设置布局对象

   UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
    layout.minimumLineSpacing = relativeY(32);
    layout.minimumInteritemSpacing = relativeY(26);
    //设置滚动方向
    //     layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    CGFloat itemHeight = relativeY(100);
    CGFloat itemWidth = relativeY(210);
    layout.itemSize = CGSizeMake(itemWidth, itemHeight);
    
    //设置头部尺寸
    layout.headerReferenceSize=CGSizeMake(SCREEN_WIDTH, relativeY(160));
    //设置底部尺寸
    layout.footerReferenceSize = CGSizeMake(SCREEN_WIDTH, relativeY(96 + 60));
    
    
    
    //创建collectionView
    UICollectionView * exchangeView = [[UICollectionView alloc] initWithFrame:CGRectMake(relativeY(32), relativeY(248), SCREEN_WIDTH - relativeY(64), relativeY(60 + 100 + 32 + 100 + 60)) collectionViewLayout:layout];
    self.exchangeView = exchangeView;
    [self.view addSubview:exchangeView];
    exchangeView.backgroundColor = [UIColor greenColor];
    exchangeView.delegate = self;
    exchangeView.dataSource = self;
    
    //注册相关的视图
    //可注册多个类型cell
    [exchangeView registerClass:[DWHWSBToDiamondCell class] forCellWithReuseIdentifier:WSBToDiamond];
    [exchangeView registerClass:[DWHWSBToRMBCell class] forCellWithReuseIdentifier:WSBToRMB];
    //注册头部视图和底部视图
    [exchangeView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerViewIdentifier];
    [exchangeView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:footerViewIdentifier];
    

❗️ collectionView的frame高度应该加上header和footer的高度

设置头部和底部的view

//  返回头视图 底视图
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    //如果是头视图
    if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
        UICollectionReusableView *header=[collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:headerViewIdentifier forIndexPath:indexPath];
          //❗️header就是头部 将自定义的头部视图内容加到header即可

        //添加头视图的内容
        [self addContent];
        //头视图添加view
        [header addSubview:self.headerView];
        return header;
    }
      //    如果底部视图
        if([kind isEqualToString:UICollectionElementKindSectionFooter]){
            UICollectionReusableView *footer=[collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:footerViewIdentifier forIndexPath:indexPath];
            
            //添加头视图的内容
            [self configureFooter];
            
            //头视图添加view
            [footer addSubview:self.footer];
            return footer;

        }
    return nil;
}

自定义CollectionViewCell

#import <UIKit/UIKit.h>
#import "DWHWSBToRMBModel.h"


@interface DWHWSBToRMBCell : UICollectionViewCell

@property (nonatomic,strong) DWHWSBToRMBModel * model;

@end

#import "DWHWSBToRMBCell.h"

@interface DWHWSBToRMBCell ()

@property (nonatomic ,strong ) UILabel * wsbLabel;

@property (nonatomic ,strong ) UILabel * rmbLabel;

@end


@implementation DWHWSBToRMBCell


- (instancetype)initWithFrame:(CGRect)frame{
    
    if (self = [super initWithFrame:frame]) {
        [self configureUI];
        
    }
    
    return self;
    
}



- (void)configureUI{

    self.contentView.layer.borderWidth = 1;
    self.contentView.layer.borderColor = DWHColorFromRGB(0xcccccc).CGColor;
    self.contentView.layer.cornerRadius = 10;
    self.contentView.layer.masksToBounds = YES;

     ......
     ......
}

• 设置默认选中某个cell选中,在返回cell方法里面设置即可
  - collectionView: cellForItemAtIndexPath:{
  if(........){
  cell.selected = YES;
  }
  }