UICollectionView滚动到不使用水平方向的项目

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?

我在UIViewController中有一个启用了分页的UICollectionView。由于一些奇怪的原因，collectionView.scrollToItem在collectionview的方向是垂直的时候工作，但是当方向是水平的时候不工作。这有什么我做错了还是这应该发生？

  //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")
  }

4 个解决方案

#1

For this part:

对于这部分：

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

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.

当滚动方向为水平时，您需要使用at：left，at：right或at：centeredHorizontally。 at：top表示垂直方向。

#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:

我在流程布局中实现这一点时遇到了麻烦，每个项目都输入了分页。 .centeredHorizontally对我来说不起作用所以我使用滚动到rect并在滚动之前检查数据：

    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)
    }

#3

Swift 3:

斯威夫特3：

This worked for me on horizontal collection view.

这在横向集合视图中对我有用。

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.

您可以选择索引处的所需单元格是否在滚动位置的右侧或左侧。

UICollectionViewScrollPosition.right or UICollectionViewScrollPosition.left.

#4

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

要滚动项目，不需要reloadData。从代码中删除以下行并尝试。

collectionView.reloadData()

#1