iOS UICollectionView實用練習 —— HERO部落格

上一篇簡述了UICollectionView的屬性及方法，本篇實際應用練習使用。

具體屬性及方法可以參考上一篇UICollectionView簡介：UICollectionView簡介

執行個體1，首先看一下效果圖8-1：

下面貼上代碼，cell是自定義模型，不貼了，注重UICollectionView用法。

//建立布局
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
//滾動方向
[flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
//組間距
flowLayout.sectionInset = UIEdgeInsetsMake(10, 20, 10, 20);

@interface TestViewController ()
@property (nonatomic, strong) NSArray *array1;
@property (nonatomic, strong) NSArray *array2;
@property (nonatomic, strong) NSArray *array3;
@end

@implementation TestViewController
static NSString * const reuseIdentifier1 = @"Cell1";
static NSString * const reuseIdentifier2 = @"Cell2";
static NSString * const reuseIdentifier3 = @"Cell3";
static NSString * const Reusable = @"Reusable";

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //設定背景
    self.collectionView.backgroundColor = [UIColor whiteColor];
    //不回彈
    self.collectionView.bounces = NO;
    //隐藏垂直滾動條
    self.collectionView.showsVerticalScrollIndicator = NO;
    
    //注冊cell
    [self.collectionView registerClass:[TVACell class] forCellWithReuseIdentifier:reuseIdentifier1];
    [self.collectionView registerClass:[TVBCell class] forCellWithReuseIdentifier:reuseIdentifier2];
    [self.collectionView registerClass:[TVCCell class] forCellWithReuseIdentifier:reuseIdentifier3];
    //注冊ReusableView
    [self.collectionView registerClass:[TSView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:Reusable];
}

#pragma mark <UICollectionViewDataSource>
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return self.array3 + 2;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    if (section == 0) {
        return 1;
    } else if (section == 1) {
        return 3;
    }
    TVCModel *model = self.array3[section - 2];
    return model.array.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.section == 0) {
        
        TVACell *cell = [TVACell cellWithCollectionView:collectionView cellForItemAtIndexPath:indexPath];
        cell = [cell initWithArray:self.array1];
        return cell;
        
    } else if (indexPath.section == 1) {

        TVBCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier2 forIndexPath:indexPath];
        TVBModel *model = self.array2[indexPath.item];
        cell.model = model;
        return cell;
    }
    
    TVCCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier3 forIndexPath:indexPath];
    TVCModel *model = self.array3[indexPath.section - 2];
    cell.model = model.array[indexPath.item];
    return cell;
}

//cell尺寸
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.section == 0) {
        return CGSizeMake(mainW, mainH * 0.23);
        
    } else if (indexPath.section == 1) {
         return CGSizeMake(mainW * 0.25, mainW * 0.35);
    }
    
    CGFloat W = mainW * 0.25;
    return CGSizeMake(W, W);
}

//cell的最小行間距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 10.0f;
}

//margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    if (section == 0) {
        return UIEdgeInsetsMake(0, 0, 0, 0);
    }
    return UIEdgeInsetsMake(10, 20, 10, 20);
}

//cell的最小列間距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    return (mainW - mainW * 0.25 * 3) / 4;
}

//設定頂部的大小
-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
    if (section == 0) {
        CGSize size = {0, 0};
        return size;
    }
    
    CGSize size = {0, 40};
    return size;
}

//追加視圖
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.section == 1) {
        
        if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
            TSView *reusable = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:Reusable forIndexPath:indexPath];
            reusable.delegate = self;
            reusable.label.text = @"第二組追加視圖";
            reusable.button.hidden = NO;
            return reusable;
        }
    } else if(indexPath.section > 1) {
        
        TVCModel *model = self.array3[indexPath.section - 2];
        
        if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
            TSView *reusable = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:Reusable forIndexPath:indexPath];
            reusable.model = model;
            reusable.label.text = @"第三組追加視圖";
            reusable.button.hidden = YES;
            return reusable;
        }
    }
    return  nil;
}

//點選方法
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    if (indexPath.section == 1) {
        
    } else if (indexPath.section > 1) {

    }
}

@end
           

執行個體2，自定義了一個圓形布局，效果如圖8-2：

下面貼上代碼：

ViewController：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

#import "ViewController.h"
#import "HWCircleLayout.h"
#import "HWCollectionViewCell.h"

