按单元格而不是屏幕分页 UICollectionView

好的，所以我在这里找到了解决方案：targetContentOffsetForProposedContentOffset:withScrollingVelocity without subclassing UICollectionViewFlowLayout

我应该在一开始就搜索 targetContentOffsetForProposedContentOffset。

---

只需覆盖该方法：

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
    *targetContentOffset = scrollView.contentOffset; // set acceleration to 0.0
    float pageWidth = (float)self.articlesCollectionView.bounds.size.width;
    int minSpace = 10;

    int cellToSwipe = (scrollView.contentOffset.x)/(pageWidth + minSpace) + 0.5; // cell width + min spacing for lines
    if (cellToSwipe < 0) {
        cellToSwipe = 0;
    } else if (cellToSwipe >= self.articles.count) {
        cellToSwipe = self.articles.count - 1;
    }
    [self.articlesCollectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForRow:cellToSwipe inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];
}

---

这是我在 Swift 5 中针对基于单元的垂直分页的实现：

override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {

    guard let collectionView = self.collectionView else {
        let latestOffset = super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)
        return latestOffset
    }

    // Page height used for estimating and calculating paging.
    let pageHeight = self.itemSize.height + self.minimumLineSpacing

    // Make an estimation of the current page position.
    let approximatePage = collectionView.contentOffset.y/pageHeight

    // Determine the current page based on velocity.
    let currentPage = velocity.y == 0 ? round(approximatePage) : (velocity.y < 0.0 ? floor(approximatePage) : ceil(approximatePage))

    // Create custom flickVelocity.
    let flickVelocity = velocity.y * 0.3

    // Check how many pages the user flicked, if <= 1 then flickedPages should return 0.
    let flickedPages = (abs(round(flickVelocity)) <= 1) ? 0 : round(flickVelocity)

    let newVerticalOffset = ((currentPage + flickedPages) * pageHeight) - collectionView.contentInset.top

    return CGPoint(x: proposedContentOffset.x, y: newVerticalOffset)
}

一些注意事项：

不会出错

设置分页为假！ （否则这将不起作用）

允许您轻松设置自己的轻弹速度。

如果尝试此操作后仍然无法正常工作，请检查您的 itemSize 是否实际上与项目的大小匹配，因为这通常是一个问题，尤其是在使用 collectionView(_:layout:sizeForItemAt:) 时，请改用带有 itemSize 的自定义变量。

这在您设置 self.collectionView.decelerationRate = UIScrollView.DecelerationRate.fast 时效果最佳。

这是一个横向版本（尚未彻底测试，所以请原谅任何错误）：

override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {

    guard let collectionView = self.collectionView else {
        let latestOffset = super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)
        return latestOffset
    }

    // Page width used for estimating and calculating paging.
    let pageWidth = self.itemSize.width + self.minimumInteritemSpacing

    // Make an estimation of the current page position.
    let approximatePage = collectionView.contentOffset.x/pageWidth

    // Determine the current page based on velocity.
    let currentPage = velocity.x == 0 ? round(approximatePage) : (velocity.x < 0.0 ? floor(approximatePage) : ceil(approximatePage))

    // Create custom flickVelocity.
    let flickVelocity = velocity.x * 0.3

    // Check how many pages the user flicked, if <= 1 then flickedPages should return 0.
    let flickedPages = (abs(round(flickVelocity)) <= 1) ? 0 : round(flickVelocity)

    // Calculate newHorizontalOffset.
    let newHorizontalOffset = ((currentPage + flickedPages) * pageWidth) - collectionView.contentInset.left

