FoldingCell与UICollectionView:跨组件折叠效果实现

FoldingCell与UICollectionView:跨组件折叠效果实现

【免费下载链接】folding-cell :octocat: 📃 FoldingCell is an expanding content cell with animation made by @Ramotion 【免费下载链接】folding-cell 项目地址: https://gitcode.com/gh_mirrors/fo/folding-cell

你是否在开发iOS应用时遇到过需要展示大量信息却又不想占据太多屏幕空间的困境?用户常常需要在有限的界面中快速获取关键信息,同时又希望能方便地查看详情。传统的展开/收起功能往往显得生硬,缺乏吸引力。本文将介绍如何利用FoldingCell与UICollectionView结合,实现流畅优雅的跨组件折叠效果,让你的应用界面既简洁又富有交互性。

读完本文后,你将能够:

  • 理解FoldingCell的核心原理和使用方法
  • 掌握在UICollectionView中集成折叠效果的技巧
  • 解决跨组件动画同步的常见问题
  • 优化折叠动画性能,提升用户体验

FoldingCell简介

FoldingCell是由Ramotion开发的一个开源iOS组件,它提供了一种优雅的单元格折叠展开动画效果。不同于普通的单元格展开,FoldingCell通过模拟纸张折叠的动画,让内容的展示和隐藏过程更加生动有趣。

FoldingCell效果展示

FoldingCell的核心文件是FoldingCell.swift,它定义了FoldingCell类及其相关组件。该组件的主要特点包括:

  • 平滑的折叠展开动画效果
  • 高度可定制的折叠参数
  • 支持Storyboard和纯代码两种集成方式
  • 兼容iOS 8.0及以上版本

环境准备与安装

要在项目中使用FoldingCell,首先需要确保你的开发环境满足以下要求:

  • iOS 8.0+
  • Xcode 10.2+
  • Swift 5.0+

FoldingCell提供了多种安装方式,你可以根据项目需求选择最合适的方式:

使用CocoaPods安装

在Podfile中添加以下代码:

pod 'FoldingCell'

然后在终端中执行pod install命令。

使用Carthage安装

在Cartfile中添加以下代码:

github "Ramotion/folding-cell"

然后执行carthage update命令。

使用Swift Package Manager安装

在Package.swift文件中添加以下依赖:

dependencies: [
    .package(url: "https://gitcode.com/gh_mirrors/fo/folding-cell.git", from: "5.0.2")
]

手动安装

最简单的方式是直接将FoldingCell.swift文件添加到你的项目中。

FoldingCell核心原理

FoldingCell的实现基于UIKit的核心动画框架,通过对UIView的layer进行3D变换来模拟折叠效果。其核心原理可以概括为以下几点:

  1. 双层视图结构:每个FoldingCell包含前景视图(foregroundView)和容器视图(containerView)。前景视图用于展示折叠状态下的内容,容器视图则包含展开后的完整内容。

  2. 3D变换:通过修改CALayer的transform属性,特别是m34值来创建透视效果,使折叠动画更具立体感。

  3. 动画序列:将折叠过程分解为多个动画步骤,通过CAAnimationGroup协调执行,实现平滑的折叠过渡效果。

下面是FoldingCell类的核心属性定义:

open class FoldingCell: UITableViewCell {
    @objc open var isUnfolded = false
    
    /// UIView is displayed when cell open
    @IBOutlet open var containerView: UIView!
    @IBOutlet open var containerViewTop: NSLayoutConstraint!
    
    /// UIView which display when cell close
    @IBOutlet open var foregroundView: RotatedView!
    @IBOutlet open var foregroundViewTop: NSLayoutConstraint!
    
    /// The number of folding elements. Default 2
    @IBInspectable open var itemCount: NSInteger = 2
    
    /// The color of the back cell
    @IBInspectable open var backViewColor: UIColor = UIColor.brown
}

在UICollectionView中集成FoldingCell

虽然FoldingCell最初是为UITableView设计的,但通过一些调整,我们也可以在UICollectionView中实现类似的折叠效果。下面将详细介绍实现步骤。

