UICollectionView wrong contentSize on first load, correct after that
objective-c, uicollectionview, uicollectionviewlayout
Solution
So I was seeing a similar issue where contentSize width was always zero. The simple answer is...there is probably no content in the collectionView yet. That was why it's content size is zero.
I was also noticing that sometimes after calling `invalidateLayout` on my UICollectionView, I was seeing that `self.collectionView.collectionViewLayout.collectionViewContentSize` was not the same as `self.collectionView.contentSize`.
After much searching I found a great hint here in this SO post
What I needed to do to get both contentSize calculations to be the same was to call `[self.collectionView layoutIfNeeded]` immediately after calling `[self.collectionView reloadData]` or `[self.collectionView.collectionViewLayout invalidateLayout]`.
This essentially forces the reload to happen immediately instead of on the next runloop cycle.
I really hope this solves your issue.
Problem
I have a common UICollectionView with paging and all. Still trying to figure out why on viewDidLoad:, viewWillAppear: and viewDidAppear: , only on first view call, I get the wrong size when calling myCollectionView.collectionView.contentSize.width. It always respond with 0 width (height is always correct). Successive reload of the view get me the correct one. Resorted to using ``` self.collectionView.collectionViewLayout.collectionViewContentSize ``` which give me the correct width event on first load. Still a mystery to me.