    return CGPoint(x: newHorizontalOffset, y: proposedContentOffset.y)
}

此代码基于我在个人项目中使用的代码，您可以通过下载它并运行示例目标来查看 here。

---

具有自定义页面宽度的水平分页（Swift 4 和 5）

这里介绍的许多解决方案会导致一些奇怪的行为，感觉不像是正确实现的分页。

但是，this tutorial 中提出的解决方案似乎没有任何问题。感觉就像一个完美的分页算法。您可以通过 5 个简单的步骤来实现它：

将以下属性添加到您的类型： private var indexOfCellBeforeDragging = 0 像这样设置 collectionView 委托： collectionView.delegate = self 通过扩展添加对 UICollectionViewDelegate 的一致性： extension YourType: UICollectionViewDelegate { } 将以下方法添加到实现 UICollectionViewDelegate 一致性的扩展并为 pageWidth 设置一个值： func scrollViewWillBeginDragging(_ scrollView: UIScrollView) { let pageWidth = // 你的页面应该有的宽度（加上可能的边距） let ratioOffset = collectionView.contentOffset.x / pageWidth indexOfCellBeforeDragging = Int(round(proportionalOffset )) } 将以下方法添加到实现 UICollectionViewDelegate 一致性的扩展中，为 pageWidth 设置相同的值（您也可以将此值存储在中心位置）并为 collectionViewItemCount 设置一个值： func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity ：CGPoint，目标内容偏移： UnsafeMutablePointer) { // 停止滚动 targetContentOffset.pointee = scrollView.contentOffset // 计算条件 let pageWidth = // 你的页面应该有的宽度（加上可能的边距） let collectionViewItemCount = // 本节中的项目数让proportionalOffset = collectionView.contentOffset.x / pageWidth 让indexOfMajorCell = Int(round(proportionalOffset)) 让swipeVelocityThreshold: CGFloat = 0.5 让hasEnoughVelocityToSlideToTheNextCell = indexOfCellBeforeDragging + 1 swipeVelocityThreshold 让hasEnoughVelocityToSlideToThePreviousCell = indexOfCell - &&BeforeDragging1=0 velocity.x < -swipeVelocityThreshold let majorCellIsTheCellBeforeDragging = indexOfMajorCell == indexOfCellBeforeDragging let didUseSwipeToSkipCell = majorCellIsTheCellBeforeDragging && (hasEnoughVelocityToSlideToTheNextCell || hasEnoughVelocityToSlideToThePreviousCell) if didUseSwipeToSkipCell { // 设置动画以便继续滑动 let snapToIndex = indexOfCellBeforeDragging + (hasEnoughVelocityToSlideToTheNextCell ? 1 : -1) let toValue = pageWidth * CGFloat(snapToIndex) UIView.animate( withDuration: 0.3, delay: 0, usingSpringWithDamping: 1、initialSpringVelocity: velocity.x, options: .allowUserInteraction, animations: { scrollView.contentOffset = CGPoint(x: toValue, y: 0) scrollView.layoutIfNeeded() }, completion: nil ) } else { // 弹回（反对速度) 让 indexPath = IndexPath(row: indexOfMajorCell, section: 0) collectionView.scrollToItem(at: indexPath, at: .left, 动画: true) } }

---

这是我在 Swift 4.2 中发现的用于水平滚动的最简单方法：

我正在使用 visibleCells 上的第一个单元格并滚动到该单元格，如果第一个可见单元格显示的宽度小于其宽度的一半，我将滚动到下一个单元格。

如果您的收藏垂直滚动，只需将 x 更改为 y 并将 width 更改为 height

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    targetContentOffset.pointee = scrollView.contentOffset
    var indexes = self.collectionView.indexPathsForVisibleItems
    indexes.sort()
    var index = indexes.first!
    let cell = self.collectionView.cellForItem(at: index)!
    let position = self.collectionView.contentOffset.x - cell.frame.origin.x
    if position > cell.frame.size.width/2{
       index.row = index.row+1
    }
    self.collectionView.scrollToItem(at: index, at: .left, animated: true )
}

---

Evya 回答的 Swift 3 版本：

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
  targetContentOffset.pointee = scrollView.contentOffset
    let pageWidth:Float = Float(self.view.bounds.width)
    let minSpace:Float = 10.0
    var cellToSwipe:Double = Double(Float((scrollView.contentOffset.x))/Float((pageWidth+minSpace))) + Double(0.5)
    if cellToSwipe < 0 {
        cellToSwipe = 0
    } else if cellToSwipe >= Double(self.articles.count) {
        cellToSwipe = Double(self.articles.count) - Double(1)
    }
    let indexPath:IndexPath = IndexPath(row: Int(cellToSwipe), section:0)
    self.collectionView.scrollToItem(at:indexPath, at: UICollectionViewScrollPosition.left, animated: true)


