import "ViewController.h"

@interface ViewController ()<UICollectionViewDelegate,UICollectionViewDataSource>
{
UICollectionView *collection; //网格视图
}

@end

//设置可重用标识符
static NSString * const reuseID = @"cell";

@implementation ViewController

• (void)viewDidLoad {
  [super viewDidLoad];

  //创建一个布局对象
  UICollectionViewFlowLayout *flowlayout = [[UICollectionViewFlowLayout alloc]init];

  //设置每个格子的大小
  flowlayout.itemSize = CGSizeMake(100, 100);

  //设置每个格子的最小水平间距
  flowlayout.minimumInteritemSpacing = 20;

  //设置行间距 最小行间距
  flowlayout.minimumLineSpacing = 20;

  //设置组与组之间的间隔
  flowlayout.sectionInset = UIEdgeInsetsMake(50, 10, 0, 10);
  //创建网格对象
  collection = [[UICollectionView alloc]initWithFrame:self.view.frame collectionViewLayout:flowlayout];

  //设置代理
  collection.delegate = self;
  collection.dataSource = self;

  //设置网格背景颜色
  collection.backgroundColor = [UIColor greenColor];

  //注册cell
  [collection registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:reuseID];

  //将网格添加到父视图上
  [self.view addSubview:collection];
  }

//=========数据源方法=========

//设置组数

• (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
  {
  return 5;
  }

//设置行数

• (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
  {
  return 5;
  }

//设置 cell 内容

• (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
  {

//根据可重用标识符查找cell
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseID forIndexPath:indexPath];

//设置cell的背景颜色
cell.backgroundColor = [UIColor colorWithRed:((float)arc4random_uniform(256) / 255.0)green:((float)arc4random_uniform(256) / 255.0)blue:((float)arc4random_uniform(256) / 255.0)alpha:1.0];

return cell;

}