//
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// LanternView.swift
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// Lantern
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//
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// Created by JiongXing on 2019/11/14.
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// Copyright © 2021 Shenzhen Hive Box Technology Co.,Ltd All rights reserved.
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//
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import UIKit
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open class LanternView: UIView, UIScrollViewDelegate {
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/// 弱引用lantern
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open weak var lantern: Lantern?
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/// 询问当前数据总量
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open lazy var numberOfItems: () -> Int = { 0 }
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/// 返回可复用的Cell类。用户可根据index返回不同的类。本闭包将在每次复用Cell时实时调用。
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open lazy var cellClassAtIndex: (_ index: Int) -> LanternCell.Type = { _ in
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LanternImageCell.self
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}
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/// 刷新Cell数据。本闭包将在Cell完成位置布局后调用。
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open lazy var reloadCellAtIndex: (Lantern.ReloadCellContext) -> Void = { _ in }
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/// 自然滑动引起的页码改变时回调
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open lazy var didChangedPageIndex: (_ index: Int) -> Void = { _ in }
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/// Cell将显示
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open lazy var cellWillAppear: (LanternCell, Int) -> Void = { _, _ in }
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/// Cell将不显示
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open lazy var cellWillDisappear: (LanternCell, Int) -> Void = { _, _ in }
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/// Cell已显示
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open lazy var cellDidAppear: (LanternCell, Int) -> Void = { _, _ in }
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/// 滑动方向
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open var scrollDirection: Lantern.ScrollDirection = .horizontal
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/// 项间距
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open var itemSpacing: CGFloat = 30
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/// 当前页码。给本属性赋值不会触发`didChangedPageIndex`闭包。
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open var pageIndex = 0 {
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didSet {
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if pageIndex != oldValue {
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isPageIndexChanged = true
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}
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}
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}
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/// 页码是否已改变
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public var isPageIndexChanged = true
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/// 容器
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open lazy var scrollView: UIScrollView = {
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let sv = UIScrollView()
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sv.backgroundColor = .clear
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sv.showsVerticalScrollIndicator = false
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sv.showsHorizontalScrollIndicator = false
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sv.isPagingEnabled = true
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sv.isScrollEnabled = true
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sv.delegate = self
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if #available(iOS 11.0, *) {
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sv.contentInsetAdjustmentBehavior = .never
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}
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return sv
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}()
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/// 新增更多num之前的数据总量
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open var lastNumberOfItems: Int = 0
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/// 是否旋转
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var isRotating = false
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deinit {
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LanternLog.high("deinit - \(self.classForCoder)")
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}
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public convenience init() {
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self.init(frame: .zero)
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}
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public override init(frame: CGRect) {
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super.init(frame: frame)
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setup()
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}
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public required init?(coder: NSCoder) {
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super.init(coder: coder)
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setup()
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}
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open func setup() {
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backgroundColor = .clear
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addSubview(scrollView)
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}
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open override func layoutSubviews() {
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super.layoutSubviews()
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if scrollDirection == .horizontal {
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scrollView.frame = CGRect(x: 0, y: 0, width: bounds.width + itemSpacing, height: bounds.height)
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} else {
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scrollView.frame = CGRect(x: 0, y: 0, width: bounds.width, height: bounds.height + itemSpacing)
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}
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reloadData()
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}
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open func resetContentSize() {
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let maxIndex = CGFloat(numberOfItems())
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if scrollDirection == .horizontal {
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scrollView.contentSize = CGSize(width: scrollView.frame.width * maxIndex,
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height: scrollView.frame.height)
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} else {
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scrollView.contentSize = CGSize(width: scrollView.frame.width,
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height: scrollView.frame.height * maxIndex)
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}
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}
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/// 刷新数据，同时刷新Cell布局
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open func reloadData() {
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// 修正pageIndex，同步数据源的变更
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pageIndex = max(0, pageIndex)
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pageIndex = min(pageIndex, numberOfItems())
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resetContentSize()
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resetCells()
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layoutCells()
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reloadItems()
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refreshContentOffset()
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}
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/// 根据页码更新滑动位置
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open func refreshContentOffset() {
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// 针对无限新增图片数据，scrollView的contentOffset会偏移问题判断处理
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if pageIndex == lastNumberOfItems {
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return
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}
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if scrollDirection == .horizontal {
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scrollView.contentOffset = CGPoint(x: CGFloat(pageIndex) * scrollView.bounds.width, y: 0)
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} else {
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scrollView.contentOffset = CGPoint(x: 0, y: CGFloat(pageIndex) * scrollView.bounds.height)