创建自定义CollectionViewCell

首先,我们需要创建一个继承自UICollectionViewCell的自定义单元格,并集成FoldingCell的功能。创建一个新的Swift文件,命名为FoldingCollectionViewCell.swift,添加以下代码:

import UIKit

class FoldingCollectionViewCell: UICollectionViewCell {
    // FoldingCell相关属性
    var isUnfolded = false
    var containerView: UIView!
    var foregroundView: RotatedView!
    var itemCount: NSInteger = 2
    var backViewColor: UIColor = UIColor.brown
    
    // 其他自定义属性
    // ...
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    
    func commonInit() {
        // 初始化视图和约束
        setupViews()
        setupConstraints()
    }
    
    func setupViews() {
        // 创建前景视图和容器视图
        foregroundView = RotatedView()
        foregroundView.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(foregroundView)
        
        containerView = UIView()
        containerView.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(containerView)
        
        // 设置初始样式
        foregroundView.backgroundColor = .white
        containerView.backgroundColor = .white
        foregroundView.layer.cornerRadius = 8
        containerView.layer.cornerRadius = 8
        foregroundView.clipsToBounds = true
        containerView.clipsToBounds = true
    }
    
    func setupConstraints() {
        // 添加视图约束
        NSLayoutConstraint.activate([
            foregroundView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 8),
            foregroundView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -8),
            foregroundView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 8),
            foregroundView.heightAnchor.constraint(equalToConstant: 100),
            
            containerView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 8),
            containerView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -8),
            containerView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 8),
            containerView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -8)
        ])
    }
    
    // FoldingCell核心方法将在后续步骤中实现
}

实现折叠动画逻辑

接下来,我们需要将FoldingCell的核心动画逻辑移植到自定义的CollectionViewCell中。我们可以从FoldingCell.swift中借鉴关键代码,实现折叠展开功能。

首先,添加RotatedView类,这是实现3D折叠效果的关键:

class RotatedView: UIView {
    var hiddenAfterAnimation = false
    var backView: RotatedView?
    
    func addBackView(_ height: CGFloat, color: UIColor) {
        let view = RotatedView(frame: CGRect.zero)
        view.backgroundColor = color
        view.layer.anchorPoint = CGPoint(x: 0.5, y: 1)
        view.layer.transform = view.transform3d()
        view.translatesAutoresizingMaskIntoConstraints = false
        self.addSubview(view)
        backView = view
        
        view.addConstraint(NSLayoutConstraint(item: view, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .height, multiplier: 1, constant: height))
        
        self.addConstraints([
            NSLayoutConstraint(item: view, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1, constant: self.bounds.size.height - height + height / 2),
            NSLayoutConstraint(item: view, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1, constant: 0),
            NSLayoutConstraint(item: view, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: 0),
            ])
    }
    
    func transform3d() -> CATransform3D {
        var transform = CATransform3DIdentity
        transform.m34 = 2.5 / -2000
        return transform
    }
    
    func foldingAnimation(timing: String, from: CGFloat, to: CGFloat, duration: TimeInterval, delay: TimeInterval, hidden: Bool) {
        let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation.x")
        rotateAnimation.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName(rawValue: timing))
        rotateAnimation.fromValue = from
        rotateAnimation.toValue = to
        rotateAnimation.duration = duration
        rotateAnimation.delegate = self
        rotateAnimation.fillMode = CAMediaTimingFillMode.forwards
        rotateAnimation.isRemovedOnCompletion = false
        rotateAnimation.beginTime = CACurrentMediaTime() + delay
        
        self.hiddenAfterAnimation = hidden
        
        self.layer.add(rotateAnimation, forKey: "rotation.x")
    }
}

extension RotatedView: CAAnimationDelegate {
    func animationDidStart(_ anim: CAAnimation) {
        self.layer.shouldRasterize = true
        self.alpha = 1
    }
    
    func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
        if hiddenAfterAnimation {
            self.alpha = 0
        }
        self.layer.removeAllAnimations()
        self.layer.shouldRasterize = false
        var transform = CATransform3DIdentity
        transform.m34 = 2.5 / -2000
        self.layer.transform = transform
    }
}

然后,在FoldingCollectionViewCell中实现折叠展开方法:

// 添加到FoldingCollectionViewCell类中
var animationView: UIView?
var animationItemViews: [RotatedView]?

