关于UICollectionView在MRC下的纯代码实现之一（在UIViewController中实现）

#import "AppDelegate.h"
#import "ViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate
- (void)dealloc
{
    [_window release];
    [super dealloc];
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    ViewController *rootVC = [[ViewController alloc]init];
    //导航控制器
    UINavigationController *navi = [[UINavigationController alloc]initWithRootViewController:rootVC];
    //将导航控制器设置为主视图控制器根视图控制器
    self.window.rootViewController = navi;
    //释放所有权
    [navi release];
    [rootVC release];
    return YES;
}

#import "ViewController.h"

@interface ViewController ()<UICollectionViewDataSource,UICollectionViewDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.navigationController.title = @"集合视图";
    
    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
    int colums = 3;
    CGFloat viewWidth = self.view.frame.size.width;
    
    //配置属性
    //1.设置每个item的大小
    layout.itemSize = CGSizeMake((viewWidth - (colums - 1) * 60)/colums , 120);
    //2.设置缩进量（上下左右四个方向）
    layout.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);
    //3.设置每行的最小行间距
    layout.minimumLineSpacing = 30;
    //4.设置item之间的最小边距
    layout.minimumInteritemSpacing = 30;
    //5.设置滑动的方向,分为横向滑动和竖向滑动，默认是纵向滑动
    layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    //6.设置页眉(横向滑动情况下默认高为整个屏幕高，纵向滑动情况下默认宽是整个屏幕宽)
    layout.headerReferenceSize = CGSizeMake(30, 30);
    //7.设置页脚
    layout.footerReferenceSize = CGSizeMake(60, 60);
    //建立UICollectionView
    UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:self.view.bounds collectionViewLayout:layout];
    //默认背景色为黑色
    collectionView.backgroundColor = [UIColor whiteColor];
    //设置代理监听事件
    collectionView.delegate = self;
    //提供数据
    collectionView.dataSource = self;
    [self.view addSubview:collectionView];
    [collectionView release];
    [layout release];
    
    //注册cell
    [collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
    //注册页眉
    [collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
    //注册页脚
    [collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"footer"];
    
}

//section的个数
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
    return 3;
}


//一个section的item数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return 10;
}

//返回cell
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    cell.backgroundColor = [UIColor redColor];
    return cell;
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
    if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
        //返回页眉
        UICollectionReusableView *header = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"header" forIndexPath:indexPath];
        header.backgroundColor = [UIColor yellowColor];
        return header;
    } else {
        //返回页脚
        UICollectionReusableView *footer = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"footer" forIndexPath:indexPath];
        footer.backgroundColor = [UIColor orangeColor];
        return footer;
    }
}