Keeping the contentOffset in a UICollectionView while rotating Interface Orientation

Question

I\'m trying to handle interface orientation changes in a UICollectionViewController. What I\'m trying to achieve is, that I want to have the same contentOffset afte

Answer 1

in Swift 3.

you should track which cell item(Page) is being presented before rotate by indexPath.item, the x coordinate or something else. Then, in your UICollectionView:

override func collectionView(_ collectionView: UICollectionView, targetContentOffsetForProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint {

    let page:CGFloat = pageNumber // your tracked page number eg. 1.0
    return CGPoint(x: page * collectionView.frame.size.width, y: -(topInset))
    //the 'y' value would be '0' if you don't have any top EdgeInset
}

In my case I invalidate the layout in viewDidLayoutSubviews() so the collectionView.frame.size.width is the width of the collectionVC's view that has been rotated.