@interface ViewController ()<UICollectionViewDataSource>

@property (nonatomic, strong) UICollectionView *collectionView;
@property (nonatomic, strong) NSArray *imageArray;

@end

static NSString * const reuseIdentifier = @"Cell";

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.view.backgroundColor = [UIColor blackColor];
    
    self.imageArray = @[@"14", @"01", @"03", @"04", @"05", @"07", @"09", @"10", @"11", @"12", @"13", @"00"];
    
    HWCircleLayout *layout = [[HWCircleLayout alloc] init];
    
    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 100, [UIScreen mainScreen].bounds.size.width, 400) collectionViewLayout:layout];
    collectionView.dataSource = self;
    collectionView.backgroundColor = [UIColor whiteColor];
    collectionView.backgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"allen.jpg"]];
    collectionView.backgroundView.alpha = 0.5;
    [self.view addSubview:collectionView];
    self.collectionView = collectionView;
    
    [self.collectionView registerClass:[HWCollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];
}

#pragma mark <UICollectionViewDataSource>
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return self.imageArray.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    HWCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

    cell.imageView.image = [UIImage imageNamed: self.imageArray[indexPath.item]];
    
    return cell;
}

@end
           

HWCollectionViewCell：

#import <UIKit/UIKit.h>

@interface HWCollectionViewCell : UICollectionViewCell

@property (nonatomic, weak) UIImageView *imageView;

@end

#import "HWCollectionViewCell.h"

@implementation HWCollectionViewCell

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    
    if (self) {
        
        CGFloat w = [UIScreen mainScreen].bounds.size.width * 0.2;
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, w, w)];
        imageView.layer.cornerRadius = 10;
        imageView.layer.masksToBounds = YES;
        [self addSubview:imageView];
        self.imageView = imageView;
    }
    return self;
}

@end
           

HWCircleLayout：

#import <UIKit/UIKit.h>

@interface HWCircleLayout : UICollectionViewLayout

@end

#import "HWCircleLayout.h"

@implementation HWCircleLayout

//傳回YES，邊界發生改變，自動重新整理布局
-(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
    return YES;
}

//布局item屬性
-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    //建立執行個體
    UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
    
    CGFloat w = [UIScreen mainScreen].bounds.size.width * 0.2;
    //設定item的大小
    attributes.size = CGSizeMake(w, w);
    
    //設定圓的半徑
    CGFloat circleRadius = self.collectionView.frame.size.width * 0.35;
    
    //設定圓的中心點
    CGPoint circleCenter = CGPointMake(self.collectionView.frame.size.width * 0.5, self.collectionView.frame.size.height * 0.5);
    
    //計算每一個item之間的角度
    CGFloat itemAngle = M_PI * 2 / [self.collectionView numberOfItemsInSection:indexPath.section];
    
    //計算目前item的角度
    CGFloat currentAngle = indexPath.item * itemAngle;
    
    //計算目前item的中心
    CGFloat x = circleCenter.x + cos(currentAngle) * circleRadius;
    CGFloat y = circleCenter.y - sin(currentAngle) * circleRadius;
    
    //定位目前item的位置
    attributes.center = CGPointMake(x, y);
    
    //設定item的順序,越後面的顯示在前面
    attributes.zIndex = indexPath.item;
    
    return attributes;
}

//設定cell的布局屬性（包括item、header、footer）
-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSMutableArray *array = [NSMutableArray array];
    NSInteger count = [self.collectionView numberOfItemsInSection:0];
    
    //給每一個item建立并設定布局屬性
    for (int i = 0; i < count; i++) {
        //建立item的布局屬性
        UICollectionViewLayoutAttributes *attrs = [self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:0]];
        
        [array addObject:attrs];
    }
    return array;
}

@end
           

執行個體3，自定義UICollectionViewFlowLayout，實作書架效果如圖8-3：

下面貼上代碼：

ViewController：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end


#import "ViewController.h"
#import "HWBooksShelfFlowLayout.h"
#import "HWBooksShelfVC.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.view.backgroundColor = [UIColor blackColor];

    [self creatControl];
}

- (void)creatControl
{
    UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(50, 50, 100, 50)];
    [btn setTitle:@"進入書架" forState:UIControlStateNormal];
    [btn addTarget:self action:@selector(btnOnClick) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
}

