iOS UICollectionView之二（垂直滚动）

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

#import "AppDelegate.h"
#import "RootViewController.h"
@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];

    self.window.rootViewController = [[RootViewController alloc] init];

    [self.window makeKeyAndVisible];
    return YES;
}

@end

#import <UIKit/UIKit.h>

@interface RootViewController : UIViewController

@end

#import "RootViewController.h"

@interface RootViewController ()<UICollectionViewDataSource,UICollectionViewDelegate>
{
}
@end
 static NSString *identifier = @"cell";
@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
   //创建布局对象
    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
    // 设置滚动的方向
    [layout setScrollDirection:UICollectionViewScrollDirectionVertical];
    //行的间隙
    layout.minimumLineSpacing = ;
    //列的间隙
//    layout.minimumInteritemSpacing = 10;
    //item的大小
    layout.itemSize = CGSizeMake([UIScreen mainScreen].bounds.size.width, );
    //创建collectionView
    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:[[UIScreen mainScreen] bounds] collectionViewLayout:layout];
    collectionView.backgroundColor = [UIColor greenColor];
    // 设置代理
    collectionView.dataSource = self;
    collectionView.delegate = self;
    //告诉系统将来需要创建什么样的cell(在获取cell之前必须先注册一个cell到系统中)
    [collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:identifier];
    [self.view addSubview:collectionView];
}
// 告诉系统一共有多少组
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
    return ;
}
// 告诉系统第section组有多少行
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return ;
}
// 告诉系统indexPath的第Section组的item行显示什么内容
- (UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
    cell.backgroundColor = [UIColor redColor];
    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    NSLog(@"==%lu",indexPath.row);
}

@end