func commonInit() {
    configureDefaultState()
    createAnimationView()
}

private func configureDefaultState() {
    containerView.alpha = 0
    foregroundView.layer.anchorPoint = CGPoint(x: 0.5, y: 1)
    foregroundView.layer.transform = foregroundView.transform3d()
    contentView.bringSubviewToFront(foregroundView)
}

private func createAnimationView() {
    animationView = UIView(frame: containerView.frame)
    animationView?.layer.cornerRadius = foregroundView.layer.cornerRadius
    animationView?.backgroundColor = .clear
    animationView?.translatesAutoresizingMaskIntoConstraints = false
    animationView?.alpha = 0
    
    guard let animationView = self.animationView else { return }
    
    self.contentView.addSubview(animationView)
    
    // 添加约束
    NSLayoutConstraint.activate([
        animationView.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
        animationView.trailingAnchor.constraint(equalTo: containerView.trailingAnchor),
        animationView.topAnchor.constraint(equalTo: containerView.topAnchor),
        animationView.bottomAnchor.constraint(equalTo: containerView.bottomAnchor)
    ])
}

func transform3d() -> CATransform3D {
    var transform = CATransform3DIdentity
    transform.m34 = 2.5 / -2000
    return transform
}

func unfold(_ value: Bool, animated: Bool = true, completion: (() -> Void)? = nil) {
    if animated {
        value ? openAnimation(completion) : closeAnimation(completion)
    } else {
        foregroundView.alpha = value ? 0 : 1
        containerView.alpha = value ? 1 : 0
        isUnfolded = value
    }
}

func openAnimation(_ completion: (() -> Void)?) {
    isUnfolded = true
    removeImageItemsFromAnimationView()
    addImageItemsToAnimationView()
    
    animationView?.alpha = 1
    containerView.alpha = 0
    
    let durations = durationSequence(.open)
    
    var delay: TimeInterval = 0
    var timing = "easeIn"
    var from: CGFloat = 0.0
    var to: CGFloat = -CGFloat.pi / 2
    var hidden = true
    configureAnimationItems(.open)
    
    guard let animationItemViews = self.animationItemViews else {
        return
    }
    
    for index in 0 ..< animationItemViews.count {
        let animatedView = animationItemViews[index]
        
        animatedView.foldingAnimation(timing: timing, from: from, to: to, duration: durations[index], delay: delay, hidden: hidden)
        
        from = from == 0.0 ? CGFloat.pi / 2 : 0.0
        to = to == 0.0 ? -CGFloat.pi / 2 : 0.0
        timing = timing == "easeIn" ? "easeOut" : "easeIn"
        hidden = !hidden
        delay += durations[index]
    }
    
    DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
        self.animationView?.alpha = 0
        self.containerView.alpha = 1
        completion?()
    }
}

func closeAnimation(_ completion: (() -> Void)?) {
    isUnfolded = false
    removeImageItemsFromAnimationView()
    addImageItemsToAnimationView()
    
    guard let animationItemViews = self.animationItemViews else {
        return
    }
    
    animationView?.alpha = 1
    containerView.alpha = 0
    
    let durations: [TimeInterval] = durationSequence(.close).reversed()
    
    var delay: TimeInterval = 0
    var timing = "easeIn"
    var from: CGFloat = 0.0
    var to: CGFloat = CGFloat.pi / 2
    var hidden = true
    configureAnimationItems(.close)
    
    for index in 0 ..< animationItemViews.count {
        let animatedView = animationItemViews.reversed()[index]
        
        animatedView.foldingAnimation(timing: timing, from: from, to: to, duration: durations[index], delay: delay, hidden: hidden)
        
        to = to == 0.0 ? CGFloat.pi / 2 : 0.0
        from = from == 0.0 ? -CGFloat.pi / 2 : 0.0
        timing = timing == "easeIn" ? "easeOut" : "easeIn"
        hidden = !hidden
        delay += durations[index]
    }
    
    DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
        self.animationView?.alpha = 0
        self.foregroundView.alpha = 1
        completion?()
    }
}

private func addImageItemsToAnimationView() {
    containerView.alpha = 1
    let containerViewSize = containerView.bounds.size
    let foregroundViewSize = foregroundView.bounds.size
    
    // 添加第一个视图
    var image = containerView.takeSnapshot(CGRect(x: 0, y: 0, width: containerViewSize.width, height: foregroundViewSize.height))
    var imageView = UIImageView(image: image)
    imageView.tag = 0
    imageView.layer.cornerRadius = foregroundView.layer.cornerRadius
    animationView?.addSubview(imageView)
    
