54798ba578
- 给全部 78 个 Swift 源文件添加详细的中文注释（文件级、类级、方法级） - 删除 LegacyRDReaderController/ 死代码目录（16 文件 4592 行） - 根目录翻页容器文件移入 ReaderView/ 目录 - Resources/ 移入 EPUBCore/Resources/（与使用者归属一致） - RDEPUBTextIndexTable.swift 移入 EPUBTextRendering/（消除反向依赖） - RDURLReaderController.swift 移入 EPUBUI/（入口控制器归入 UI 层） - 更新 podspec 资源路径
376 lines
15 KiB
Swift
376 lines
15 KiB
Swift
//
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// RDReaderFlowLayout.swift
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// RDReaderDemo
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//
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// Created by yangsq on 2021/8/6.
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//
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// 文件职责：自定义 UICollectionViewFlowLayout，支持阅读器的三种滚动布局模式。
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// 该文件实现了水平滚动（全屏宽 item + 分页）、垂直滚动（可变高度）和
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// 封面感知的双页布局（含封面页独占整屏逻辑）。
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//
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// 架构位置：RDReaderView 四层架构中第三层的布局组件，被 RDReaderView 持有和配置。
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//
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import UIKit
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/// 流式布局数据源协议
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/// 提供垂直滚动模式下各页面的高度信息
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public protocol RDReaderFlowLayoutDataSoure: NSObjectProtocol {
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/// 返回垂直滚动模式下指定页的高度
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/// - Parameters:
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/// - flowLayout: 发起请求的布局对象
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/// - pageIndex: 页码索引
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/// - Returns: 该页的高度，nil 表示使用默认高度（collectionView.frame.height）
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func heigtOfVerticalScrollPage(flowLayout: RDReaderFlowLayout, pageIndex: Int) -> CGFloat?
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}
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/// 流式布局代理协议
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/// 当当前可见页码变化时通知外部
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@objc public protocol RDReaderFlowLayoutDelegate: NSObjectProtocol {
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/// 页码变化回调
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/// - Parameters:
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/// - flowLayout: 发起回调的布局对象
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/// - pageIndex: 当前页码
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func pageNum(flowLayout: RDReaderFlowLayout, pageIndex: Int)
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}
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/// 自定义流式布局，支持阅读器的三种滚动布局模式：
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/// - horizontalScroll：水平滚动，每屏1项（竖屏）或2项（横屏双页），支持分页
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/// - verticalScroll：垂直滚动，全宽项目，支持可变高度
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///
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/// 通过 ``displayType`` 属性切换布局模式。
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/// 通过 ``isLandscapeDualPage`` 和 ``coverPageIndex`` 控制横屏双页和封面页逻辑。
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public class RDReaderFlowLayout: UICollectionViewFlowLayout {
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/// 布局模式，切换时自动使布局失效并重新计算
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var displayType: RDReaderView.DisplayType = .horizontalScroll {
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didSet {
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invalidateLayout()
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}
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}
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/// 是否启用横屏双页模式
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/// 启用后水平滚动模式下每屏显示两项（各占半屏宽度）
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var isLandscapeDualPage: Bool = false {
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didSet {
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if oldValue != isLandscapeDualPage {
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invalidateLayout()
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}
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}
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}
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/// 封面页索引
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/// 设置后封面页独占整屏，后续页面两两配对各占半屏
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var coverPageIndex: Int? = nil {
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didSet {
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if oldValue != coverPageIndex {
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invalidateLayout()
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}
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}
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}
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/// 上一次 prepare 时的 bounds 尺寸，用于检测尺寸变化
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private var lastPreparedBoundsSize: CGSize = .zero
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/// 每屏显示的页数
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/// 仅在水平滚动+横屏双页模式下返回2，其他情况返回1
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var pagesPerScreen: Int {
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guard isLandscapeDualPage else { return 1 }
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switch displayType {
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case .horizontalScroll:
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if let cv = collectionView, cv.bounds.width > cv.bounds.height {
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return 2
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}
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return 1
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default:
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return 1
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}
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}
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/// 流式布局数据源，提供垂直滚动模式的页面高度
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weak var dataSource: RDReaderFlowLayoutDataSoure? = nil
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/// 流式布局代理，接收页码变化通知
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weak var delegate: RDReaderFlowLayoutDelegate? = nil
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/// 是否在双页模式下有封面页独占
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private var hasCoverPageInDualMode: Bool {
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return pagesPerScreen > 1 && coverPageIndex != nil
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}
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/// 封面感知的帧计算：根据索引计算 item 的 frame
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/// 封面页独占整屏，后续页面两两配对各占半屏
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/// - Parameters:
