mirror of
https://github.com/568071718/creator-collection-view
synced 2025-04-22 00:58:42 +00:00
355 lines
14 KiB
Markdown
355 lines
14 KiB
Markdown
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通过二分查找优化 table-layout 性能
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```ts
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enum _yx_table_layout_supplementary_kinds {
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HEADER = 'header',
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FOOTER = 'footer',
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}
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export class YXTableLayout extends YXLayout {
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/**
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* 行高
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*/
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rowHeight: number | ((indexPath: YXIndexPath) => number) = 100
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/**
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* 内容上边距
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*/
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top: number = 0
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/**
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* 内容下边距
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*/
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bottom: number = 0
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/**
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* 节点之间间距
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*/
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spacing: number = 0
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/**
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* 区头高度
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*/
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sectionHeaderHeight: number | ((section: number) => number) = null
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/**
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* 区尾高度
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*/
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sectionFooterHeight: number | ((section: number) => number) = null
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/**
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* 钉住 header 的位置 ( header 吸附在列表可见范围内 )
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*/
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sectionHeadersPinToVisibleBounds: boolean = false
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/**
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* 钉住 footer 的位置 ( footer 吸附在列表可见范围内 )
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*/
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sectionFootersPinToVisibleBounds: boolean = false
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/**
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* 区头/区尾标识
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*/
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static SupplementaryKinds = _yx_table_layout_supplementary_kinds
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protected originalHeaderRect: Map<number, math.Rect> = new Map() // 保存所有 header 的原始位置
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protected originalFooterRect: Map<number, math.Rect> = new Map() // 保存所有 footer 的原始位置
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// 为了优化查找，额外维护几个数组按类别管理所有的布局属性，空间换时间
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protected allCellAttributes: YXLayoutAttributes[] = []
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protected allHeaderAttributes: YXLayoutAttributes[] = []
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protected allFooterAttributes: YXLayoutAttributes[] = []
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prepare(collectionView: YXCollectionView): void {
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// 设置列表的滚动方向(这套布局固定为垂直方向滚动)
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collectionView.scrollView.horizontal = false
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collectionView.scrollView.vertical = true
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if (collectionView.scrollDirection === YXCollectionView.ScrollDirection.HORIZONTAL) {
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// 由于这套布局规则只支持垂直方向布局，当外部配置了水平方向滚动时这里可以给个警告
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warn(`YXTableLayout 仅支持垂直方向排列`)
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}
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// 清空一下布局属性数组
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this.attributes = []
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this.allCellAttributes = []
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this.allHeaderAttributes = []
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this.allFooterAttributes = []
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this.originalHeaderRect.clear()
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this.originalFooterRect.clear()
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// 获取列表宽度
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const contentWidth = collectionView.node.getComponent(UITransform).width
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// 声明一个临时变量，用来记录当前所有内容的总高度
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let contentHeight = 0
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// 获取列表一共分多少个区
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let numberOfSections = collectionView.getNumberOfSections()
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// 为每条数据对应的生成一个布局属性
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for (let section = 0; section < numberOfSections; section++) {
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// 创建一个区索引
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let sectionIndexPath = new YXIndexPath(section, 0)
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// 通过区索引创建一个区头节点布局属性
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let sectionHeaderHeight = 0
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if (this.sectionHeaderHeight) {
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sectionHeaderHeight = this.sectionHeaderHeight instanceof Function ? this.sectionHeaderHeight(section) : this.sectionHeaderHeight
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}
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if (sectionHeaderHeight > 0) {
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let headerAttr = YXLayoutAttributes.layoutAttributesForSupplementary(sectionIndexPath, YXTableLayout.SupplementaryKinds.HEADER)
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// 确定这个节点的位置
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headerAttr.frame.x = 0
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headerAttr.frame.width = contentWidth
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headerAttr.frame.height = sectionHeaderHeight
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headerAttr.frame.y = contentHeight
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// 调整层级
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headerAttr.zIndex = 1
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// 重要: 保存布局属性
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this.attributes.push(headerAttr)
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this.originalHeaderRect.set(section, headerAttr.frame.clone())
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this.allHeaderAttributes.push(headerAttr)
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// 更新整体内容高度
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contentHeight = headerAttr.frame.yMax
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}
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// 将 top 配置应用到每个区
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contentHeight = contentHeight + this.top
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// 获取这个区内的内容数量，注意这里传入的是 section
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let numberOfItems = collectionView.getNumberOfItems(section)
