CODEWITHSUNDEEP
iosswiftcollections
Uffo
Uffo

Reputation: 10056

Swift CollectionView set where to scroll

So I have a collection view horizontal and I want when the user scroll to set the scroll where I want.

@IBOutlet var joke_cards: UICollectionView!

extension ViewController: UIScrollViewDelegate{

    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {

        joke_cards.contentOffset.x = scrollView.contentOffset.x + 1000
        joke_cards.reloadData()

    }

}

But this doesn't work, it scrolls normally, I want to specify how much to scroll, any suggestions?

So I think I need to be a bit more clear, what I want is to flip through some cards horizontally thats why I need when the user stars to swipe to show the next cell in the middle

Upvotes: 0

Views: 1519

Answers (1)

creeperspeak
creeperspeak

Reputation: 5521

If you want to manually scroll the user to a certain area you need first to define the area you need to scroll into view. This will depend a little bit on where exactly you are trying to scroll, but if the goal is just to scroll 1000 points to the right you can define the rect and scrolling like so:

let destinationRect = CGRect(x: scrollView.contentOffset.x + 1000, y: scrollView.contentOffset.y, width: 1, height: 1)
scrollView.scrollRectToVisible(destinationRect, animated: true)

Please note that scrolling will stop as soon as any part of the rect is visible, so if you want contentOffset.x + 1000 to be in the center you will need to do some more math to create the destinationRect.

The other option, since you are using a UICollectionView is to figure out which cell is at the point you want to scroll to, and scroll that cell to a certain position. In this example I safely unwrap the optional indexPath at the point you specified, and scroll that cell to be centered horizontally in the collectionView:

if let indexPath = self.joke_cards.indexPathForItem(at: CGPoint(x: scrollView.contentOffset.x, y: scrollView.frame.midY)) {
    self.joke_cards.scrollToItem(at: indexPath, at: .centeredHorizontally, animated: true)
}

Upvotes: 1

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