}

---

部分基于 StevenOjo 的回答。我已经使用水平滚动和没有 Bounce UICollectionView 对此进行了测试。 cellSize 是 CollectionViewCell 的大小。您可以调整因子以修改滚动灵敏度。

override func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    targetContentOffset.pointee = scrollView.contentOffset
    var factor: CGFloat = 0.5
    if velocity.x < 0 {
        factor = -factor
    }
    let indexPath = IndexPath(row: (scrollView.contentOffset.x/cellSize.width + factor).int, section: 0)
    collectionView?.scrollToItem(at: indexPath, at: .left, animated: true)
}

---

方法一：集合视图

flowLayout 是 UICollectionViewFlowLayout 属性

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

    if let collectionView = collectionView {

        targetContentOffset.memory = scrollView.contentOffset
        let pageWidth = CGRectGetWidth(scrollView.frame) + flowLayout.minimumInteritemSpacing

        var assistanceOffset : CGFloat = pageWidth / 3.0

        if velocity.x < 0 {
            assistanceOffset = -assistanceOffset
        }

        let assistedScrollPosition = (scrollView.contentOffset.x + assistanceOffset) / pageWidth

        var targetIndex = Int(round(assistedScrollPosition))


        if targetIndex < 0 {
            targetIndex = 0
        }
        else if targetIndex >= collectionView.numberOfItemsInSection(0) {
            targetIndex = collectionView.numberOfItemsInSection(0) - 1
        }

        print("targetIndex = \(targetIndex)")

        let indexPath = NSIndexPath(forItem: targetIndex, inSection: 0)

        collectionView.scrollToItemAtIndexPath(indexPath, atScrollPosition: .Left, animated: true)
    }
}

方法 2：页面视图控制器

如果满足您的要求，您可以使用 UIPageViewController，每个页面都有一个单独的视图控制器。

---

修改 Romulo BM 答案以进行速度监听

func scrollViewWillEndDragging(
    _ scrollView: UIScrollView,
    withVelocity velocity: CGPoint,
    targetContentOffset: UnsafeMutablePointer<CGPoint>
) {
    targetContentOffset.pointee = scrollView.contentOffset
    var indexes = collection.indexPathsForVisibleItems
    indexes.sort()
    var index = indexes.first!
    if velocity.x > 0 {
       index.row += 1
    } else if velocity.x == 0 {
        let cell = self.collection.cellForItem(at: index)!
        let position = self.collection.contentOffset.x - cell.frame.origin.x
        if position > cell.frame.size.width / 2 {
           index.row += 1
        }
    }

    self.collection.scrollToItem(at: index, at: .centeredHorizontally, animated: true )
}

---

这是 Swift5 中的优化解决方案，包括处理错误的 indexPath。 - 迈克尔林刘

步骤1。获取当前单元格的 indexPath。

第2步。检测滚动时的速度。

第三步。当速度增加时增加 indexPath 的行。

第4步。告诉集合视图滚动到下一个项目

    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        
        targetContentOffset.pointee = scrollView.contentOffset
        
        //M: Get the first visiable item's indexPath from visibaleItems.
        var indexPaths = *YOURCOLLECTIONVIEW*.indexPathsForVisibleItems
        indexPaths.sort()
        var indexPath = indexPaths.first!

