UICollectionView scroll to item not working with horizontal direction

问题

I have a UICollectionView within a UIViewController with paging enabled. For some strange reason collectionView.scrollToItem works when the direction of the collectionview is vertical but doesn't when direction is horizontal. Is this there something I'm doing wrong or is this supposed to happen?

  //Test scrollToItem
  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let i = IndexPath(item: 3, section: 0)
    collectionView.reloadData()
      collectionView.scrollToItem(at: i, at: .top, animated: true)
      print("Selected")
  }

回答1:

For this part:

collectionView.scrollToItem(at: i, at: .top, animated: true)

When the scroll direction is horizontal you need to use at: left, at: right or at: centeredHorizontally. at: top is for vertical direction.

回答2:

I had trouble implementing this in a flow layout with entered paging per item. The .centeredHorizontally just wouldn't work for me so i use scroll to rect and Check there is data before scrolling:

    if self.collectionView?.dataSource?.collectionView(self.collectionView!, cellForItemAt: IndexPath(row: 0, section: 0)) != nil {
        let rect = self.collectionView.layoutAttributesForItem(at: IndexPath(item: data[index], section: 0))?.frame
        self.collectionView.scrollRectToVisible(rect!, animated: false)
    }

回答3:

Swift 5.1, Xcode 11.2.1

collectionView.scrollToItem(at: IndexPath(item: pageNumber , section: 0), at: .centeredHorizontally, animated: true)
self.collectionView.setNeedsLayout() // **Without this effect wont be visible**

回答4:

Swift 3:

This worked for me on horizontal collection view.

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

//Show 14th row as first row
self.activityCollectionView?.scrollToItem(at: IndexPath(row: 14, section: 0), at: UICollectionViewScrollPosition.right, animated: true)
}

You can choose whether the desired cell at index to be on right or left on scroll position.

UICollectionViewScrollPosition.right or UICollectionViewScrollPosition.left.

回答5:

For scrolling the item, there is no need to reloadData. Remove below line from your code and try.

collectionView.reloadData()

回答6:

For me, I had to scroll collection view on main thread like,

    DispatchQueue.main.async {
        self.collectionView.scrollToItem(at: IndexPath(item: index, section: 0), at: .centeredHorizontally, animated: true)
    }

来源：https://stackoverflow.com/questions/41884645/uicollectionview-scroll-to-item-not-working-with-horizontal-direction

标签

ios

swift

uicollectionview