layoutAttributesForItemAtIndexPath doesn't return the actual position when performing peek and pop

Question

I am trying to implement Peek and Pop to preview the image on photo library with the following code:

func previewingContext(previewingContext: UIViewControllerPreviewing, viewControllerForLocation location: CGPoint) -> UIViewController? {
    if let indexPath = self.collectionView!.indexPathForItemAtPoint(location), cellAttributes = self.collectionView!.layoutAttributesForItemAtIndexPath(indexPath) {

        previewingContext.sourceRect = cellAttributes.frame
    }

    let selectedPhotoAsset = self.allPhotos[self.selectedPhotoIndexPath![0].item] as! PHAsset

    guard let displayImageDetailVC = storyboard?.instantiateViewControllerWithIdentifier("DisplayImageDetailVC") as? DisplayImageViewController else {
        print("Error instantiate DisplayImageDetail View Controller")
        return nil
    }

    displayImageDetailVC.selectedPhotoAsset = selectedPhotoAsset

    return displayImageDetailVC
}

Even though it works, but the problem is after the collection view scrolled, the preview area sometimes is not at the exact cell's position when trying to peek.

Is there any way that I can get the actual position of the cell?

Answer 1

I have found the solution for this issue, turns out it is related to registerForPreviewingWithDelegate.

Instead of

registerForPreviewingWithDelegate(self, sourceView: view)

It should be

registerForPreviewingWithDelegate(self, sourceView: self.collectionView!)