- (instancetype)initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionViewLayout *)layout{

UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];

_flowLayout = flowLayout;

_flowLayout.minimumLineSpacing = 3;

_flowLayout.minimumInteritemSpacing = 3;

_flowLayout.headerReferenceSize = CGSizeMake(SCREEN_WIDTH, 35);

_flowLayout.footerReferenceSize = CGSizeMake(SCREEN_WIDTH, 10);

self = [super initWithFrame:CGRectZero collectionViewLayout:_flowLayout];

if (self) {

self.showsVerticalScrollIndicator = NO;

self.bounces = NO;

self.alwaysBounceVertical = NO;

self.scrollsToTop = YES;

// self.pagingEnabled = NO;

self.dataSource = self;

self.delegate = self;

//self.backgroundColor = [UIColor clearColor];

self.backgroundColor = OtherLineColor;

//注册cell单元格

[self registerClass:[CategoryCollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];

//下面的注册组的头尾部view，这个必须实现，否则会崩

//注册header单元格

[self registerClass:[CategoryCollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:ID];

//注册footer单元格

[self registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:footID];

}

return self;

}

//组的头尾部的代码实现

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{

UICollectionReusableView *reusableView = nil;

//组的头部

if (kind == UICollectionElementKindSectionHeader ) {

//CategoryCollectionReusableView是自定义的继承UICollectionReusableView的子类；

CategoryCollectionReusableView *categoryCollectionReusableView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:ID forIndexPath:indexPath];

if (indexPath.section == 0) {

categoryCollectionReusableView.title = @"全部分类";

}else if (indexPath.section == 1){

categoryCollectionReusableView.title = @"热门品牌";

}

reusableView = categoryCollectionReusableView;

}

//组的尾部

if (kind == UICollectionElementKindSectionFooter) {

UICollectionReusableView *footer = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:footID forIndexPath:indexPath];

reusableView = footer;

}

return reusableView;

}