- (void)btnOnClick
{
    HWBooksShelfFlowLayout *flowLayout = [[HWBooksShelfFlowLayout alloc] init];
    HWBooksShelfVC *vc = [[HWBooksShelfVC alloc] initWithCollectionViewLayout:flowLayout];
    [self presentViewController:vc animated:YES completion:nil];
}

@end
           

HWBooksShelfVC：

#import <UIKit/UIKit.h>

@interface HWBooksShelfVC : UICollectionViewController

@end


#import "HWBooksShelfVC.h"

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

@interface HWBooksShelfVC ()

@end

@implementation HWBooksShelfVC

static NSString * const reuseIdentifier = @"Cell";

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.collectionView.showsVerticalScrollIndicator = NO;
    self.collectionView.backgroundColor = [UIColor whiteColor];
    
    // Register cell classes
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];
}

#pragma mark <UICollectionViewDataSource>
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 20;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
    
    cell.backgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"cien"]];
    
    return cell;
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(mainW * 0.25, mainW * 0.308);
}

//cell的最小行間距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return mainW * 0.175;
}

//margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(0, mainW * 0.05, 0, mainW * 0.05);
}

//cell的最小列間距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    return mainW * 0.075;
}

//設定頂部的大小
-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
    return CGSizeMake(0, mainW * 0.16);
}

@end
           

HWBooksShelfFlowLayout：

#import <UIKit/UIKit.h>

@interface HWBooksShelfFlowLayout : UICollectionViewFlowLayout

@end


#import "HWBooksShelfFlowLayout.h"
#import "HWBooksShelfReusableView.h"

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

@implementation HWBooksShelfFlowLayout

- (void)prepareLayout
{
    [super prepareLayout];
    
    //注冊Decoration View
    [self registerClass:[HWBooksShelfReusableView class] forDecorationViewOfKind:@"HWBooksShelfReusableView"];
}

//Decoration View的布局
- (UICollectionViewLayoutAttributes *)layoutAttributesForDecorationViewOfKind:(NSString*)decorationViewKind atIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:decorationViewKind withIndexPath:indexPath];
    
    attributes.frame = CGRectMake(mainW * 0.026, mainW * 0.447 + mainW * 0.483 * indexPath.item, mainW * 0.948, mainW * 0.102);
    attributes.zIndex = -1;
    
    return attributes;
}

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSMutableArray *array = [NSMutableArray array];
    NSInteger count = [self.collectionView numberOfItemsInSection:0];
    
    for (int i = 0; i < count; i++) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
        [array addObject:[self layoutAttributesForDecorationViewOfKind:@"HWBooksShelfReusableView"atIndexPath:indexPath]];
    }
    
    for (int i = 0; i < count; i++) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
        [array addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
    }
    
    return array;
}

@end
           

HWBooksShelfReusableView：

#import <UIKit/UIKit.h>

@interface HWBooksShelfReusableView : UICollectionReusableView

@end


#import "HWBooksShelfReusableView.h"

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

@implementation HWBooksShelfReusableView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, mainW * 0.948, mainW * 0.102)];
        imageView.image = [UIImage imageNamed:@"decoration"];
        [self addSubview:imageView];
    }
    
    return self;
}

@end
           

執行個體4，自定義UICollectionViewFlowLayout，聚焦放大圖檔，如圖：

下面貼上代碼：

ViewController：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end


#import "ViewController.h"
#import "HWHorizontalFlowLayout.h"

#define mainW [UIScreen mainScreen].bounds.size.width
#define mainH [UIScreen mainScreen].bounds.size.height
#define KNum 10000

@interface ViewController ()<UICollectionViewDataSource, UICollectionViewDelegate>

@property (nonatomic, strong) NSArray *imageArray;
@property (nonatomic, strong) UICollectionView *collectionView;
@property (nonatomic, weak) UIPageControl *pageControl;

@end

@implementation ViewController

static NSString * const reuseIdentifier = @"flowLayoutTest";

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.view.backgroundColor = [UIColor whiteColor];
    
    _imageArray =  @[@"kbo", @"kbt", @"kbf"];
    
    //建立控件
    [self creatControl];
    
    //注冊辨別
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:reuseIdentifier];
    
