As far as I can see, UICollectionViewFlowLayout justifies all the lines of a section except the last one. So for example, if there aren\'t enough items to fill
You can do this by subclassing UICollectionViewFlowLayout and overriding layoutAttributesForElementsInRect: and layoutAttributesForItemAtIndexPath: to place all the items in the last line (except the first, which is already correct) where you want them, by changing the frame property of the item's UICollectionViewLayoutAttributes object.