CollectionView的基础代码

#import "ViewController.h"

#define CellIdentifier @"CellIdentifier"

#define Header @"Header"

#define Footer @"Footer"


@interface ViewController ()<UICollectionViewDelegate,UICollectionViewDataSource>

@property (nonatomic,strong) UICollectionView *collectionView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    //
    //创建 layout(此处创建的是流水布局)

    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    
    //行距
    
    flowLayout.minimumLineSpacing = 10;
    
    //列距
    
    flowLayout.minimumInteritemSpacing = 10;
    
    //设置每个 item 的大小
    
    flowLayout.itemSize = CGSizeMake(([UIScreen mainScreen].bounds.size.width -40)/3, ([UIScreen mainScreen].bounds.size.height-80)/4);
    
    //设置 item 的上左下右的边距大小
    
    flowLayout.sectionInset = UIEdgeInsetsMake(10, 10, 20, 10);
    
    //设置 UICollectionView 的滑动方向
    
    flowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;
    
    //如果有头部view，设置这个sise
    
    flowLayout.headerReferenceSize = CGSizeMake(0, 20);
    
    //如果有尾部view，设置这个sise
    
    flowLayout.footerReferenceSize = CGSizeMake(0, 50);
    
    self.collectionView = [[UICollectionView alloc]initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
    self.collectionView.delegate =self;
    self.collectionView.dataSource =self;
    [self.view addSubview:self.collectionView];
    
    //注册 item
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:CellIdentifier];
    
    //注册头部区域
    [self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:Header];
    
    //注册尾部区域
    [self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:Footer];
    
}

#pragma mark ------------------------------UICollectionViewDataSource--------------------------------
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return 20;
}

// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
    
    cell.contentView.backgroundColor = [UIColor redColor];
    return cell;
}

#pragma mark -----------------------------UICollectionViewDelegate---------------------------------
//该方法用于设置 collectionView 的 header 和 footer
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
    
    //设置头部或尾部 view
    if (kind == UICollectionElementKindSectionHeader) {
        
        UICollectionReusableView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:Header forIndexPath:indexPath];
        headerView.backgroundColor = [UIColor orangeColor];
        return headerView;
    }
    else{
        
        UICollectionReusableView *footerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:Footer forIndexPath:indexPath];
        footerView.backgroundColor = [UIColor yellowColor];
        return footerView;
    }
}

//点击 cell 时调用响应的方法
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    
    NSLog(@"didselected = %lu",indexPath.row);
}