import "ViewController.h"

@interface ViewController ()<UICollectionViewDelegate,UICollectionViewDataSource>
{
UICollectionView *collection; //網格視圖
}

@end

//設置可重用標識符
static NSString * const reuseID = @"cell";

@implementation ViewController

• (void)viewDidLoad {
  [super viewDidLoad];

  //創建一個布局對象
  UICollectionViewFlowLayout *flowlayout = [[UICollectionViewFlowLayout alloc]init];

  //設置每個格子的大小
  flowlayout.itemSize = CGSizeMake(100, 100);

  //設置每個格子的最小水平間距
  flowlayout.minimumInteritemSpacing = 20;

  //設置行間距 最小行間距
  flowlayout.minimumLineSpacing = 20;

  //設置組與組之間的間隔
  flowlayout.sectionInset = UIEdgeInsetsMake(50, 10, 0, 10);
  //創建網格對象
  collection = [[UICollectionView alloc]initWithFrame:self.view.frame collectionViewLayout:flowlayout];

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

  //設置網格背景顏色
  collection.backgroundColor = [UIColor greenColor];

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

  //將網格添加到父視圖上
  [self.view addSubview:collection];
  }

//=========數據源方法=========

//設置組數

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

//設置行數

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

//設置 cell 內容

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

//根據可重用標識符查找cell
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseID forIndexPath:indexPath];

//設置cell的背景顏色
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;

}