//
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// WaterFallFlowLayout.swift
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// WanPai
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//
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// Created by 杨锴 on 2023/6/8.
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//
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import UIKit
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protocol WaterFallLayoutDelegate: NSObjectProtocol {
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func waterFlowLayout(_ waterFlowLayout: WaterFallFlowLayout, itemHeight indexPath: IndexPath) -> CGFloat
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}
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@available(*,deprecated,message: "废弃")
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class WaterFallFlowLayout: UICollectionViewFlowLayout {
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weak var delegate: WaterFallLayoutDelegate?
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// 列数
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var cols = 4
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var itemCount:Int = 0
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// 布局数组
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var layoutAttributeArray: [UICollectionViewLayoutAttributes] = []
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// 高度数组
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fileprivate lazy var yArray: [CGFloat] = Array(repeating: self.sectionInset.top, count: cols)
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fileprivate var maxHeight: CGFloat = 0
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override func prepare() {
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super.prepare()
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// 计算每个 Cell 的宽度
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let itemWidth = (collectionView!.bounds.width - sectionInset.left - sectionInset.right - minimumInteritemSpacing * CGFloat(cols - 1)) / CGFloat(cols)
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// Cell 数量
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// let itemCount = collectionView!.numberOfItems(inSection: 0)
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// 最小高度索引
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var minHeightIndex = 0
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// 遍历 item 计算并缓存属性
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for i in layoutAttributeArray.count ..< itemCount {
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let indexPath = IndexPath(item: i, section: 0)
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let attr = UICollectionViewLayoutAttributes(forCellWith: indexPath)
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// 获取动态高度
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let itemHeight = delegate?.waterFlowLayout(self, itemHeight: indexPath)
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// 找到高度最短的那一列
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let value = yArray.min()
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// 获取数组索引
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minHeightIndex = yArray.firstIndex(of: value!)!
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// 获取该列的 Y 坐标
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var itemY = yArray[minHeightIndex]
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// 判断是否是第一行，如果换行需要加上行间距
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if i >= cols {
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itemY += minimumInteritemSpacing
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}
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// 计算该索引的 X 坐标
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let itemX = sectionInset.left + (itemWidth + minimumInteritemSpacing) * CGFloat(minHeightIndex)
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// 赋值新的位置信息
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attr.frame = CGRect(x: itemX, y: itemY, width: itemWidth, height: CGFloat(itemHeight!))
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// 缓存布局属性
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layoutAttributeArray.append(attr)
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// 更新最短高度列的数据
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yArray[minHeightIndex] = attr.frame.maxY
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}
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maxHeight = yArray.max()! + sectionInset.bottom
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}
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}
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extension WaterFallFlowLayout {
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override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
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// 返回相交的区域
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return layoutAttributeArray.filter {
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$0.frame.intersects(rect)
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}
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}
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override var collectionViewContentSize: CGSize {
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return CGSize(width: collectionView!.bounds.width, height: maxHeight)
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}
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}
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