        //M: Use the velocity to detect the paging control movement.
        //M: If the movement is forward, then increase the indexPath.
        if velocity.x > 0{
            indexPath.row += 1
            
            //M: If the movement is in the next section, which means the indexPath's row is out range. We set the indexPath to the first row of the next section.
            if indexPath.row == *YOURCOLLECTIONVIEW*.numberOfItems(inSection: indexPath.section){
                indexPath.row = 0
                indexPath.section += 1
            }
        }
        else{
            //M: If the movement is backward, the indexPath will be automatically changed to the first visiable item which is indexPath.row - 1. So there is no need to write the logic.
        }
        
        //M: Tell the collection view to scroll to the next item.
        *YOURCOLLECTIONVIEW*.scrollToItem(at: indexPath, at: .left, animated: true )
 }

---

这是执行此操作的直接方法。

案例很简单，但最后很常见（典型的缩略图滚动器，具有固定的单元格大小和固定的单元格之间的间隙）

var itemCellSize: CGSize = <your cell size>
var itemCellsGap: CGFloat = <gap in between>

override func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    let pageWidth = (itemCellSize.width + itemCellsGap)
    let itemIndex = (targetContentOffset.pointee.x) / pageWidth
    targetContentOffset.pointee.x = round(itemIndex) * pageWidth - (itemCellsGap / 2)
}

// CollectionViewFlowLayoutDelegate

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return itemCellSize
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return itemCellsGap
}

请注意，没有理由调用 scrollToOffset 或深入布局。本机滚动行为已经完成了一切。

祝大家好运:)

---

有点像 evya 的答案，但更平滑一些，因为它没有将 targetContentOffset 设置为零。

- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
    if ([scrollView isKindOfClass:[UICollectionView class]]) {
        UICollectionView* collectionView = (UICollectionView*)scrollView;
        if ([collectionView.collectionViewLayout isKindOfClass:[UICollectionViewFlowLayout class]]) {
            UICollectionViewFlowLayout* layout = (UICollectionViewFlowLayout*)collectionView.collectionViewLayout;

            CGFloat pageWidth = layout.itemSize.width + layout.minimumInteritemSpacing;
            CGFloat usualSideOverhang = (scrollView.bounds.size.width - pageWidth)/2.0;
            // k*pageWidth - usualSideOverhang = contentOffset for page at index k if k >= 1, 0 if k = 0
            // -> (contentOffset + usualSideOverhang)/pageWidth = k at page stops

            NSInteger targetPage = 0;
            CGFloat currentOffsetInPages = (scrollView.contentOffset.x + usualSideOverhang)/pageWidth;
            targetPage = velocity.x < 0 ? floor(currentOffsetInPages) : ceil(currentOffsetInPages);
            targetPage = MAX(0,MIN(self.projects.count - 1,targetPage));

            *targetContentOffset = CGPointMake(MAX(targetPage*pageWidth - usualSideOverhang,0), 0);
        }
    }
}

---

这是我在 Swift 3 中的版本。计算滚动结束后的偏移量并用动画调整偏移量。

collectionLayout 是一个 UICollectionViewFlowLayout()

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    let index = scrollView.contentOffset.x / collectionLayout.itemSize.width
    let fracPart = index.truncatingRemainder(dividingBy: 1)
    let item= Int(fracPart >= 0.5 ? ceil(index) : floor(index))

    let indexPath = IndexPath(item: item, section: 0)
    collectionView.scrollToItem(at: indexPath, at: .left, animated: true)
}

---

斯威夫特 5

我找到了一种无需子类化 UICollectionView 的方法，只需计算水平方向的 contentOffset。显然没有 isPagingEnabled 设置为 true。这是代码：

var offsetScroll1 : CGFloat = 0
var offsetScroll2 : CGFloat = 0
let flowLayout = UICollectionViewFlowLayout()
let screenSize : CGSize = UIScreen.main.bounds.size
var items = ["1", "2", "3", "4", "5"]

override func viewDidLoad() {
    super.viewDidLoad()
    flowLayout.scrollDirection = .horizontal
    flowLayout.minimumLineSpacing = 7
    let collectionView = UICollectionView(frame: CGRect(x: 0, y: 590, width: screenSize.width, height: 200), collectionViewLayout: flowLayout)
    collectionView.register(collectionViewCell1.self, forCellWithReuseIdentifier: cellReuseIdentifier)
    collectionView.delegate = self
    collectionView.dataSource = self
    collectionView.backgroundColor = UIColor.clear
    collectionView.showsHorizontalScrollIndicator = false
    self.view.addSubview(collectionView)
}

func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
    offsetScroll1 = offsetScroll2
}