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for (let item = 0; item < numberOfItems; item++) {
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// 创建索引，注意这里的 section 已经改为正确的 section 了
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let indexPath = new YXIndexPath(section, item)
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// 通过索引创建一个 cell 节点的布局属性
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let attr = YXLayoutAttributes.layoutAttributesForCell(indexPath)
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// 通过索引获取这个节点的高度
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let rowHeight = this.rowHeight instanceof Function ? this.rowHeight(indexPath) : this.rowHeight
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// 确定这个节点的位置
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attr.frame.x = 0
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attr.frame.width = contentWidth
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attr.frame.height = rowHeight
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attr.frame.y = contentHeight + (item > 0 ? this.spacing : 0)
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// 重要: 保存布局属性
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this.attributes.push(attr)
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this.allCellAttributes.push(attr)
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// 更新当前内容高度
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contentHeight = attr.frame.yMax
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}
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// 高度补一个底部间距，跟 top 一样，也是应用到每个区
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contentHeight = contentHeight + this.bottom
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// 通过区索引创建一个区尾节点布局属性
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let sectionFooterHeight = 0
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if (this.sectionFooterHeight) {
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sectionFooterHeight = this.sectionFooterHeight instanceof Function ? this.sectionFooterHeight(section) : this.sectionFooterHeight
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}
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if (sectionFooterHeight > 0) {
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let footerAttr = YXLayoutAttributes.layoutAttributesForSupplementary(sectionIndexPath, YXTableLayout.SupplementaryKinds.FOOTER)
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// 确定这个节点的位置
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footerAttr.frame.x = 0
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footerAttr.frame.width = contentWidth
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footerAttr.frame.height = sectionFooterHeight
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footerAttr.frame.y = contentHeight
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// 调整层级
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footerAttr.zIndex = 1
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// 重要: 保存布局属性
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this.attributes.push(footerAttr)
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this.originalFooterRect.set(section, footerAttr.frame.clone())
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this.allFooterAttributes.push(footerAttr)
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// 更新整体内容高度
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contentHeight = footerAttr.frame.yMax
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}
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}
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// 重要: 设置内容区域总大小，只有确定了滚动区域的大小列表才能滚动
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this.contentSize = new math.Size(contentWidth, contentHeight)
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}
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initOffset(collectionView: YXCollectionView): void {
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// 列表首次刷新时，调整一下列表的偏移位置
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collectionView.scrollView.scrollToTop()
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}
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layoutAttributesForElementsInRect(rect: math.Rect, collectionView: YXCollectionView): YXLayoutAttributes[] {
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let result = this.visibleElementsInRect(rect, collectionView)
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if (this.sectionHeadersPinToVisibleBounds == false && this.sectionFootersPinToVisibleBounds == false) {
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return result // 不需要调整节点位置，直接返回就好
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}
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let numberOfSections = collectionView.getNumberOfSections()
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let scrollOffset = collectionView.scrollView.getScrollOffset()
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for (let index = 0; index < result.length; index++) {
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const element = result[index];
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if (element.elementCategory === 'Supplementary') {
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if (this.sectionHeadersPinToVisibleBounds && element.supplementaryKinds === YXTableLayout.SupplementaryKinds.HEADER) {
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const originalFrame = this.originalHeaderRect.get(element.indexPath.section)
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element.frame.y = originalFrame.y
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if (scrollOffset.y > originalFrame.y) {
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element.frame.y = scrollOffset.y
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}
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const nextOriginalFrame = this.getNextOriginalFrame(element.indexPath.section, YXTableLayout.SupplementaryKinds.FOOTER, numberOfSections)
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if (nextOriginalFrame) {
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if (element.frame.yMax > nextOriginalFrame.y) {
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element.frame.y = nextOriginalFrame.y - element.frame.height
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}
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}
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}
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if (this.sectionFootersPinToVisibleBounds && element.supplementaryKinds === YXTableLayout.SupplementaryKinds.FOOTER) {
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let bottom = scrollOffset.y + collectionView.scrollView.view.height
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const originalFrame = this.originalFooterRect.get(element.indexPath.section)
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const previousOriginalFrame = this.getPreviousOriginalFrame(element.indexPath.section, YXTableLayout.SupplementaryKinds.HEADER)
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element.frame.y = originalFrame.y
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if (bottom < originalFrame.yMax) {
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element.frame.y = bottom - element.frame.height
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if (previousOriginalFrame) {
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if (element.frame.y < previousOriginalFrame.yMax) {
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element.frame.y = previousOriginalFrame.yMax
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}
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}
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}
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}
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}
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}
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return result
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}
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shouldUpdateAttributesZIndex(): boolean {