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}
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}
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open func scrollViewDidScroll(_ scrollView: UIScrollView) {
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// 屏幕旋转时会触发本方法。此时不可更改pageIndex
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if isRotating {
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resetCells()
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layoutCells()
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reloadItems()
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isRotating = false
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return
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}
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if scrollDirection == .horizontal && scrollView.bounds.width > 0 {
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pageIndex = Int(round(scrollView.contentOffset.x / (scrollView.bounds.width)))
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} else if scrollDirection == .vertical && scrollView.bounds.height > 0 {
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pageIndex = Int(round(scrollView.contentOffset.y / (scrollView.bounds.height)))
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}
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if isPageIndexChanged {
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isPageIndexChanged = false
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resetCells()
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layoutCells()
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reloadItems()
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didChangedPageIndex(pageIndex)
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}
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}
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public func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
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if let cell = visibleCells[pageIndex] {
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cellDidAppear(cell, pageIndex)
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}
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}
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//
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// MARK: - 复用Cell
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//
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/// 显示中的Cell
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open var visibleCells = [Int: LanternCell]()
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/// 缓存中的Cell
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open var reusableCells = [String: [LanternCell]]()
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/// 入队
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private func enqueue(cell: LanternCell) {
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let name = String(describing: cell.classForCoder)
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if var array = reusableCells[name] {
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array.append(cell)
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reusableCells[name] = array
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} else {
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reusableCells[name] = [cell]
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}
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}
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/// 出队，没缓存则新建
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private func dequeue(cellType: LanternCell.Type, browser: Lantern) -> LanternCell {
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var cell: LanternCell
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let name = String(describing: cellType.classForCoder())
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if var array = reusableCells[name], array.count > 0 {
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LanternLog.middle("命中缓存！\(name)")
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cell = array.removeFirst()
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reusableCells[name] = array
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} else {
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LanternLog.middle("新建Cell! \(name)")
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cell = cellType.generate(with: browser)
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}
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return cell
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}
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/// 重置所有Cell的位置。更新 visibleCells 和 reusableCells
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open func resetCells() {
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guard let browser = lantern else {
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return
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}
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var removeFromVisibles = [Int]()
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for (index, cell) in visibleCells {
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if index == pageIndex {
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continue
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}
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cellWillDisappear(cell, index)
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cell.removeFromSuperview()
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enqueue(cell: cell)
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removeFromVisibles.append(index)
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}
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removeFromVisibles.forEach { visibleCells.removeValue(forKey: $0) }
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// 添加要显示的cell
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let itemsTotalCount = numberOfItems()
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for index in (pageIndex - 1)...(pageIndex + 1) {
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if index < 0 || index > itemsTotalCount - 1 {
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continue
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}
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if index == pageIndex && visibleCells[index] != nil {
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continue
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}
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let clazz = cellClassAtIndex(index)
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LanternLog.middle("Required class name: \(String(describing: clazz))")
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LanternLog.middle("index:\(index) 出列!")
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let cell = dequeue(cellType: clazz, browser: browser)
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visibleCells[index] = cell
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scrollView.addSubview(cell)
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}
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}
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/// 刷新所有显示中的Cell位置
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open func layoutCells() {
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let cellWidth = bounds.width
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let cellHeight = bounds.height
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for (index, cell) in visibleCells {
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if scrollDirection == .horizontal {
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cell.frame = CGRect(x: CGFloat(index) * (cellWidth + itemSpacing), y: 0, width: cellWidth, height: cellHeight)
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} else {
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cell.frame = CGRect(x: 0, y: CGFloat(index) * (cellHeight + itemSpacing), width: cellWidth, height: cellHeight)
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}
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}
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}
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/// 刷新所有Cell的数据
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open func reloadItems() {
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visibleCells.forEach { [weak self] index, cell in
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guard let `self` = self else { return }
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self.reloadCellAtIndex((cell, index, self.pageIndex))
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cell.setNeedsLayout()
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}
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if let cell = visibleCells[pageIndex] {
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cellWillAppear(cell, pageIndex)
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}
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}
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}
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