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

I use a variant of fz. answer (iOS 7 & 8) :

Before rotation :

1. Store the current visible index path
2. Create a snapshot of the collectionView
3. Put an UIImageView with it on top of the collection view

After rotation :

1. Scroll to the stored index

2. Remove the image view.

   @property (nonatomic) NSIndexPath *indexPath;
   
   - (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
                                   duration:(NSTimeInterval)duration {
       self.indexPathAfterRotation = [[self.collectionView indexPathsForVisibleItems] firstObject];
   
       // Creates a temporary imageView that will occupy the full screen and rotate.
       UIGraphicsBeginImageContextWithOptions(self.collectionView.bounds.size, YES, 0);
       [self.collectionView drawViewHierarchyInRect:self.collectionView.bounds afterScreenUpdates:YES];
       UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
       UIGraphicsEndImageContext();
   
       UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
       [imageView setFrame:[self.collectionView bounds]];
       [imageView setTag:kTemporaryImageTag];
       [imageView setBackgroundColor:[UIColor blackColor]];
       [imageView setContentMode:UIViewContentModeCenter];
       [imageView setAutoresizingMask:0xff];
       [self.view insertSubview:imageView aboveSubview:self.collectionView];
   
       [[self.collectionView collectionViewLayout] invalidateLayout];
   }
   
   - (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {
       [self.collectionView scrollToItemAtIndexPath:self.indexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO];
   
       [[self.view viewWithTag:kTemporaryImageTag] removeFromSuperview];
   }