UICollectionView cellForItemAtIndexPath not called fix,UICollectionView margin fix

cellForItemAtIndexPath not called for many reasons

for my problem: cell is not in the visible area of UICollectionView, because the Adjust scroll view insets option of parent view controller is on by default, this cause automatic add margin to the UICollectionView

fix

toggle off Adjust Scroll View Insets option in parent view controller attribute inspector or add this code to parent view controller viewDidLoad method:

self.automaticallyAdjustsScrollViewInsets = NO;