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    offsetScroll1 = offsetScroll2
}

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>){
    let indexOfMajorCell = self.desiredIndex()
    let indexPath = IndexPath(row: indexOfMajorCell, section: 0)
    flowLayout.collectionView!.scrollToItem(at: indexPath, at: .centeredHorizontally, animated: true)
    targetContentOffset.pointee = scrollView.contentOffset
}

private func desiredIndex() -> Int {
    var integerIndex = 0
    print(flowLayout.collectionView!.contentOffset.x)
    offsetScroll2 = flowLayout.collectionView!.contentOffset.x
    if offsetScroll2 > offsetScroll1 {
        integerIndex += 1
        let offset = flowLayout.collectionView!.contentOffset.x / screenSize.width
        integerIndex = Int(round(offset))
        if integerIndex < (items.count - 1) {
            integerIndex += 1
        }
    }
    if offsetScroll2 < offsetScroll1 {
        let offset = flowLayout.collectionView!.contentOffset.x / screenSize.width
        integerIndex = Int(offset.rounded(.towardZero))
    }
    let targetIndex = integerIndex
    return targetIndex
}

---

您还可以创建假滚动视图来处理滚动。

水平或垂直

// === Defaults ===
let bannerSize = CGSize(width: 280, height: 170)
let pageWidth: CGFloat = 290 // ^ + paging
let insetLeft: CGFloat = 20
let insetRight: CGFloat = 20
// ================

var pageScrollView: UIScrollView!

override func viewDidLoad() {
    super.viewDidLoad()

    // Create fake scrollview to properly handle paging
    pageScrollView = UIScrollView(frame: CGRect(origin: .zero, size: CGSize(width: pageWidth, height: 100)))
    pageScrollView.isPagingEnabled = true
    pageScrollView.alwaysBounceHorizontal = true
    pageScrollView.showsVerticalScrollIndicator = false
    pageScrollView.showsHorizontalScrollIndicator = false
    pageScrollView.delegate = self
    pageScrollView.isHidden = true
    view.insertSubview(pageScrollView, belowSubview: collectionView)

    // Set desired gesture recognizers to the collection view
    for gr in pageScrollView.gestureRecognizers! {
        collectionView.addGestureRecognizer(gr)
    }
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    if scrollView == pageScrollView {
        // Return scrolling back to the collection view
        collectionView.contentOffset.x = pageScrollView.contentOffset.x
    }
}

func refreshData() {
    ...

    refreshScroll()
}

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

    refreshScroll()
}

/// Refresh fake scrolling view content size if content changes
func refreshScroll() {
    let w = collectionView.width - bannerSize.width - insetLeft - insetRight
    pageScrollView.contentSize = CGSize(width: pageWidth * CGFloat(banners.count) - w, height: 100)
}

---

这是我的解决方案，在 Swift 4.2 中，我希望它可以帮助你。

class SomeViewController: UIViewController {

  private lazy var flowLayout: UICollectionViewFlowLayout = {
    let layout = UICollectionViewFlowLayout()
    layout.itemSize = CGSize(width: /* width */, height: /* height */)
    layout.minimumLineSpacing = // margin
    layout.minimumInteritemSpacing = 0.0
    layout.sectionInset = UIEdgeInsets(top: 0.0, left: /* margin */, bottom: 0.0, right: /* margin */)
    layout.scrollDirection = .horizontal
    return layout
  }()

  private lazy var collectionView: UICollectionView = {
    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: flowLayout)
    collectionView.showsHorizontalScrollIndicator = false
    collectionView.dataSource = self
    collectionView.delegate = self
    // collectionView.register(SomeCell.self)
    return collectionView
  }()

  private var currentIndex: Int = 0
}

// MARK: - UIScrollViewDelegate

extension SomeViewController {
  func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
    guard scrollView == collectionView else { return }

    let pageWidth = flowLayout.itemSize.width + flowLayout.minimumLineSpacing
    currentIndex = Int(scrollView.contentOffset.x / pageWidth)
  }

  func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    guard scrollView == collectionView else { return }

