UITableViewSource never creates cells - ios

Question

I am writing a Xamarin.iOS application with MvvmCross. I am trying to make a table, I can see the items being binded into the source, but I never see any cells being created. The function GetOrCreateCellFor never gets called. Here is my code:
public class ContactsManager
{
ContactsView _contactsView;
public ContactsManager()
{
_contactsView = new ContactsView();
Source = new FriendTableViewSource(_contactsView.FriendsTableView);
_contactsView.FriendsTableView.Source = Source;
}
public FriendTableViewSource Source { get; set; }
}
public class FriendTableViewSource : MvxTableViewSource
{
private readonly List<SeeMyFriendsItemViewModel> _content = new List<SeeMyFriendsItemViewModel>();
private readonly UITableView _tableView;
public FriendTableViewSource(UITableView t) : base(t)
{
_tableView = t;
t.RegisterNibForCellReuse(UINib.FromName(FriendCell.Key, NSBundle.MainBundle), FriendCell.Key);
}
private void Init(IEnumerable<SeeMyFriendsItemViewModel> items)
{
_content.Clear();
_content.AddRange(items);
}
public override System.Collections.IEnumerable ItemsSource
{
get
{
return base.ItemsSource;
}
set
{
// I put a break point here to check if I'm getting the items, and it is, so the binding is fine...
if (value != null)
Init(value.Cast<SeeMyFriendsItemViewModel>());
base.ItemsSource = value;
_tableView.ReloadData();
}
}
public override nfloat GetHeightForRow(UITableView tableView, NSIndexPath indexPath)
{
return 60;
}
protected override UITableViewCell GetOrCreateCellFor(UITableView tableView, NSIndexPath indexPath, object item)
{
// This function never gets called!
return TableView.DequeueReusableCell(FriendCell.Key, indexPath);
}
}
[Register("FriendCell")]
public class FriendCell : MvxTableViewCell
{
public static readonly NSString Key = new NSString("FriendCell");
public static readonly UINib Nib;
static FriendCell()
{
Nib = UINib.FromName("FriendCell", NSBundle.MainBundle);
}
protected FriendCell(IntPtr handle) : base(handle)
{
BackgroundColor = UIColor.Red;
}
}
EDIT
This is what a working version of your source should look like. What's also interesting is that GetOrCreateCellFor won't get called if the table is not added to your view.
public class FriendTableViewSource : MvxTableViewSource
{
private readonly List<SeeMyFriendsItemViewModel> _content = new List<SeeMyFriendsItemViewModel>();
private MvxNotifyCollectionChangedEventSubscription _subscription;
public FriendTableViewSource(UITableView t) : base(t)
{
t.RegisterClassForCellReuse(typeof(FriendCell), FriendCell.Key);
}
private void Init(IEnumerable<SeeMyFriendsItemViewModel> items)
{
_content.Clear();
_content.AddRange(items);
}
public override System.Collections.IEnumerable ItemsSource
{
get
{
return base.ItemsSource;
}
set
{
if (value != null)
{
Init(value.Cast<SeeMyFriendsItemViewModel>());
var collectionChanged = value as System.Collections.Specialized.INotifyCollectionChanged;
if (collectionChanged != null)
{
_subscription = collectionChanged.WeakSubscribe(CollectionChangedOnCollectionChanged);
}
}
base.ItemsSource = value;
ReloadTableData();
}
}
protected override void CollectionChangedOnCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs args)
{
if (args.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
{
foreach (var item in args.NewItems)
{
var chatItem = item as SeeMyFriendsItemViewModel;
_content.Add(chatItem);
}
}
Init(ItemsSource.Cast<SeeMyFriendsItemViewModel>());
base.CollectionChangedOnCollectionChanged(sender, args);
InvokeOnMainThread(() => {
ReloadTableData();
TableView.SetContentOffset(new CGPoint(0, TableView.ContentSize.Height - TableView.Frame.Size.Height), true);
});
}
public override nfloat GetHeightForRow(UITableView tableView, NSIndexPath indexPath)
{
return 60;
}
public override nint RowsInSection(UITableView tableview, nint section)
{
return _content.Count();
}
public override nint NumberOfSections(UITableView tableView)
{
return 1;
}
protected override object GetItemAt(NSIndexPath indexPath)
{
if (indexPath.Row < _content.Count)
return _content[indexPath.Row];
return null;
}
protected override UITableViewCell GetOrCreateCellFor(UITableView tableView, NSIndexPath indexPath, object item)
{
return TableView.DequeueReusableCell(FriendCell.Key, indexPath);
}
}

Answer 1

Override RowsInSection in FriendTableViewSource .
Since tableview needs row count and row height to decide its frame, if height = 0 or count = 0, GetOrCreateCellFor will never be called.