#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"

#import "ImageViewCell.h"

#define SCREEN_WIDTH [UIScreen mainScreen].bounds.size.width

#define SCREEN_HEIGHT [UIScreen mainScreen].bounds.size.height

#define line_gap 10

#define interitem_gap 20

@interface RootViewController ()<UICollectionViewDataSource,UICollectionViewDelegate,UICollectionViewDelegateFlowLayout>

{

}

@end

static NSString *identifier = @"cell";

static NSString *headerIdentifier = @"header";

static NSString *flooterIdentifier = @"floot";

@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 = line_gap;

    //列的间隙

    layout.minimumInteritemSpacing = ;

    //item的大小

    layout.itemSize = CGSizeMake((SCREEN_WIDTH - *line_gap)/, );

    //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:[ImageViewCell class] forCellWithReuseIdentifier:identifier];

    // 注册头视图

    [collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerIdentifier];

    // 注册尾视图

    [collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:flooterIdentifier];

    [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{

    ImageViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];

    cell.photo.image = [UIImage imageNamed:@"cellPhoto"];

    return cell;

}

//返回头headerView的大小

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section{

    CGSize size = CGSizeMake(SCREEN_WIDTH, +line_gap);

    return size;

}

//返回头flooterView的大小

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section

{

    CGSize size = CGSizeMake(SCREEN_WIDTH, +line_gap);

    return size;

}

// 头和尾部显示的内容

- (UICollectionReusableView*)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{

    UICollectionReusableView *reusableView = nil;

    if (kind == UICollectionElementKindSectionHeader) {

        reusableView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerIdentifier forIndexPath:indexPath];

        UIImageView *headerPhoto = [[UIImageView alloc] initWithFrame:CGRectMake(, , SCREEN_WIDTH, )];

        headerPhoto.image = [UIImage imageNamed:@"headerPhoto"];

        [reusableView addSubview:headerPhoto];

    }else if (kind == UICollectionElementKindSectionFooter){

        reusableView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:flooterIdentifier forIndexPath:indexPath];

        UIImageView *flooterPhoto = [[UIImageView alloc] initWithFrame:CGRectMake(, line_gap, SCREEN_WIDTH, )];

        flooterPhoto.image = [UIImage imageNamed:@"flooterPhoto"];

        [reusableView addSubview:flooterPhoto];

    }

    return reusableView;

}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{

    NSLog(@"==%lu",indexPath.row);

}

@end

#import <UIKit/UIKit.h>

@interface ImageViewCell : UICollectionViewCell

@property (nonatomic, strong) UIImageView *photo;

@end

#import "ImageViewCell.h"

@implementation ImageViewCell

- (instancetype)initWithFrame:(CGRect)frame{

    if (self = [super initWithFrame:frame]) {

        self.photo = [[UIImageView alloc] init];

        self.photo.frame = self.bounds;

        [self addSubview:self.photo];

    }

    return self;

}

@end