关于UICollectionView横向分页滚动,cell左右排

实现了对UICollectionView横向滑动的时候UICollectionViewCell横向排列的功能，并带有分组功能
先看下效果图

未命名.gif

废话不多说直接上代码

#import <UIKit/UIKit.h>

@interface ELCVFlowLayout : UICollectionViewFlowLayout

@end

#import "ELCVFlowLayout.h"

@interface ELCVFlowLayout ()

@property (nonatomic, copy) NSMutableDictionary *sectionDic;
@property (strong, nonatomic) NSMutableArray *allAttributes;

@end

@implementation ELCVFlowLayout


- (instancetype)init
{
   self = [super init];
   if (self) {
       self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
   }
   return self;
}


- (void)prepareLayout
{
   [super prepareLayout];

   _sectionDic = [NSMutableDictionary dictionary];
   self.allAttributes = [NSMutableArray array];
   //获取section的数量
   NSUInteger section = [self.collectionView numberOfSections];
   
   for (int sec = 0; sec < section; sec++) {
       //获取每个section的cell个数
       NSUInteger count = [self.collectionView numberOfItemsInSection:sec];
       
       for (NSUInteger item = 0; item<count; item++) {
           NSIndexPath *indexPath = [NSIndexPath indexPathForItem:item inSection:sec];
           //重新排列
           UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:indexPath];
           [self.allAttributes addObject:attributes];

       }
   }

}

- (CGSize)collectionViewContentSize
{

   //每个section的页码的总数
   NSInteger actualLo = 0;
   for (NSString *key in [_sectionDic allKeys]) {
       actualLo += [_sectionDic[key] integerValue];
   }
   
   
   return CGSizeMake(actualLo*self.collectionView.frame.size.width, self.collectionView.contentSize.height);
}

- (void)applyLayoutAttributes:(UICollectionViewLayoutAttributes *)attributes
{
   
   if(attributes.representedElementKind != nil)
   {
       return;
   }
   
   /*修改by lixinkai 2017.6.30
   下面这两个方法 itemW、itemH
    解决了同一个UICollectionView使用不同UICollectionViewCell的问题
    */
   //attributes 的宽度
   CGFloat itemW = attributes.frame.size.width;
   //attributes 的高度
   CGFloat itemH = attributes.frame.size.height;
   
   //collectionView 的宽度
   CGFloat width = self.collectionView.frame.size.width;
   //collectionView 的高度
   CGFloat height = self.collectionView.frame.size.height;
   //每个attributes的下标值 从0开始
   NSInteger itemIndex = attributes.indexPath.item;
   
   CGFloat stride = (self.scrollDirection == UICollectionViewScrollDirectionHorizontal) ? width : height;
   
   
   //获取现在的attributes是第几组
   NSInteger section = attributes.indexPath.section;
   //获取每个section的item的个数
   NSInteger itemCount = [self.collectionView numberOfItemsInSection:section];

   
   CGFloat offset = section * stride;
   
   //计算x方向item个数
   NSInteger xCount = (width / itemW);
   //计算y方向item个数
   NSInteger yCount = (height / itemH);
   //计算一页总个数
   NSInteger allCount = (xCount * yCount);
   //获取每个section的页数，从0开始
   NSInteger page = itemIndex / allCount;
   
   //余数，用来计算item的x的偏移量
   NSInteger remain = (itemIndex % xCount);
   
   //取商，用来计算item的y的偏移量
   NSInteger merchant = (itemIndex-page*allCount)/xCount;


   //x方向每个item的偏移量
   CGFloat xCellOffset = remain * itemW;
   //y方向每个item的偏移量
   CGFloat yCellOffset = merchant * itemH;
   
   //获取每个section中item占了几页
   NSInteger pageRe = (itemCount % allCount == 0)? (itemCount / allCount) : (itemCount / allCount) + 1;
   //将每个section与pageRe对应，计算下面的位置
   [_sectionDic setValue:@(pageRe) forKey:[NSString stringWithFormat:@"%ld", section]];
   
   if(self.scrollDirection == UICollectionViewScrollDirectionHorizontal) {
       
       NSInteger actualLo = 0;
       //将每个section中的页数相加
       for (NSString *key in [_sectionDic allKeys]) {
           actualLo += [_sectionDic[key] integerValue];
       }
       //获取到的最后的数减去最后一组的页码数
       actualLo -= [_sectionDic[[NSString stringWithFormat:@"%ld", [_sectionDic allKeys].count-1]] integerValue];
       xCellOffset += page*width + actualLo*width;

   } else {
       
       yCellOffset += offset;
   }
  
   attributes.frame = CGRectMake(xCellOffset, yCellOffset, itemW, itemH);
}

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
   
//    UICollectionViewLayoutAttributes *attr = [UICollectionViewLayoutAttributes  layoutAttributesForCellWithIndexPath:indexPath];
  UICollectionViewLayoutAttributes *attr = [super layoutAttributesForItemAtIndexPath:indexPath].copy;
   
   [self applyLayoutAttributes:attr];
   return attr;
}

- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
{
   return self.allAttributes;
}


@end

也可以直接下载
https://github.com/elite-kai/ELCVFlowLayout