实现协议 .h中

@interface HomeViewController : UIViewController <UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout>
@end

具体实现 .m

@interface HomeViewController ()
@end

UICollectionView *collectionView;

NSString *identifier = @"cellectionCell";

@implementation HomeViewController

- (void)viewDidLoad {
    [super viewDidLoad];
collectionView = [[UICollectionView alloc] initWithFrame:[[UIScreen mainScreen] bounds] collectionViewLayout:[[UICollectionViewFlowLayout alloc]init]];//初始化要设置一个flowlayout
collectionView.delegate = self;//设置代理
collectionView.dataSource = self;//设置数据源
collectionView.backgroundColor = [UIColor grayColor];
[collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:identifier];// 注册缓存标准
[self.view addSubview:collectionView];
}

//单元格数量

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return items.count;
 }

//选中事件

 - (void)collectionView:(UICollectionView *)collectionView     didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
UIBarButtonItem *backItem = [[UIBarButtonItem alloc] init];
backItem.title = @"返回";
self.navigationItem.backBarButtonItem = backItem;
[self.navigationController pushViewController:[[items objectAtIndex:indexPath.row] objectForKey:@"vc"] animated:YES];
}

//具体单元格

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = (UICollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
cell.backgroundColor = [UIColor whiteColor];
UIImageView *image = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, cell.frame.size.width, cell.frame.size.height - 30)];
image.contentMode = UIViewContentModeScaleAspectFill;
[image setImage:[UIImage imageNamed:@"ic_launcher"]];
CGFloat imageY = CGRectGetMaxY(image.frame);
UILabel *title = [[UILabel alloc] initWithFrame:CGRectMake(0, imageY, cell.frame.size.width, 30)];
title.text = [[items objectAtIndex:indexPath.row] objectForKey:@"title"];
[cell addSubview:image];
[cell addSubview:title];
return cell;
}

//分组数量

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}

//每个cell的大小
- (CGSize)collectionView:(UICollectionView )collectionView layout:(UICollectionViewLayout)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
float width = [[UIScreen mainScreen] bounds].size.width / 3 - 15;
return CGSizeMake(width, width + 30);
}

//距边界缩放大小

-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
return UIEdgeInsetsMake(10, 10, 10, 10);//分别为上、左、下、右
}