UICollectionView: UICollectionViewCell object is always null in sizeForItemAtIndexPath

Question

I have a collection view that contains different custom cells.

These cells contain different content that varies in size.

The cells are defined in the Storyboard, so no registering needed in code.

All i want to do now is change the size in the delegate method depending on the content:

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {

id cellAtIndexPath = [collectionView cellForItemAtIndexPath:indexPath];

NSLog(@"The cell: %@", cellAtIndexPath);

...
e.g. calling sizeToFit methods and cumulating the sizes of the cells' subviews
...

}

The Method is called as expected for every cell, but cellAtIndexPath always returns NULL, no matter what i tried. So i am not able to access the cell object at the indexPath or its content view.

Any suggestions why i cannot access the cell object?

Answer 1

The collectionView:layout:sizeForItemAtIndexPath method is called by the collection view's flow layout object. The layout is asking for the size of a cell at a time before the cells are added to the collection view. You will have to compute the desired cell size "on your own" and return it.