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/// - index: item 索引
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/// - screenWidth: 屏幕宽度
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/// - halfWidth: 半屏宽度
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/// - height: 屏幕高度
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/// - Returns: 该 item 的 frame
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private func coverAwareFrame(for index: Int, screenWidth: CGFloat, halfWidth: CGFloat, height: CGFloat) -> CGRect {
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guard let coverIndex = coverPageIndex else {
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let pairIdx = index / 2
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let side = index % 2
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let x = CGFloat(pairIdx) * screenWidth + CGFloat(side) * halfWidth
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return CGRect(x: x, y: 0, width: halfWidth, height: height)
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}
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if index == coverIndex {
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let screensBeforeCover = coverIndex / 2
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let x = CGFloat(screensBeforeCover) * screenWidth
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return CGRect(x: x, y: 0, width: screenWidth, height: height)
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}
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let adjustedIndex = index - (coverIndex + 1)
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let pairIdx = adjustedIndex / 2
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let side = adjustedIndex % 2
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let coverScreens = coverIndex / 2 + 1
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let x = CGFloat(coverScreens + pairIdx) * screenWidth + CGFloat(side) * halfWidth
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return CGRect(x: x, y: 0, width: halfWidth, height: height)
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}
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/// 封面感知的屏幕起始索引计算：根据滚动偏移量计算当前屏幕的第一个 item 索引
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/// - Parameters:
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/// - offset: 当前滚动偏移量
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/// - screenWidth: 屏幕宽度
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/// - Returns: 当前屏幕第一个 item 的索引
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private func coverAwareStartIndex(for offset: CGFloat, screenWidth: CGFloat) -> Int {
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let pps = pagesPerScreen
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guard let coverIdx = coverPageIndex, hasCoverPageInDualMode else {
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let screenIndex = Int((offset / screenWidth).rounded(.down))
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return screenIndex * pps
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}
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let coverScreens = coverIdx / 2 + 1
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let coverEnd = CGFloat(coverScreens) * screenWidth
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if offset < coverEnd {
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let screenIdx = Int((offset / screenWidth).rounded(.down))
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return screenIdx >= coverIdx / 2 ? coverIdx : screenIdx * pps
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} else {
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let pairIdx = Int(((offset - coverEnd) / screenWidth).rounded(.down))
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return coverIdx + 1 + pairIdx * 2
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}
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}
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/// 当前可见的页码，值变化时通过 delegate 通知外部
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private var currentPage: Int = 0 {
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didSet {
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if let delegate = delegate, delegate.responds(to: #selector(RDReaderFlowLayoutDelegate.pageNum(flowLayout:pageIndex:))), currentPage != oldValue, currentPage >= 0 {
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delegate.pageNum(flowLayout: self, pageIndex: currentPage)
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}
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}
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}
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/// 初始化方法
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/// - Parameter displayType: 初始布局模式
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init(displayType: RDReaderView.DisplayType) {
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self.displayType = displayType
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super.init()
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}
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/// 布局准备阶段，配置 item 尺寸、滚动方向和分页行为
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public override func prepare() {
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super.prepare()
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guard let collectionView = self.collectionView else {
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return
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}
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guard collectionView.frame.width > 0, collectionView.frame.height > 0 else {
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return
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}
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lastPreparedBoundsSize = collectionView.bounds.size
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if #available(iOS 11.0, *) {
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collectionView.contentInsetAdjustmentBehavior = .never
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} else {
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collectionView.ss_superViewController?.automaticallyAdjustsScrollViewInsets = false
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}
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collectionView.showsVerticalScrollIndicator = false
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collectionView.showsHorizontalScrollIndicator = false
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minimumLineSpacing = 0
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minimumInteritemSpacing = 0
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switch self.displayType {
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case .horizontalScroll:
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scrollDirection = .horizontal
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let columns = CGFloat(pagesPerScreen)
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itemSize = CGSize(width: collectionView.frame.width / columns, height: collectionView.frame.height)
