Ios 是否可以在Swift中创建带有动画页面控件的滚动视图？

设计师希望通过滑动手势获得以下动画

正如可以看到的，用户可以刷卡，看看每张卡都有什么。同时，用户可以在屏幕右侧看到下面的卡和左侧的最后一张卡。此外，当用户移动滚动条时，卡片会改变其大小

我已经使用过页面控件视图，但我不知道是否可以使用页面控件（这实际上是本文的问题）

此外，我已经尝试使用collectionView，但当我滑动（实际上是水平滚动）时，滚动有一个令人不舒服的惯性，而且，我不知道如何制作动画

在一个滚动页面控件实现，但现在我只是想知道，如果像gif提供的动画和动画是可能的

如果答案是肯定的，如果你能给我一些建议，我会非常感激

---

提前感谢。

根据Denislava Shentova的评论，我找到了一个很好的库来解决这个问题

对于未来的所有人和他们的工作时间，我只是从中提取代码并删除一些我不需要的代码

以下是显示以下结果的简单viewController的代码：

请注意，此代码中还有一些其他类别，但暂时可以在ViewController.swift文件中运行整个代码。测试后，请将它们拆分为不同的文件

为了运行此代码，您需要以下模块。制作一个名为UPCarouselFlowLayout.swift的文件并粘贴所有代码：

import UIKit


public enum UPCarouselFlowLayoutSpacingMode {
    case fixed(spacing: CGFloat)
    case overlap(visibleOffset: CGFloat)
}


open class UPCarouselFlowLayout: UICollectionViewFlowLayout {

    fileprivate struct LayoutState {
        var size: CGSize
        var direction: UICollectionViewScrollDirection
        func isEqual(_ otherState: LayoutState) -> Bool {
            return self.size.equalTo(otherState.size) && self.direction == otherState.direction
        }
    }

    @IBInspectable open var sideItemScale: CGFloat = 0.6
    @IBInspectable open var sideItemAlpha: CGFloat = 0.6
    open var spacingMode = UPCarouselFlowLayoutSpacingMode.fixed(spacing: 40)

    fileprivate var state = LayoutState(size: CGSize.zero, direction: .horizontal)


    override open func prepare() {
        super.prepare()

        let currentState = LayoutState(size: self.collectionView!.bounds.size, direction: self.scrollDirection)

        if !self.state.isEqual(currentState) {
            self.setupCollectionView()
            self.updateLayout()
            self.state = currentState
        }
    }

    fileprivate func setupCollectionView() {
        guard let collectionView = self.collectionView else { return }
        if collectionView.decelerationRate != UIScrollViewDecelerationRateFast {
            collectionView.decelerationRate = UIScrollViewDecelerationRateFast
        }
    }

    fileprivate func updateLayout() {
        guard let collectionView = self.collectionView else { return }

        let collectionSize = collectionView.bounds.size
        let isHorizontal = (self.scrollDirection == .horizontal)

        let yInset = (collectionSize.height - self.itemSize.height) / 2
        let xInset = (collectionSize.width - self.itemSize.width) / 2
        self.sectionInset = UIEdgeInsetsMake(yInset, xInset, yInset, xInset)

        let side = isHorizontal ? self.itemSize.width : self.itemSize.height
        let scaledItemOffset =  (side - side*self.sideItemScale) / 2
        switch self.spacingMode {
        case .fixed(let spacing):
            self.minimumLineSpacing = spacing - scaledItemOffset
        case .overlap(let visibleOffset):
            let fullSizeSideItemOverlap = visibleOffset + scaledItemOffset
            let inset = isHorizontal ? xInset : yInset
            self.minimumLineSpacing = inset - fullSizeSideItemOverlap
        }
    }

    override open func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }

    override open func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let superAttributes = super.layoutAttributesForElements(in: rect),
            let attributes = NSArray(array: superAttributes, copyItems: true) as? [UICollectionViewLayoutAttributes]
            else { return nil }
        return attributes.map({ self.transformLayoutAttributes($0) })
    }