    // 添加其他视图
    let itemHeight = (containerViewSize.height - 2 * foregroundViewSize.height) / CGFloat(itemCount - 2)
    
    var yPosition = foregroundViewSize.height
    var tag = 1
    for _ in 1 ..< itemCount {
        let height = tag == 1 ? foregroundViewSize.height : itemHeight
        image = containerView.takeSnapshot(CGRect(x: 0, y: yPosition, width: containerViewSize.width, height: height))
        
        imageView = UIImageView(image: image)
        let rotatedView = RotatedView(frame: CGRect(x: 0, y: yPosition, width: containerViewSize.width, height: height))
        rotatedView.tag = tag
        rotatedView.layer.anchorPoint = CGPoint(x: 0.5, y: 0)
        rotatedView.layer.transform = rotatedView.transform3d()
        
        rotatedView.addSubview(imageView)
        animationView?.addSubview(rotatedView)
        
        yPosition += height
        tag += 1
    }
    
    containerView.alpha = 0
    
    // 添加背面视图
    if let animationView = self.animationView {
        var previuosView: RotatedView?
        for case let container as RotatedView in animationView.subviews.sorted(by: { $0.tag < $1.tag }) where container.tag > 0 {
            previuosView?.addBackView(container.bounds.size.height, color: backViewColor)
            previuosView = container
        }
    }
    animationItemViews = createAnimationItemView()
}

private func createAnimationItemView() -> [RotatedView] {
    var items = [RotatedView]()
    items.append(foregroundView)
    var rotatedViews = [RotatedView]()
    
    animationView?.subviews
        .compactMap({ $0 as? RotatedView })
        .sorted(by: { $0.tag < $1.tag })
        .forEach { itemView in
            rotatedViews.append(itemView)
            if let backView = itemView.backView {
                rotatedViews.append(backView)
            }
    }
    
    items.append(contentsOf: rotatedViews)
    return items
}

private func removeImageItemsFromAnimationView() {
    animationView?.subviews.forEach({ $0.removeFromSuperview() })
}

private func configureAnimationItems(_ animationType: AnimationType) {
    if animationType == .open {
        animationView?.subviews
            .compactMap { $0 as? RotatedView }
            .forEach { $0.alpha = 0 }
    } else {
        animationView?.subviews
            .compactMap { $0 as? RotatedView }
            .forEach {
                $0.alpha = 1
                $0.backView?.alpha = 0
        }
    }
}

enum AnimationType {
    case open
    case close
}

func durationSequence(_ type: AnimationType) -> [TimeInterval] {
    var durations = [TimeInterval]()
    for i in 0 ..< itemCount - 1 {
        let duration = animationDuration(i, type: type)
        durations.append(duration / 2.0)
        durations.append(duration / 2.0)
    }
    return durations
}

func animationDuration(_ itemIndex: Int, type: AnimationType) -> TimeInterval {
    let durations = [0.33, 0.26, 0.26]
    if itemIndex < durations.count {
        return durations[itemIndex]
    }
    return 0.26
}

最后,添加UIView的截图扩展方法:

extension UIView {
    func takeSnapshot(_ frame: CGRect) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(frame.size, false, 0)
        
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        context.translateBy(x: -frame.origin.x, y: -frame.origin.y)
        
        layer.render(in: context)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image
    }
    
    func transform3d() -> CATransform3D {
        var transform = CATransform3DIdentity
        transform.m34 = 2.5 / -2000
        return transform
    }
}

在UICollectionView中使用FoldingCell

现在,我们可以在UICollectionView中使用自定义的FoldingCollectionViewCell了。首先,在ViewController中设置CollectionView:

class FoldingCollectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    var collectionView: UICollectionView!
    var cellHeights = [CGFloat]()
    let cellCount = 10
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setupCollectionView()
        setupCellHeights()
    }
    
    private func setupCollectionView() {
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 16
        layout.minimumInteritemSpacing = 16
        layout.sectionInset = UIEdgeInsets(top: 16, left: 16, bottom: 16, right: 16)
        
