FlowListView not fully updating UI when changing ObservableCollection<T> - mvvm

Question

When I remove objects from the list the UI doesn't reflect the current state of the list, normally failling by only one item.
Example: If I remove 4 items, on the UI only shows that I removed 3 items
private ObservableCollection<Card> _cards;
public ObservableCollection<Card> Cards
{
get
{
if (_cards == null)
{
_cards = new ObservableCollection<Card>();
return _cards;
}
return _cards;
}
set
{
SetValue(ref _cards, value);
}
}
My remove method
private void RemoveFromCards(Card card)
{
for (int i = Cards.Count - 1; i >= 0; i--)
{
if (Cards[i].Id == card.Id)
{
Cards.RemoveAt(i);
/* I tried this but doesn't work also
*
*
ObservableCollection<Card> copy = Cards;
copy.RemoveAt(i);
Cards = copy;
*/
}
}
}
Calling remove method
private void RemoveCardsFromView(List<Archive> cards)
{
foreach (Archive a in cards)
{
Card c = new Card {Id = a.CardId};
RemoveFromCards(c);
}
}
Calling code
public async Task RefreshCardsView()
{
if (!CrossConnectivity.Current.IsConnected)
{
BuildToast(false,"No internet connection");
return;
}
try
{
JsonResult cards = (JsonResult) await HttpMiddleman.GetCards();
RemoveCardsFromView(cards.Data.DeletedCards);
AddCardsToView(cards.Data.AddedCards);
}
catch (Exception e)
{
Debug.WriteLine(e.Message);
BuildToast(false,"Could not refresh");
}
}
My binding in FlowListView
<controls:FlowListView x:Name="Board" HasUnevenRows="True"
BackgroundColor="Black"
FlowColumnCount="2"
FlowItemTappedCommand="{Binding ExecuteActionCommand}"
FlowColumnMinWidth="110"
IsPullToRefreshEnabled="True"
IsRefreshing="{Binding IsRefreshing}"
RefreshCommand="{Binding RefreshViewCommand}"
FlowItemsSource="{Binding Cards}"> .....
Thanks in advance guys

Answer 1

make sure that you fire correctly OnPropertyChanged after SetValue() in property statement
and
try with this class (from xamarin) and pass ienumerable of card instead card only object.
Example
private void RemoveFromCards(Card card)
{
Cards.RemoveRange(new []{card});
}
//or directly from
private void RemoveCardsFromView(List<Archive> cards)
{
Cards.RemoveRange(cards.Select(s=> new Card {Id = a.CardId}));
}
/// <summary>
/// Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed.
/// </summary>
/// <typeparam name="T"></typeparam>
public class ObservableRangeCollection<T> : ObservableCollection<T>
{
/// <summary>
/// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class.
/// </summary>
public ObservableRangeCollection()
: base()
{
}
/// <summary>
/// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class that contains elements copied from the specified collection.
/// </summary>
/// <param name="collection">collection: The collection from which the elements are copied.</param>
/// <exception cref="System.ArgumentNullException">The collection parameter cannot be null.</exception>
public ObservableRangeCollection(IEnumerable<T> collection)
: base(collection)
{
}
/// <summary>
/// Adds the elements of the specified collection to the end of the ObservableCollection(Of T).
/// </summary>
public void AddRange(IEnumerable<T> collection, NotifyCollectionChangedAction notificationMode = NotifyCollectionChangedAction.Add)
{
if (collection == null)
throw new ArgumentNullException("collection");
CheckReentrancy();
if (notificationMode == NotifyCollectionChangedAction.Reset)
{
foreach (var i in collection)
{
Items.Add(i);
}
OnPropertyChanged(new PropertyChangedEventArgs("Count"));
OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
return;
}
int startIndex = Count;
var changedItems = collection is List<T> ? (List<T>)collection : new List<T>(collection);
foreach (var i in changedItems)
{
Items.Add(i);
}
OnPropertyChanged(new PropertyChangedEventArgs("Count"));
OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, changedItems, startIndex));
}
/// <summary>
/// Removes the first occurence of each item in the specified collection from ObservableCollection(Of T).
/// </summary>
public void RemoveRange(IEnumerable<T> collection)
{
if (collection == null)
throw new ArgumentNullException("collection");
foreach (var i in collection)
Items.Remove(i);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
/// <summary>
/// Clears the current collection and replaces it with the specified item.
/// </summary>
public void Replace(T item)
{
ReplaceRange(new T[] { item });
}
/// <summary>
/// Clears the current collection and replaces it with the specified collection.
/// </summary>
public void ReplaceRange(IEnumerable<T> collection)
{
if (collection == null)
throw new ArgumentNullException("collection");
Items.Clear();
AddRange(collection, NotifyCollectionChangedAction.Reset);
}
}