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

The "just snap" answer above didn't work for me as it frequently didn't end on the item that was in view before the rotate. So I derived a flow layout that uses a focus item (if set) for calculating the content offset. I set the item in willAnimateRotationToInterfaceOrientation and clear it in didRotateFromInterfaceOrientation. The inset adjustment seems to be need on IOS7 because the Collection view can layout under the top bar.

@interface HintedFlowLayout : UICollectionViewFlowLayout
@property (strong)NSIndexPath* pathForFocusItem;
@end

@implementation HintedFlowLayout

-(CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset
{
    if (self.pathForFocusItem) {
        UICollectionViewLayoutAttributes* layoutAttrs = [self layoutAttributesForItemAtIndexPath:self.pathForFocusItem];
        return CGPointMake(layoutAttrs.frame.origin.x - self.collectionView.contentInset.left, layoutAttrs.frame.origin.y-self.collectionView.contentInset.top);
    }else{
        return [super targetContentOffsetForProposedContentOffset:proposedContentOffset];
    }
}
@end