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collectionView.isPagingEnabled = true
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case .verticalScroll:
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itemSize = CGSize(width: collectionView.frame.width, height: collectionView.frame.height)
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scrollDirection = .vertical
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collectionView.isPagingEnabled = false
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collectionView.showsVerticalScrollIndicator = true
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default: break
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}
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}
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/// 判断 bounds 变化是否需要使布局失效
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/// 尺寸变化时总是返回 true，布局模式变化也返回 true
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public override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
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if newBounds.size != lastPreparedBoundsSize {
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return true
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}
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switch displayType {
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case .verticalScroll:
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return true
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case .horizontalScroll:
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return true
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default:
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return false
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}
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}
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/// 计算 collectionView 的总内容尺寸
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/// 垂直滚动模式：累加所有页面高度
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/// 封面双页模式：封面占一屏 + 后续页面按两两配对计算屏幕数
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public override var collectionViewContentSize: CGSize {
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var size = super.collectionViewContentSize
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guard let collectionView = collectionView else {
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return size
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}
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if displayType == .verticalScroll {
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let totalHeight = [Int](0..<collectionView.numberOfItems(inSection: 0)).reduce(0.0, { result, num in
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result + (dataSource?.heigtOfVerticalScrollPage(flowLayout: self, pageIndex: num) ?? collectionView.frame.height)
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})
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size.height = totalHeight
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}
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if hasCoverPageInDualMode, displayType == .horizontalScroll {
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let totalItems = collectionView.numberOfItems(inSection: 0)
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let screenWidth = collectionView.frame.width
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let remainingItems = max(0, totalItems - 1)
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let pairedScreens = (remainingItems + 1) / 2
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size.width = screenWidth * CGFloat(1 + pairedScreens)
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}
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return size
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}
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/// 计算指定矩形区域内的布局属性
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/// 垂直滚动模式：根据可变高度定位每个 item
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/// 水平滚动模式：根据当前偏移量计算当前页码，清除 cell 阴影
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public override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
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var attributes = super.layoutAttributesForElements(in: rect)
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guard let collectionView = collectionView else {
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return attributes
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}
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if self.displayType == .verticalScroll {
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let rowCount = collectionView.numberOfItems(inSection: 0)
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var totalHeight: CGFloat = 0
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for index in 0..<rowCount {
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totalHeight += dataSource?.heigtOfVerticalScrollPage(flowLayout: self, pageIndex: index) ?? collectionView.frame.height
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if totalHeight > collectionView.contentOffset.y {
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self.currentPage = index
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break
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}
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}
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(attributes ?? []).forEach({ attr in
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let indexPath = attr.indexPath
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let lastRow = max(0, indexPath.row - 1)
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let height = dataSource?.heigtOfVerticalScrollPage(flowLayout: self, pageIndex: indexPath.row) ?? collectionView.frame.height
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var lastTotalHeight: CGFloat = 0
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if indexPath.row > 0 {
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lastTotalHeight = [Int](0...lastRow).reduce(0.0) { result, row in
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result + (dataSource?.heigtOfVerticalScrollPage(flowLayout: self, pageIndex: row) ?? collectionView.frame.height)
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}
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}
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if let cell = collectionView.cellForItem(at: indexPath) {
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cell.layer.shadowOpacity = 0
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}
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attr.frame = CGRect(x: 0, y: lastTotalHeight, width: collectionView.frame.width, height: height)
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})
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}
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if self.displayType == .horizontalScroll {
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let pps = pagesPerScreen
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if hasCoverPageInDualMode {