    let pageWidth = flowLayout.itemSize.width + flowLayout.minimumLineSpacing
    var targetIndex = Int(roundf(Float(targetContentOffset.pointee.x / pageWidth)))
    if targetIndex > currentIndex {
      targetIndex = currentIndex + 1
    } else if targetIndex < currentIndex {
      targetIndex = currentIndex - 1
    }
    let count = collectionView.numberOfItems(inSection: 0)
    targetIndex = max(min(targetIndex, count - 1), 0)
    print("targetIndex: \(targetIndex)")

    targetContentOffset.pointee = scrollView.contentOffset
    var offsetX: CGFloat = 0.0
    if targetIndex < count - 1 {
      offsetX = pageWidth * CGFloat(targetIndex)
    } else {
      offsetX = scrollView.contentSize.width - scrollView.width
    }
    collectionView.setContentOffset(CGPoint(x: offsetX, y: 0.0), animated: true)
  }
}

---

Олень Безрогий 的原始答案有问题，所以在最后一个单元格集合视图上滚动到开头

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    targetContentOffset.pointee = scrollView.contentOffset
    var indexes = yourCollectionView.indexPathsForVisibleItems
    indexes.sort()
    var index = indexes.first!
    // if velocity.x > 0 && (Get the number of items from your data) > index.row + 1 {
    if velocity.x > 0 && yourCollectionView.numberOfItems(inSection: 0) > index.row + 1 {
       index.row += 1
    } else if velocity.x == 0 {
        let cell = yourCollectionView.cellForItem(at: index)!
        let position = yourCollectionView.contentOffset.x - cell.frame.origin.x
        if position > cell.frame.size.width / 2 {
           index.row += 1
        }
    }
    
    yourCollectionView.scrollToItem(at: index, at: .centeredHorizontally, animated: true )
}

---

好的，所以建议的答案对我不起作用，因为我想按部分滚动，因此页面大小可变

我这样做了（仅限垂直）：

   var pagesSizes = [CGSize]()
   func scrollViewDidScroll(_ scrollView: UIScrollView) {
        defer {
            lastOffsetY = scrollView.contentOffset.y
        }
        if collectionView.isDecelerating {
            var currentPage = 0
            var currentPageBottom = CGFloat(0)
            for pagesSize in pagesSizes {
                currentPageBottom += pagesSize.height
                if currentPageBottom > collectionView!.contentOffset.y {
                    break
                }
                currentPage += 1
            }
            if collectionView.contentOffset.y > currentPageBottom - pagesSizes[currentPage].height, collectionView.contentOffset.y + collectionView.frame.height < currentPageBottom {
                return // 100% of view within bounds
            }
            if lastOffsetY < collectionView.contentOffset.y {
                if currentPage + 1 != pagesSizes.count {
                    collectionView.setContentOffset(CGPoint(x: 0, y: currentPageBottom), animated: true)
                }
            } else {
                collectionView.setContentOffset(CGPoint(x: 0, y: currentPageBottom - pagesSizes[currentPage].height), animated: true)
            }
        }
    }

在这种情况下，我使用节高 + 页眉 + 页脚预先计算每个页面大小，并将其存储在数组中。那是 pagesSizes 成员

---

我创建了一个自定义集合视图布局 here，它支持：

一次分页一个单元格

根据滑动速度一次分页 2+ 个单元格

水平或垂直方向

这很简单：

let layout = PagingCollectionViewLayout()

layout.itemSize = 
layout.minimumLineSpacing = 
layout.scrollDirection = 

您只需将 PagingCollectionViewLayout.swift 添加到您的项目中

或者

将 pod 'PagingCollectionViewLayout' 添加到您的 podfile

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final class PagingFlowLayout: UICollectionViewFlowLayout {
    private var currentIndex = 0