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return this.sectionHeadersPinToVisibleBounds || this.sectionFootersPinToVisibleBounds
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}
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shouldUpdateAttributesForBoundsChange(): boolean {
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return this.sectionHeadersPinToVisibleBounds || this.sectionFootersPinToVisibleBounds
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}
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/**
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* 获取 `section` 下一个 header 或者 footer 的位置
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*/
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protected getNextOriginalFrame(section: number, kinds: _yx_table_layout_supplementary_kinds, total: number) {
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if (section >= total) { return null }
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if (kinds === YXTableLayout.SupplementaryKinds.HEADER) {
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let result = this.originalHeaderRect.get(section)
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if (result) { return result }
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return this.getNextOriginalFrame(section, YXTableLayout.SupplementaryKinds.FOOTER, total)
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}
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if (kinds === YXTableLayout.SupplementaryKinds.FOOTER) {
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let result = this.originalFooterRect.get(section)
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if (result) { return result }
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return this.getNextOriginalFrame(section + 1, YXTableLayout.SupplementaryKinds.HEADER, total)
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}
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return null
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}
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/**
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* 获取 `section` 前一个 header 或者 footer 的位置
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*/
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protected getPreviousOriginalFrame(section: number, kinds: _yx_table_layout_supplementary_kinds) {
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if (section < 0) { return null }
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if (kinds === YXTableLayout.SupplementaryKinds.HEADER) {
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let result = this.originalHeaderRect.get(section)
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if (result) { return result }
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return this.getPreviousOriginalFrame(section - 1, YXTableLayout.SupplementaryKinds.FOOTER)
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}
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if (kinds === YXTableLayout.SupplementaryKinds.FOOTER) {
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let result = this.originalFooterRect.get(section)
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if (result) { return result }
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return this.getPreviousOriginalFrame(section, YXTableLayout.SupplementaryKinds.HEADER)
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}
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return null
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}
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/**
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* 抽出来一个方法用来优化列表性能
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* 在优化之前，可以先看一下 @see YXLayout.layoutAttributesForElementsInRect 关于返回值的说明
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* 对于有序列表来说，一般都是可以通过二分查找来进行优化
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*/
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protected visibleElementsInRect(rect: math.Rect, collectionView: YXCollectionView) {
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if (this.attributes.length <= 100) { return this.attributes } // 少量数据就不查了，直接返回全部
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let result: YXLayoutAttributes[] = []
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// header 跟 footer 暂时不考虑，数据相对来说不算很多，直接全部返回
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result.push(...this.allHeaderAttributes)
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result.push(...this.allFooterAttributes)
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// 关于 cell，这里用二分查找来优化一下
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// 首先通过二分先查出个大概位置
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let midIdx = -1
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let left = 0
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let right = this.allCellAttributes.length - 1
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while (left <= right && right >= 0) {
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let mid = left + (right - left) / 2
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mid = Math.floor(mid)
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let attr = this.allCellAttributes[mid]
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if (rect.intersects(attr.frame)) {
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midIdx = mid
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break
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}
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if (rect.yMax < attr.frame.yMin || rect.xMax < attr.frame.xMin) {
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right = mid - 1
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} else {
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left = mid + 1
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}
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}
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// 二分查找出错了，返回全部的布局属性
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if (midIdx < 0) {
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return this.attributes
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}
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// 把模糊查到这个先加进来
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result.push(this.allCellAttributes[midIdx])
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// 然后依次往前检查，直到超出当前的显示范围
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let startIdx = midIdx
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while (startIdx > 0) {
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let idx = startIdx - 1
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let attr = this.allCellAttributes[idx]
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if (rect.intersects(attr.frame) == false) {
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break
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}
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result.push(attr)
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startIdx = idx
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}
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// 依次往后检查，直到超出当前的显示范围
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let endIdx = midIdx
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while (endIdx < this.allCellAttributes.length - 1) {
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let idx = endIdx + 1
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let attr = this.allCellAttributes[idx]
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if (rect.intersects(attr.frame) == false) {
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break
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}
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result.push(attr)
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endIdx = idx
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}
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return result
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}
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}
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```
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