    fileprivate func transformLayoutAttributes(_ attributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
        guard let collectionView = self.collectionView else { return attributes }
        let isHorizontal = (self.scrollDirection == .horizontal)

        let collectionCenter = isHorizontal ? collectionView.frame.size.width/2 : collectionView.frame.size.height/2
        let offset = isHorizontal ? collectionView.contentOffset.x : collectionView.contentOffset.y
        let normalizedCenter = (isHorizontal ? attributes.center.x : attributes.center.y) - offset

        let maxDistance = (isHorizontal ? self.itemSize.width : self.itemSize.height) + self.minimumLineSpacing
        let distance = min(abs(collectionCenter - normalizedCenter), maxDistance)
        let ratio = (maxDistance - distance)/maxDistance

        let alpha = ratio * (1 - self.sideItemAlpha) + self.sideItemAlpha
        let scale = ratio * (1 - self.sideItemScale) + self.sideItemScale
        attributes.alpha = alpha
        attributes.transform3D = CATransform3DScale(CATransform3DIdentity, scale, scale, 1)
        attributes.zIndex = Int(alpha * 10)

        return attributes
    }

    override open func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
        guard let collectionView = collectionView , !collectionView.isPagingEnabled,
            let layoutAttributes = self.layoutAttributesForElements(in: collectionView.bounds)
            else { return super.targetContentOffset(forProposedContentOffset: proposedContentOffset) }

        let isHorizontal = (self.scrollDirection == .horizontal)

        let midSide = (isHorizontal ? collectionView.bounds.size.width : collectionView.bounds.size.height) / 2
        let proposedContentOffsetCenterOrigin = (isHorizontal ? proposedContentOffset.x : proposedContentOffset.y) + midSide

        var targetContentOffset: CGPoint
        if isHorizontal {
            let closest = layoutAttributes.sorted { abs($0.center.x - proposedContentOffsetCenterOrigin) < abs($1.center.x - proposedContentOffsetCenterOrigin) }.first ?? UICollectionViewLayoutAttributes()
            targetContentOffset = CGPoint(x: floor(closest.center.x - midSide), y: proposedContentOffset.y)
        }
        else {
            let closest = layoutAttributes.sorted { abs($0.center.y - proposedContentOffsetCenterOrigin) < abs($1.center.y - proposedContentOffsetCenterOrigin) }.first ?? UICollectionViewLayoutAttributes()
            targetContentOffset = CGPoint(x: proposedContentOffset.x, y: floor(closest.center.y - midSide))
        }