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let screenWidth = collectionView.frame.width
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let halfWidth = screenWidth / 2.0
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let rows = collectionView.numberOfItems(inSection: 0)
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self.currentPage = coverAwareStartIndex(for: collectionView.contentOffset.x, screenWidth: screenWidth)
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var attrs = [UICollectionViewLayoutAttributes]()
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for index in 0..<rows {
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let frame = coverAwareFrame(for: index, screenWidth: screenWidth, halfWidth: halfWidth, height: collectionView.frame.height)
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guard frame.intersects(rect) else { continue }
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let indexPath = IndexPath(item: index, section: 0)
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let attr = UICollectionViewLayoutAttributes(forCellWith: indexPath)
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attr.frame = frame
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attrs.append(attr)
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if let cell = collectionView.cellForItem(at: indexPath) {
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cell.layer.shadowOpacity = 0
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}
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}
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attributes = attrs
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} else if pps > 1 {
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let currentPage = Int((collectionView.contentOffset.x / collectionView.frame.width).rounded(.down)) * pps
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self.currentPage = currentPage
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(attributes ?? []).forEach({ attr in
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if let cell = collectionView.cellForItem(at: attr.indexPath) {
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cell.layer.shadowOpacity = 0
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}
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})
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} else {
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let currentPage = Int((collectionView.contentOffset.x / collectionView.frame.width).rounded(.down))
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self.currentPage = currentPage
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(attributes ?? []).forEach({ attr in
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if let cell = collectionView.cellForItem(at: attr.indexPath) {
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cell.layer.shadowOpacity = 0
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}
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})
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}
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}
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return attributes
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}
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/// 根据页码计算对应的 contentOffset
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/// 用于跳转到指定页面时设置滚动位置
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/// - Parameter count: 目标页码
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/// - Returns: 对应的 contentOffset 坐标
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func currentContentOffset(count: Int) -> CGPoint {
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guard let collectionView = collectionView else {
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return .zero
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}
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guard collectionView.frame.width > 0, collectionView.frame.height > 0 else {
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return .zero
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}
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let safeCount = max(0, count)
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switch displayType {
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case .verticalScroll:
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guard safeCount > 0 else { return .zero }
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let totalHeight = [Int](0...(safeCount - 1)).reduce(0.0) { result, pageNum in
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result + (dataSource?.heigtOfVerticalScrollPage(flowLayout: self, pageIndex: pageNum) ?? collectionView.frame.height)
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}
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return CGPoint(x: 0, y: totalHeight)
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default:
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let pps = pagesPerScreen
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let screenWidth = collectionView.frame.width
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if hasCoverPageInDualMode, let coverIdx = coverPageIndex {
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if safeCount == coverIdx {
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let screensBeforeCover = coverIdx / 2
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return CGPoint(x: CGFloat(screensBeforeCover) * screenWidth, y: 0)
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}
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if safeCount < coverIdx {
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return CGPoint(x: CGFloat(safeCount / 2) * screenWidth, y: 0)
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}
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let coverScreens = coverIdx / 2 + 1
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let adjustedIndex = safeCount - (coverIdx + 1)
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let pairIndex = adjustedIndex / 2
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return CGPoint(x: CGFloat(coverScreens + pairIndex) * screenWidth, y: 0)
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} else if pps > 1 {
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let screenIndex = safeCount / pps
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return CGPoint(x: CGFloat(screenIndex) * screenWidth, y: 0)
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} else {
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return CGPoint(x: CGFloat(safeCount) * itemSize.width, y: 0)
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}
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}
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}
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required init?(coder: NSCoder) {
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fatalError("init(coder:) has not been implemented")
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}
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}
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