ios7.1.1 UICollectionView Not Reloading Correctly - ios

Question

This is a very strange problem. I have a UICollectionView which seems to run perfectly on the iPad or the simulator as an iPad, but has a problem when running on the iPhone or iPhone simulator. The problem is that if an item is added to the datasource and I perform a reloadData, the freshly added item will not show up in the collection view. If I exit the view controller altogether and reopen it, the item is there. This problem is on the iPhone only, not the iPad, which works perfectly.
In all cases, the number of items returned is correct and the number of passes through the dequeue loop is correct (verified via debugger).
Relevant code below. I initialize the CV in viewDidAppear with the following:
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
flowLayout.minimumInteritemSpacing = 3.0f;
UICollectionViewCell *cvCell = [[UICollectionViewCell alloc] init];
cv = [[UICollectionView alloc] initWithFrame:CGRectMake(1.0f, 80.0f, [Utility screenWidth]-2.0f, [Utility screenHeight]-60.0f) collectionViewLayout:flowLayout];
[cv setDelegate:self];
[cv setDataSource:self];
[cv setAllowsMultipleSelection:NO];
[cv setAllowsSelection:NO];
[cv setBackgroundColor: [UIColor whiteColor]];
[cv registerClass:[cvCell class] forCellWithReuseIdentifier:#"Cell"];
[self.view addSubview:cv];
[self.view sendSubviewToBack:cv];
[self queryData]; // [self queryData] also does a [cv reloadData]
The CV delegate is as follows:
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection: (NSInteger)section
{
return [cvData count];
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"Cell" forIndexPath:indexPath];
[cell.contentView.subviews makeObjectsPerformSelector: #selector(removeFromSuperview)];
Item *item = (Item *) [cvData objectAtIndex:indexPath.row];
CGFloat cellSize = (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) ? 100.0f : 160.0f;
ImageWithAttachedLabel *imageWithLabel = [[ImageWithAttachedLabel alloc] initWithFrame:CGRectMake(0,0,cellSize,cellSize)
withImage: [UIImage imageWithData: item.itemPhoto]
withLabel: item.itemName
roundBottoms: YES];
[cell.contentView addSubview:imageWithLabel];
return cell;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
return 3.0f;
}
Running the debugger finds that numberOfItemsInSection is returns the CORRECT count of the items and the number of passes through the dequeue loop is correct, but the last item added (which should always be the last cell in the cv, as the items are unsorted) is not displayed.
I haven't been able to find any articles mentioning anything quite like this so I'm guessing I have a bug somewhere, but it is elusive.
Any suggestions appreciated.

Answer 1

Perhaps you can force the newly added item to be displayed by doing this after you add the new item to your data source:
int size = [cvData count];
NSIndexPath *lastCell = [NSIndexPath indexPathForRow:size inSection:0];
[self.collectionView insertItemsAtIndexPaths:#[lastCell]];
(assuming you point self.collectionView at your cv)