UICollectionView sorts cells automatically UICollectionViewFlowLayout

I am currently working on automating cells that are new in iOS8

.

According to the WWDC 2014 video "What's New in the table and a collection of" all that is required for the automatic sorting of cells - it is set estimatedSize

in the UICollectionViewFlowLayout

specified in the initialization UICollectionView

, and override sizeThatFits:

in UICollectionViewCell

.

Initialization

UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];

[flowLayout setEstimatedItemSize:CGSizeMake(146.0f, 156.0f)];

_collectionView = [[UICollectionView alloc] initWithFrame:[_containerView bounds] collectionViewLayout:flowLayout];

      

        
        
        
      

    

sizeThatFits

in my cell where _userLabel is the label that sits at the bottom and marks the actual height.

- (CGSize)sizeThatFits:(CGSize)size
{
    CGSize actualSize = CGSizeMake([[self contentView] bounds].size.width, [_userLabel frame].origin.x + [_userLabel bounds].size.height);

    return actualSize;
}

      

        
        
        
      

    

It turns out that the actual size has a greater height than my calculated size, which should be fine, and the cell actually resizes in height correctly.

Now with iPhone6 ​​and 6+, the width may differ as well. I want the cells to display the screen width correctly. So I have applied three delegate methods in UICollectionViewFlowLayout; my first intuition is to calculate the width that I want the cells to have screen width, section inserts and paragraph spacing.

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UIEdgeInsets sectionInsets = [self collectionView:collectionView layout:collectionViewLayout insetForSectionAtIndex:[indexPath section]];
    CGFloat interItemSpacing = [(UICollectionViewFlowLayout *) collectionViewLayout minimumInteritemSpacing];

    CGFloat cellWidth = ([_collectionView bounds].size.width - sectionInsets.left - sectionInsets.right - interItemSpacing) / 2;

    CGSize collectionViewCellSize = CGSizeMake(cellWidth, 156.0f);

    return collectionViewCellSize;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 12.0f;
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{   
    return UIEdgeInsetsMake(10.0f, 10.0f, 10.0f, 10.0f);
}

      

        
        
        
      

    

It works, however, in part. The CollectionView will not respect insertion of the top section, and when scrolling through the CollectionView, selecting another tab and then back again, the cells seem to have disappeared.

Apparently I am doing something wrong, but I cannot figure out where. Anyone got it?