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
        let count = collectionView!.numberOfItems(inSection: 0)
        let currentAttribute = layoutAttributesForItem(
            at: IndexPath(item: currentIndex, section: 0)
            ) ?? UICollectionViewLayoutAttributes()

        let direction = proposedContentOffset.x > currentAttribute.frame.minX
        if collectionView!.contentOffset.x + collectionView!.bounds.width < collectionView!.contentSize.width || currentIndex < count - 1 {
            currentIndex += direction ? 1 : -1
            currentIndex = max(min(currentIndex, count - 1), 0)
        }

        let indexPath = IndexPath(item: currentIndex, section: 0)
        let closestAttribute = layoutAttributesForItem(at: indexPath) ?? UICollectionViewLayoutAttributes()

        let centerOffset = collectionView!.bounds.size.width / 2
        return CGPoint(x: closestAttribute.center.x - centerOffset, y: 0)
    }
}

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func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity 
velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    targetContentOffset.pointee = scrollView.contentOffset
    var indexes = self.collectionHome.indexPathsForVisibleItems
    indexes.sort()
    var index = indexes.first!
    let cell = self.collectionHome.cellForItem(at: index)!
    let position = self.collectionHome.contentOffset.x - cell.frame.origin.x
    if position > cell.frame.size.width/2{
        index.row = index.row+1
    }
    self.collectionHome.scrollToItem(at: index, at: .left, animated: true )
}

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这是我见过的最好的解决方案。只需将它与 .linear 类型一起使用。 https://github.com/nicklockwood/iCarousel 上帝保佑作者！:)

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这是我使用 UICollectionViewFlowLayout 覆盖 targetContentOffset 的方法：

（虽然最后，我最终没有使用它，而是使用 UIPageViewController。）

/**
 A UICollectionViewFlowLayout with...
 - paged horizontal scrolling
 - itemSize is the same as the collectionView bounds.size
 */
class PagedFlowLayout: UICollectionViewFlowLayout {

  override init() {
    super.init()
    self.scrollDirection = .horizontal
    self.minimumLineSpacing = 8 // line spacing is the horizontal spacing in horizontal scrollDirection
    self.minimumInteritemSpacing = 0
    if #available(iOS 11.0, *) {
      self.sectionInsetReference = .fromSafeArea // for iPhone X
    }
  }

  required init?(coder aDecoder: NSCoder) {
    fatalError("not implemented")
  }

  // Note: Setting `minimumInteritemSpacing` here will be too late. Don't do it here.
  override func prepare() {
    super.prepare()
    guard let collectionView = collectionView else { return }
    collectionView.decelerationRate = UIScrollViewDecelerationRateFast // mostly you want it fast!

    let insetedBounds = UIEdgeInsetsInsetRect(collectionView.bounds, self.sectionInset)
    self.itemSize = insetedBounds.size
  }

  // Table: Possible cases of targetContentOffset calculation
  // -------------------------
  // start |          |
  // near  | velocity | end
  // page  |          | page
  // -------------------------
  //   0   | forward  |  1
  //   0   | still    |  0
  //   0   | backward |  0
  //   1   | forward  |  1
  //   1   | still    |  1
  //   1   | backward |  0
  // -------------------------
  override func targetContentOffset( //swiftlint:disable:this cyclomatic_complexity
    forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {

    guard let collectionView = collectionView else { return proposedContentOffset }

    let pageWidth = itemSize.width + minimumLineSpacing
    let currentPage: CGFloat = collectionView.contentOffset.x / pageWidth
    let nearestPage: CGFloat = round(currentPage)
    let isNearPreviousPage = nearestPage < currentPage

    var pageDiff: CGFloat = 0
    let velocityThreshold: CGFloat = 0.5 // can customize this threshold
    if isNearPreviousPage {
      if velocity.x > velocityThreshold {
        pageDiff = 1
      }
    } else {
      if velocity.x < -velocityThreshold {
        pageDiff = -1
      }
    }

    let x = (nearestPage + pageDiff) * pageWidth
    let cappedX = max(0, x) // cap to avoid targeting beyond content
    //print("x:", x, "velocity:", velocity)
    return CGPoint(x: cappedX, y: proposedContentOffset.y)
  }

}

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您可以使用以下库：https://github.com/ink-spot/UPCarouselFlowLayout

这非常简单，您不需要考虑其他答案所包含的细节。

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