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

To piggy back off troppoli's solution you can set the offset in your custom class without having to worry about remembering to implement the code in your view controller. prepareForAnimatedBoundsChange should get called when you rotate the device then finalizeAnimatedBoundsChange after its done rotating.

@interface OrientationFlowLayout ()

@property (strong)NSIndexPath* pathForFocusItem;

@end

@implementation OrientationFlowLayout

- (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];
    }
}

- (void)prepareForAnimatedBoundsChange:(CGRect)oldBounds {
    [super prepareForAnimatedBoundsChange:oldBounds];
    self.pathForFocusItem = [[self.collectionView indexPathsForVisibleItems] firstObject];
}

- (void)finalizeAnimatedBoundsChange {
    [super finalizeAnimatedBoundsChange];
    self.pathForFocusItem = nil;
}

@end