        return targetContentOffset
    }
}

导入UIKit
公共枚举UpcarouselFlowLayoutPacingMode{
固定大小写（间距：CGFloat）
案例重叠（visibleOffset:CGFloat）
}
开放类UPCarouselFlowLayout:UICollectionViewFlowLayout{
fileprivate结构布局状态{
变量大小：CGSize
变量方向：UICollectionViewScrollDirection
func isEqual（uOtherState:LayoutState）->Bool{
返回self.size.equalTo（otherState.size）和&self.direction==otherState.direction
}
}
@IBInspectable open var sideItemScale:CGFloat=0.6
@IBInspectable open var sideItemAlpha:CGFloat=0.6
open var spacingMode=UPCAROUSELFLOWLAYOUTPACINGMODE.固定（间距：40）
fileprivate var state=LayoutState（大小：CGSize.zero，方向：。水平）
覆盖打开的func prepare（）{
超级准备
让currentState=LayoutState（大小：self.collectionView！.bounds.size，方向：self.scrollDirection）
if！self.state.isEqual（当前状态）{
self.setupCollectionView（）
self.updateLayout（）
self.state=当前状态
}
}
fileprivate func setupCollectionView（）{
guard let collectionView=self.collectionView else{return}
如果collectionView.decelerationRate！=UIScrollViewDecelerationRateFast{
collectionView.decelerationRate=UIScrollViewDecelerationRateFast
}
}
fileprivate func updateLayout（）{
guard let collectionView=self.collectionView else{return}
让collectionSize=collectionView.bounds.size
设isHorizontal=（self.scrollDirection==.horizontal）
让yInset=（collectionSize.height-self.itemSize.height）/2
让xInset=（collectionSize.width-self.itemSize.width）/2
self.sectionInset=UIEdgeInsetsMake（yInset，xInset，yInset，xInset）
let side=isHorizontal？self.itemSize.width:self.itemSize.height
设scaledItemOffset=（side-side*self.sideItemScale）/2
开关自间距模式{
案例。固定（让间距）：
self.minimumLineSpacing=间距-scaledItemOffset
案例重叠（让visibleOffset）：
设fullSizeSideItemOverlap=visibleOffset+ScaleEdItemOffset
让插图=水平？xInset:yInset
self.minimumlinespating=插入-全尺寸尺寸最小重叠
}
}
覆盖打开的函数应验证布局（forBoundsChange newBounds:CGRect）->Bool{
返回真值
}
是否覆盖打开的func layoutAttributesForElements（在rect:CGRect中）->[UICollectionViewLayoutAttributes]{
guard let superAttributes=super.layoutAttributesForElements（in:rect），
将attributes=NSArray（数组：SuperAttribute，copyItems:true）设为？[UICollectionViewLayoutAttribute]
else{return nil}
返回attributes.map（{self.transformLayoutAttribute（$0）}）
}
fileprivate func TransformLayoutAttribute（u属性：UICollectionViewLayoutAttribute）->UICollectionViewLayoutAttribute{
guard let collectionView=self.collectionView else{return attributes}
设isHorizontal=（self.scrollDirection==.horizontal）
让collectionCenter=isHorizontal？collectionView.frame.size.width/2:collectionView.frame.size.height/2
让offset=isHorizontal？collectionView.contentOffset.x:collectionView.contentOffset.y
设normalizedCenter=（isHorizontal？attributes.center.x:attributes.center.y）-偏移量
设maxDistance=（isHorizontal？self.itemSize.width:self.itemSize.height）+self.minimumlinespace
让距离=最小值（abs（采集中心-标准化中心），最大距离）
let比率=（最大距离-距离）/最大距离
设alpha=比率*（1-self.sideItemAlpha）+self.sideItemAlpha
设比例=比率*（1-self.sideItemScale）+self.sideItemScale
attributes.alpha=alpha
attributes.transform3D=CATTransferrM3DScale（CATTransferrM3DidEntity，scale，scale，1）
attributes.zIndex=Int（alpha*10）
返回属性
}
覆盖开放函数targetContentOffset（forProposedContentOffset proposedContentOffset:CGPoint，使用CrollingVelocity:CGPoint）->CGPoint{
guard let collectionView=collectionView，！collection
import UIKit


public enum UPCarouselFlowLayoutSpacingMode {
    case fixed(spacing: CGFloat)
    case overlap(visibleOffset: CGFloat)
}


open class UPCarouselFlowLayout: UICollectionViewFlowLayout {

    fileprivate struct LayoutState {
        var size: CGSize
        var direction: UICollectionViewScrollDirection
        func isEqual(_ otherState: LayoutState) -> Bool {
            return self.size.equalTo(otherState.size) && self.direction == otherState.direction
        }
    }

    @IBInspectable open var sideItemScale: CGFloat = 0.6
    @IBInspectable open var sideItemAlpha: CGFloat = 0.6
    open var spacingMode = UPCarouselFlowLayoutSpacingMode.fixed(spacing: 40)

    fileprivate var state = LayoutState(size: CGSize.zero, direction: .horizontal)


    override open func prepare() {
        super.prepare()

        let currentState = LayoutState(size: self.collectionView!.bounds.size, direction: self.scrollDirection)

        if !self.state.isEqual(currentState) {
            self.setupCollectionView()
            self.updateLayout()
            self.state = currentState
        }
    }

