CODEWITHSUNDEEP
objective-ciosxcodeuicollectionviewuicollectionviewcell
Dan Lister
Dan Lister

Reputation: 2583

How to find a UICollectionViewCell's coordinates relative to the App Window

Is it possible to translate a UICollectionViewCell's coordinates from being relative to the UICollectionView to being relative to the superview? So far I've been unable to translate a UICollectionViewCell's coordinates when touched to the superview. Here's what I've tried so far:

- (void)collectionView:(UICollectionView *)collectionView  
        didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = 
     [collectionView dequeueReusableCellWithReuseIdentifier:@"CollectionViewCell" 
                                               forIndexPath:indexPath];

    CGRect frame = CGRectMake(0.0, 
                              0.0,  
                              cell.frame.size.width, 
                              cell.frame.size.height);
    frame.origin = [cell convertPoint:cell.frame.origin 
                               toView:self.view];
}

I'd like to create a new frame which originates from the cell's position on the view, not in the UICollectionView. Any help would be great thanks.

Upvotes: 10

Views: 12288

Answers (3)

AydinAngouti
AydinAngouti

Reputation: 379

Just in case if anybody looking for this, here is how it can be done in Swift:

let cellFrameInSuperview = collectionView.convertRect(collectionView.cellForItemAtIndexPath(indexPath)!.frame, toView: view)

Upvotes: 3

Jay Slupesky
Jay Slupesky

Reputation: 1913

If I understand you correctly, I think the problem is that you first have to correct for the scroll view's contentOffset, which is easy to do since UICollectionView is a subclass of UIScrollView.

CGRect frame = CGRectMake(0.0,
                          0.0,
                          cell.frame.size.width,
                          cell.frame.size.height);
CGPoint correctedOffset = 
 CGPointMake(cell.frame.origin.x - collectionView.contentOffset.x,
             cell.frame.origin.y - collectionView.contentOffset.y);
frame.origin = [cell convertPoint:correctedOffset toView:self.view];

I tested this in one of my UICollectionView demo apps and it seems to work. Give it a try.

Upvotes: 4

LeStro
LeStro

Reputation: 378

This answer is very late, but hopefully it will help someone. Dan, you have the right idea, but it is even easier that what you have. Just replace

CGRect frame = CGRectMake(0.0, 0.0, cell.frame.size.width, cell.frame.size.height);
frame.origin = [cell convertPoint:cell.frame.origin toView:self.view];

with

CGRect frame = [collectionView convertRect:cell.frame toView:self.view];

The problem was that you were calling the convert method on the cell, not the collectionView.

Upvotes: 36

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