    //初始化位置（設定為資料中間位置）
    [self.collectionView setContentOffset:CGPointMake(mainW * 0.65 * (_imageArray.count * KNum * 0.5 + 1), self.collectionView.contentOffset.y) animated:YES];
}

- (void)creatControl
{
    //collectionView
    _collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, mainW, mainH) collectionViewLayout:[[HWHorizontalFlowLayout alloc] init]];
    _collectionView.backgroundColor = [UIColor clearColor];
    _collectionView.showsVerticalScrollIndicator = NO;
    _collectionView.showsHorizontalScrollIndicator = NO;
    _collectionView.delegate = self;
    _collectionView.dataSource = self;
    [self.view addSubview:_collectionView];
    
    //pageControl
    UIPageControl *pageControl = [[UIPageControl alloc]initWithFrame:CGRectMake((mainW - 80) * 0.5, mainH - 100, 80, 30)];
    pageControl.numberOfPages = _imageArray.count;
    pageControl.currentPage = 1;
    pageControl.pageIndicatorTintColor = [UIColor lightGrayColor];
    pageControl.currentPageIndicatorTintColor = [UIColor blackColor];
    pageControl.userInteractionEnabled = NO;
    [self.view addSubview:pageControl];
    _pageControl = pageControl;
}

#pragma mark - UICollectionViewDataSource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    //傳回一個大資料，保證無限滾動
    return _imageArray.count * KNum;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
    
    cell.backgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:_imageArray[indexPath.item % _imageArray.count]]];
    
    return cell;
}

//點選事件
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"點選了圖檔%ld", indexPath.item % _imageArray.count);
    //do something...
}

//滑動事件
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //更新pageControl
    _pageControl.currentPage = (int)(scrollView.contentOffset.x / (mainW * 0.65)) % _imageArray.count;
}

@end
           

HWHorizontalFlowLayout：

#import <UIKit/UIKit.h>

@interface HWHorizontalFlowLayout : UICollectionViewFlowLayout

@end


#import "HWHorizontalFlowLayout.h"

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

@implementation HWHorizontalFlowLayout

- (instancetype)init
{
    if (self = [super init]) {
        self.minimumLineSpacing = 0;
        self.minimumInteritemSpacing = 0;
        self.itemSize = CGSizeMake(mainW * 0.65, mainW * 0.963);
        self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    }
    return self;
}

- (void)prepareLayout
{
    [super prepareLayout];
    
    CGFloat inset = (self.collectionView.frame.size.width - self.itemSize.width) * 0.5;
    self.sectionInset = UIEdgeInsetsMake(0, inset, 0, inset);
}

//邊界發生改變，是否重新整理布局，傳回YES時，重新重新整理布局調用layoutAttributesForElementsInRect方法
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
    return YES;
}

//設定cell的布局屬性，一個cell對應一個UICollectionViewLayoutAttributes對象
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSArray *array = [super layoutAttributesForElementsInRect:rect];
    
    //collectionView中心點的值
    CGFloat centerX = self.collectionView.frame.size.width * 0.5 + self.collectionView.contentOffset.x;
    
    //周遊更改
    for (UICollectionViewLayoutAttributes *atts in array) {
        //cell的中心點x和collectionView最中心點的x值的間距
        CGFloat space = ABS(atts.center.x - centerX);
        CGFloat scale = 1 - space/self.collectionView.frame.size.width * 0.2;
        atts.transform = CGAffineTransformMakeScale(scale, scale);
    }
    
    return array;
}

//這個方法的傳回值，就決定了collectionView停止滾動時的偏移量
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity
{
    //計算出最終顯示的矩形框
    CGRect rect;
    //最終要停下來的X
    rect.origin.x = proposedContentOffset.x;
    rect.origin.y = 0;
    rect.size = self.collectionView.frame.size;
    
    //獲得計算好的屬性
    NSArray *array = [super layoutAttributesForElementsInRect:rect];
    //計算collection中心點X
    CGFloat centerX = proposedContentOffset.x + self.collectionView.frame.size.width * 0.5;
    
    CGFloat minSpace = MAXFLOAT;
    for (UICollectionViewLayoutAttributes *attrs in array) {
        if (ABS(minSpace) > ABS(attrs.center.x - centerX)) {
            minSpace = attrs.center.x - centerX;
        }
    }
    //修改原有的偏移量
    proposedContentOffset.x += minSpace;
    
    return proposedContentOffset;
}

@end