//
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// LMJElementsFlowLayout.m
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//
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// Created by apple on 17/4/19.
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// Copyright © 2017年 NJHu. All rights reserved.
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//
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#import "LMJElementsFlowLayout.h"
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#define LMJXX(x) floorf(x)
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#define LMJXS(s) ceilf(s)
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static const CGFloat LMJ_XMargin_ = 10;
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static const CGFloat LMJ_YMargin_ = 10;
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static const UIEdgeInsets LMJ_EdgeInsets_ = {20, 10, 10, 10};
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@interface LMJElementsFlowLayout()
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/** 所有的cell的attrbts */
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@property (nonatomic, strong) NSMutableArray<UICollectionViewLayoutAttributes *> *lmj_AtrbsArray;
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/** 每一列的最后的高度 */
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@property (assign, nonatomic) CGRect lmj_LastAtrbsFrame;
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- (CGFloat)xMarginAtIndexPath:(NSIndexPath *)indexPath;
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- (CGFloat)yMarginAtIndexPath:(NSIndexPath *)indexPath;
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- (UIEdgeInsets)edgeInsets;
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- (CGRect)maxHeightFrame;
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@end
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@implementation LMJElementsFlowLayout
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/**
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* 刷新布局的时候回重新调用
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*/
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- (void)prepareLayout
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{
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[super prepareLayout];
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//如果重新刷新就需要移除之前存储的高度
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//复赋值以顶部的高度, 并且根据列数
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self.lmj_LastAtrbsFrame = CGRectMake(0, 0, self.collectionView.frame.size.width, 0);
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// 移除以前计算的cells的attrbs
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[self.lmj_AtrbsArray removeAllObjects];
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// 并且重新计算, 每个cell对应的atrbs, 保存到数组
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for (NSInteger i = 0; i < [self.collectionView numberOfItemsInSection:0]; i++)
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{
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[self.lmj_AtrbsArray addObject:[self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:0]]];
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}
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}
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/**
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*在这里边所处每个cell对应的位置和大小
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*/
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- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
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{
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UICollectionViewLayoutAttributes *atrbs = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
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// 原来的
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CGSize itemSize = [self.delegate waterflowLayout:self collectionView:self.collectionView sizeForItemAtIndexPath:indexPath];
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CGFloat w = LMJXX(itemSize.width);
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w = MIN(w, self.collectionView.frame.size.width);
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// 高度由外界决定, 外界必须实现这个方法
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CGFloat h = itemSize.height;
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// 拿到最后的高度最小的那一列, 假设第0列最小
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CGFloat rightLeftWidth = self.collectionView.frame.size.width - CGRectGetMaxX(self.lmj_LastAtrbsFrame) - [self xMarginAtIndexPath:indexPath] - self.edgeInsets.right;
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CGFloat x = self.edgeInsets.left;
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CGFloat y = self.edgeInsets.top;
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if (rightLeftWidth >= w) {
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x = CGRectGetMaxX(self.lmj_LastAtrbsFrame) + [self xMarginAtIndexPath:indexPath];
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y = self.lmj_LastAtrbsFrame.origin.y;
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}else
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{
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x = self.edgeInsets.left;
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y = CGRectGetMaxY(self.maxHeightFrame) + [self yMarginAtIndexPath:indexPath];
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}
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if (w > self.collectionView.frame.size.width - self.edgeInsets.left - self.edgeInsets.right) {
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x = (self.collectionView.frame.size.width - w) * 0.5;
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}
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if (y <= [self yMarginAtIndexPath:indexPath]) {
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y = self.edgeInsets.top;
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}
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// 赋值frame
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atrbs.frame = CGRectMake(x, y, w, h);
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// 覆盖添加完后那一列;的最新高度
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self.lmj_LastAtrbsFrame = atrbs.frame;
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return atrbs;
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}
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- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
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{
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return self.lmj_AtrbsArray;
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}
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- (CGRect)maxHeightFrame
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{
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__block CGRect maxHeightFrame = self.lmj_LastAtrbsFrame;
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[self.lmj_AtrbsArray enumerateObjectsUsingBlock:^(UICollectionViewLayoutAttributes * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
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if (CGRectGetMaxY(obj.frame) > CGRectGetMaxY(maxHeightFrame)) {
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maxHeightFrame = obj.frame;
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}
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}];
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return maxHeightFrame;
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}
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- (CGSize)collectionViewContentSize
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{
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return CGSizeMake(self.collectionView.frame.size.width, CGRectGetMaxY(self.maxHeightFrame) + self.edgeInsets.bottom);
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}
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- (NSMutableArray *)lmj_AtrbsArray
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{
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if(_lmj_AtrbsArray == nil)
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{
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_lmj_AtrbsArray = [NSMutableArray array];
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}
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return _lmj_AtrbsArray;
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}
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- (CGFloat)xMarginAtIndexPath:(NSIndexPath *)indexPath
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{
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if([self.delegate respondsToSelector:@selector(waterflowLayout:collectionView:columnsMarginForItemAtIndexPath:)])
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{
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return [self.delegate waterflowLayout:self collectionView:self.collectionView columnsMarginForItemAtIndexPath:indexPath];
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}
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else
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{
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return LMJ_XMargin_;
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}
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}
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- (CGFloat)yMarginAtIndexPath:(NSIndexPath *)indexPath
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{
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if([self.delegate respondsToSelector:@selector(waterflowLayout:collectionView:linesMarginForItemAtIndexPath:)])
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{
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return [self.delegate waterflowLayout:self collectionView:self.collectionView linesMarginForItemAtIndexPath:indexPath];
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}else
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{
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return LMJ_YMargin_;
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}
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}
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- (UIEdgeInsets)edgeInsets
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{
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if([self.delegate respondsToSelector:@selector(waterflowLayout:edgeInsetsInCollectionView:)])
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{
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return [self.delegate waterflowLayout:self edgeInsetsInCollectionView:self.collectionView];
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}
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else
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{
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return LMJ_EdgeInsets_;
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}
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}
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- (id<LMJElementsFlowLayoutDelegate>)delegate
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{
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return (id<LMJElementsFlowLayoutDelegate>)self.collectionView.dataSource;
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}
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- (instancetype)initWithDelegate:(id<LMJElementsFlowLayoutDelegate>)delegate
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{
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if (self = [super init]) {
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}
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return self;
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}
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+ (instancetype)flowLayoutWithDelegate:(id<LMJElementsFlowLayoutDelegate>)delegate
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{
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return [[self alloc] initWithDelegate:delegate];
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}
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@end
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