UICollectionView Self Sizing Cells with Auto Layout

Question

I\'m trying to get self sizing UICollectionViewCells working with Auto Layout, but I can\'t seem to get the cells to size themselves to the content. I\'m having

Answer 1

I did a dynamic cell height of collection view. Here is git hub repo.

And, dig out why preferredLayoutAttributesFittingAttributes is called more than once. Actually, it will be called at least 3 times.

The console log picture :

1st preferredLayoutAttributesFittingAttributes:

(lldb) po layoutAttributes
 index path: ( 
{length = 2, path = 0 - 0}); frame = (15 12; 384 57.5); 

(lldb) po self.collectionView

The layoutAttributes.frame.size.height is current status 57.5.

2nd preferredLayoutAttributesFittingAttributes:

(lldb) po layoutAttributes
 index path: ( 
{length = 2, path = 0 - 0}); frame = (15 12; 384 534.5); 

(lldb) po self.collectionView

The cell frame height changed to 534.5 as our expected. But, the collection view still zero height.

3rd preferredLayoutAttributesFittingAttributes:

(lldb) po layoutAttributes
 index path: ( 
{length = 2, path = 0 - 0}); frame = (15 12; 384 534.5); 

(lldb) po self.collectionView

You can see the collection view height was changed from 0 to 477.

The behavior is similar to handle scroll:

1. Before self-sizing cell

2. Validated self-sizing cell again after other cells recalculated.

3. Did changed self-sizing cell

At beginning, I thought this method only call once. So I coded as the following:

CGRect frame = layoutAttributes.frame;
frame.size.height = frame.size.height + self.collectionView.contentSize.height;
UICollectionViewLayoutAttributes* newAttributes = [layoutAttributes copy];
newAttributes.frame = frame;
return newAttributes;

This line:

frame.size.height = frame.size.height + self.collectionView.contentSize.height;

will cause system call infinite loop and App crash.

Any size changed, it will validate all cells' preferredLayoutAttributesFittingAttributes again and again until every cells' positions (i.e frames) are no more change.