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.backgroundColor = .lightGray
        collectionView.register(FoldingCollectionViewCell.self, forCellWithReuseIdentifier: "FoldingCell")
        view.addSubview(collectionView)
    }
    
    private func setupCellHeights() {
        for _ in 0..<cellCount {
            cellHeights.append(120) // 默认高度
        }
    }
    
    // UICollectionViewDataSource方法
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return cellCount
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "FoldingCell", for: indexPath) as! FoldingCollectionViewCell
        
        // 配置单元格内容
        configureCell(cell, at: indexPath)
        
        return cell
    }
    
    private func configureCell(_ cell: FoldingCollectionViewCell, at indexPath: IndexPath) {
        // 清除之前的内容
        cell.foregroundView.subviews.forEach { $0.removeFromSuperview() }
        cell.containerView.subviews.forEach { $0.removeFromSuperview() }
        
        // 添加前景视图内容
        let titleLabel = UILabel(frame: CGRect(x: 16, y: 16, width: cell.foregroundView.bounds.width - 32, height: 20))
        titleLabel.text = "项目 \(indexPath.item + 1)"
        titleLabel.font = UIFont.boldSystemFont(ofSize: 16)
        cell.foregroundView.addSubview(titleLabel)
        
        let subtitleLabel = UILabel(frame: CGRect(x: 16, y: 42, width: cell.foregroundView.bounds.width - 32, height: 40))
        subtitleLabel.text = "点击查看详情"
        subtitleLabel.font = UIFont.systemFont(ofSize: 14)
        subtitleLabel.textColor = .gray
        cell.foregroundView.addSubview(subtitleLabel)
        
        // 添加容器视图内容
        let detailLabel = UILabel(frame: CGRect(x: 16, y: 16, width: cell.containerView.bounds.width - 32, height: 100))
        detailLabel.text = "这是项目 \(indexPath.item + 1) 的详细信息。这里可以放置更多内容,包括描述、图片、按钮等。FoldingCell会优雅地展示和隐藏这些内容,提供流畅的用户体验。"
        detailLabel.numberOfLines = 0
        detailLabel.font = UIFont.systemFont(ofSize: 14)
        cell.containerView.addSubview(detailLabel)
        
        // 如果单元格是展开状态,显示容器视图
        if cell.isUnfolded {
            cell.containerView.alpha = 1
            cell.foregroundView.alpha = 0
        } else {
            cell.containerView.alpha = 0
            cell.foregroundView.alpha = 1
        }
    }
    
    // UICollectionViewDelegateFlowLayout方法
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let width = (view.bounds.width - 48) / 2 // 两列布局
        return CGSize(width: width, height: cellHeights[indexPath.item])
    }
    
    // 处理单元格点击
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard let cell = collectionView.cellForItem(at: indexPath) as? FoldingCollectionViewCell else { return }
        
        let isUnfolded = cell.isUnfolded
        let newHeight: CGFloat = isUnfolded ? 120 : 300
        
        // 更新高度
        cellHeights[indexPath.item] = newHeight
        
        // 执行折叠/展开动画
        cell.unfold(!isUnfolded, animated: true) {
            // 动画完成后刷新布局
            UIView.animate(withDuration: 0.3) {
                collectionView.performBatchUpdates(nil, completion: nil)
            }
        }
    }
}

跨组件动画同步

在实际项目中,你可能需要在多个组件之间保持动画同步,例如在UICollectionView和UITableView之间切换时保持折叠状态一致。以下是一些实现跨组件动画同步的技巧:

使用数据模型管理状态

创建一个专门的数据模型来管理每个项目的折叠状态,而不是依赖于视图组件本身:

struct ItemModel {
    let id: Int
    let title: String
    let detail: String
    var isExpanded: Bool = false
}

然后,在视图控制器中维护一个ItemModel数组,所有UI组件都基于这个数据模型来渲染:

var items: [ItemModel] = [
    ItemModel(id: 1, title: "项目 1", detail: "详细信息..."),
    ItemModel(id: 2, title: "项目 2", detail: "详细信息..."),
    // 更多项目...
]

实现共享动画控制器

创建一个单例动画控制器,统一管理所有折叠动画:

class AnimationController {
    static let shared = AnimationController()
    
    func animateFolding(cell: FoldingCollectionViewCell, isUnfolding: Bool, completion: (() -> Void)?) {
        // 统一的动画逻辑
        cell.unfold(isUnfolding, animated: true, completion: completion)
    }
}

