize;
i.DescriptionTextColor = item.DescriptionTextColor;
i.FontSize = item.FontSize;
i.Image = item.Image;
i.Resource = item.Resource;
i.TextColor = item.TextColor;
i.Title = item.Title;
add = false;
break;
}
}
if (add)
{
ItemsSourceProxy.Add(item);
}
}
}
public ItemView()
{
_onCollectionChanged = _onCollectionChangedProxy = OnCollectionChanged;
_itemSourceProxy = new ItemsSourceProxy(
itemsSource: Enumerable.Empty <object>(),
itemsSourceAsList: OnInitializeItemSource(),
onCollectionChanged: new WeakReference <NotifyCollectionChangedEventHandler>(_onCollectionChangedProxy)
);
}