    fileprivate func setupCollectionView() {
        guard let collectionView = self.collectionView else { return }
        if collectionView.decelerationRate != UIScrollViewDecelerationRateFast {
            collectionView.decelerationRate = UIScrollViewDecelerationRateFast
        }
    }

    fileprivate func updateLayout() {
        guard let collectionView = self.collectionView else { return }

        let collectionSize = collectionView.bounds.size
        let isHorizontal = (self.scrollDirection == .horizontal)

        let yInset = (collectionSize.height - self.itemSize.height) / 2
        let xInset = (collectionSize.width - self.itemSize.width) / 2
        self.sectionInset = UIEdgeInsetsMake(yInset, xInset, yInset, xInset)

        let side = isHorizontal ? self.itemSize.width : self.itemSize.height
        let scaledItemOffset =  (side - side*self.sideItemScale) / 2
        switch self.spacingMode {
        case .fixed(let spacing):
            self.minimumLineSpacing = spacing - scaledItemOffset
        case .overlap(let visibleOffset):
            let fullSizeSideItemOverlap = visibleOffset + scaledItemOffset
            let inset = isHorizontal ? xInset : yInset
            self.minimumLineSpacing = inset - fullSizeSideItemOverlap
        }
    }

    override open func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true
    }

    override open func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let superAttributes = super.layoutAttributesForElements(in: rect),
            let attributes = NSArray(array: superAttributes, copyItems: true) as? [UICollectionViewLayoutAttributes]
            else { return nil }
        return attributes.map({ self.transformLayoutAttributes($0) })
    }

    fileprivate func transformLayoutAttributes(_ attributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
        guard let collectionView = self.collectionView else { return attributes }
        let isHorizontal = (self.scrollDirection == .horizontal)

        let collectionCenter = isHorizontal ? collectionView.frame.size.width/2 : collectionView.frame.size.height/2
        let offset = isHorizontal ? collectionView.contentOffset.x : collectionView.contentOffset.y
        let normalizedCenter = (isHorizontal ? attributes.center.x : attributes.center.y) - offset

        let maxDistance = (isHorizontal ? self.itemSize.width : self.itemSize.height) + self.minimumLineSpacing
        let distance = min(abs(collectionCenter - normalizedCenter), maxDistance)
        let ratio = (maxDistance - distance)/maxDistance

        let alpha = ratio * (1 - self.sideItemAlpha) + self.sideItemAlpha
        let scale = ratio * (1 - self.sideItemScale) + self.sideItemScale
        attributes.alpha = alpha
        attributes.transform3D = CATransform3DScale(CATransform3DIdentity, scale, scale, 1)
        attributes.zIndex = Int(alpha * 10)

        return attributes
    }

    override open func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
        guard let collectionView = collectionView , !collectionView.isPagingEnabled,
            let layoutAttributes = self.layoutAttributesForElements(in: collectionView.bounds)
            else { return super.targetContentOffset(forProposedContentOffset: proposedContentOffset) }

        let isHorizontal = (self.scrollDirection == .horizontal)

        let midSide = (isHorizontal ? collectionView.bounds.size.width : collectionView.bounds.size.height) / 2
        let proposedContentOffsetCenterOrigin = (isHorizontal ? proposedContentOffset.x : proposedContentOffset.y) + midSide

        var targetContentOffset: CGPoint
        if isHorizontal {
            let closest = layoutAttributes.sorted { abs($0.center.x - proposedContentOffsetCenterOrigin) < abs($1.center.x - proposedContentOffsetCenterOrigin) }.first ?? UICollectionViewLayoutAttributes()
            targetContentOffset = CGPoint(x: floor(closest.center.x - midSide), y: proposedContentOffset.y)
        }
        else {
            let closest = layoutAttributes.sorted { abs($0.center.y - proposedContentOffsetCenterOrigin) < abs($1.center.y - proposedContentOffsetCenterOrigin) }.first ?? UICollectionViewLayoutAttributes()
            targetContentOffset = CGPoint(x: proposedContentOffset.x, y: floor(closest.center.y - midSide))
        }

        return targetContentOffset
    }
}