使用通知中心同步状态

当一个组件中的折叠状态发生变化时,通过NotificationCenter通知其他组件:

// 发送通知
NotificationCenter.default.post(name: NSNotification.Name("ItemStateChanged"), object: nil, userInfo: ["id": item.id, "isExpanded": item.isExpanded])

// 接收通知
NotificationCenter.default.addObserver(self, selector: #selector(itemStateChanged(_:)), name: NSNotification.Name("ItemStateChanged"), object: nil)

@objc func itemStateChanged(_ notification: Notification) {
    guard let userInfo = notification.userInfo,
          let id = userInfo["id"] as? Int,
          let isExpanded = userInfo["isExpanded"] as? Bool else { return }
    
    // 更新对应项目的状态
    if let index = items.firstIndex(where: { $0.id == id }) {
        items[index].isExpanded = isExpanded
        collectionView.reloadItems(at: [IndexPath(item: index, section: 0)])
    }
}

动画优化与性能调优

虽然FoldingCell提供了精美的动画效果,但在处理大量数据或复杂视图时,可能会遇到性能问题。以下是一些优化建议:

使用缓存减少计算量

FoldingCell在动画过程中需要截取视图快照,这是一个相对耗时的操作。可以通过缓存快照来提高性能:

var snapshotCache = [Int: UIImage]()

func getCachedSnapshot(for index: Int, view: UIView) -> UIImage {
    if let cachedImage = snapshotCache[index] {
        return cachedImage
    }
    
    let snapshot = view.takeSnapshot(view.bounds)
    snapshotCache[index] = snapshot
    return snapshot!
}

减少动画视图数量

FoldingCell的itemCount属性控制折叠的段数,段数越多,动画越复杂,性能消耗也越大。在不影响视觉效果的前提下,尽量减少itemCount的值。

使用shouldRasterize提高渲染性能

在动画过程中,可以开启图层光栅化来提高性能:

view.layer.shouldRasterize = true
view.layer.rasterizationScale = UIScreen.main.scale

注意在动画结束后关闭光栅化,避免内存占用过高。

异步加载内容

如果容器视图中包含复杂内容(如图片、WebView等),建议在折叠状态下异步加载这些内容,避免影响动画流畅度。

常见问题解决方案

在使用FoldingCell的过程中,你可能会遇到一些常见问题。下面提供了这些问题的解决方案和示例。

问题1:动画过程中内容闪烁

这通常是由于视图层级或透明度设置不当导致的。解决方案是确保动画视图在正确的层级,并适当调整透明度。

解决方案图示

问题2:折叠状态与内容不匹配

这可能是由于约束设置不正确造成的。确保前景视图和容器视图的约束正确无误,特别是在使用Auto Layout时。

约束设置示例

正确的约束设置应该类似于:

约束设置示例

问题3:在CollectionView中动画不同步

这是因为UICollectionView的布局更新与FoldingCell的动画不同步导致的。解决方案是在动画完成后再更新布局:

cell.unfold(!isUnfolded, animated: true) {
    UIView.animate(withDuration: 0.3) {
        collectionView.performBatchUpdates(nil, completion: nil)
    }
}

总结与展望

通过本文的介绍,我们学习了如何使用FoldingCell组件,并将其与UICollectionView结合,实现跨组件的折叠效果。我们深入了解了FoldingCell的核心原理,掌握了在不同场景下集成和定制折叠动画的方法,并学习了如何优化动画性能和解决常见问题。

FoldingCell作为一个优秀的动画组件,不仅可以提升用户体验,还能为你的应用增添独特的视觉魅力。未来,你可以进一步扩展FoldingCell的功能,例如:

  • 添加手势控制,支持滑动折叠/展开
  • 实现横向折叠效果
  • 结合UIKit Dynamics创建更复杂的物理动画
  • 适配深色模式和动态字体

希望本文能帮助你在项目中实现出色的折叠动画效果,为用户带来更加流畅和愉悦的体验。

参考资源

【免费下载链接】folding-cell :octocat: 📃 FoldingCell is an expanding content cell with animation made by @Ramotion 【免费下载链接】folding-cell 项目地址: https://gitcode.com/gh_mirrors/fo/folding-cell

创作声明:本文部分内容由AI辅助生成(AIGC),仅供参考

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