//自定义布局，继承于UICollectionViewLayout
#import <UIKit/UIKit.h>
@class WaterFlowLayout;
@protocol WaterFlowLayoutDeleagre ;
@interface WaterFlowLayout : UICollectionViewLayout
@property (nonatomic,weak)id<WaterFlowLayoutDeleagre>delegate;
@end
@protocol WaterFlowLayoutDeleagre <NSObject>
@required
- (CGFloat)collectionView:(__kindof UICollectionView *)collectionView heightForItemAtIndexPath:(NSIndexPath *)indexPath;
@end
-------------------------------------------------------------------------
#import "WaterFlowLayout.h"
static CGFloat const coloumMarginDefault = 10; //间隙
static NSInteger const coloumDefault = 3; //这里可以更改列数
static CGFloat const rowMaginDegault = 10; //行之间的间隙
@interface WaterFlowLayout ()
@property (nonatomic,strong)NSMutableArray * attris;
@property (nonatomic,strong)NSMutableArray * cloumsHeight;
@end
@implementation WaterFlowLayout
//记录没列cell的最大Y值
- (NSMutableArray *)cloumsHeight
{
if (_cloumsHeight == nil) {
_cloumsHeight = [NSMutableArray array];
}
return _cloumsHeight;
}
//存放每个cell的属性值
- (NSMutableArray *)attris
{
if (_attris == nil) {
_attris = [NSMutableArray array];
}
return _attris;
}
//准备开始布局
- (void)prepareLayout
{
[super prepareLayout];
//布局开始之前清空所有的列高度
[self.cloumsHeight removeAllObjects];
//为列高度添加初始值
for (int i=0; i<coloumDefault; i++) {
[self.cloumsHeight addObject:@0];
}
//获取对应组的cell个数
NSInteger count = [self.collectionView numberOfItemsInSection:0];
NSMutableArray * atts = [NSMutableArray array];
//创建cell的布局属性
for (int i=0; i<count; i++) {
//获取collectionview中对应indexpath的cell属性
UICollectionViewLayoutAttributes * attributes = [self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:0]];
[atts addObject:attributes];
}
self.attris = atts;
}
- (nullable NSArray<__kindof UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{
//返回所有cell的布局属性
return self.attris;
}
- (UICollectionViewLayoutAttributes*)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
//初始化布局属性
UICollectionViewLayoutAttributes * attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
//让纪律每列高度中的数组的第一个数据为最小值
CGFloat minHeight = [self.cloumsHeight[0] floatValue];
//记录的列号
NSInteger cloum =0;
//取出最小高度的列
for ( NSInteger i=1; i<self.cloumsHeight.count; i++) {
if (minHeight > [self.cloumsHeight[i] floatValue]) {
minHeight = [self.cloumsHeight[i] floatValue];
cloum =i;
}
}
//计算宽度
CGFloat W = (self.collectionView.frame.size.width - coloumMarginDefault * (coloumDefault + 1))/ coloumDefault;
//计算高度
CGFloat H = [self.delegate collectionView:self.collectionView heightForItemAtIndexPath:indexPath];
//计算cell的x值
CGFloat X = coloumMarginDefault + (W + coloumMarginDefault) *cloum;
//计算cell的Y值
CGFloat Y = minHeight + rowMaginDegault;
attributes.frame = CGRectMake(X, Y, W, H);
//更新记录每列高度的数组
[self.cloumsHeight replaceObjectAtIndex:cloum withObject:@(CGRectGetMaxY(attributes.frame) )];
return attributes;
}
//返回collectionview的滚动范围
- (CGSize)collectionViewContentSize
{
CGFloat maxHeight = 0;
for (int i=0; i<self.cloumsHeight.count; i++) {
if (maxHeight < [self.cloumsHeight[i] floatValue]) {
maxHeight =[self.cloumsHeight[i] floatValue];
}
}
return CGSizeMake(0, maxHeight);
}
@end
-----------------------------------------------------------------------------------------------如此即可------------------------------------------------
