CollectionView
// UICollectionView :集合视图.可布局出来各种展示效果,可支持多列展示数据,支持两个方向滚动(或)
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
//每个item的大小
layout.itemSize = CGSizeMake(100, 100);
//2.设置分区的缩进量 上, 左, 下,右,
layout.sectionInset = UIEdgeInsetsMake(5, 10, 5, 5);
//3.设置最小item间距
layout.minimumInteritemSpacing = 10;
//4.设置最小的行间距
layout.minimumLineSpacing = 20;
//5.设置滑动方向
// layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;//水平方向
//6.设置页眉的高度
layout.headerReferenceSize = CGSizeMake(100, 200);
layout.footerReferenceSize = CGSizeMake(100, 200);
//创建
UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:[UIScreen mainScreen].boundscollectionViewLayout:layout];
//配置属性
collectionView.dataSource = self;
//注册cell
[collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"item"];
//注册页眉
[collectionView registerClass:[HeaderView class]forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
//注册页脚
[collectionView registerClass:[UICollectionReusableView class]forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"footer"];
//代理
collectionView.delegate = self;
//加载到根视图
[self.view addSubview:collectionView];