//// PBCollectionCell.h// 無限滾動//// Created by 裴波波 on 16/3/30.// Copyright © 2016年 裴波波. All rights reserved.//#import <UIKit/UIKit.h>@interface PBCollectionCell : UICollectionViewCell@property(nonatomic,strong)UIImage * img;@end•cell.m文件//// PBCollectionCell.m// 無限滾動//// Created by 裴波波 on 16/3/30.// Copyright © 2016年 裴波波. All rights reserved.//#import "PBCollectionCell.h"@interface PBCollectionCell ()//不要忘記給collectionView的cell上設置圖片框,并拖線到cell分類中@property (strong, nonatomic) IBOutlet UIImageView *imgView;@end@implementation PBCollectionCell//重寫img的set方法來個cell進行賦值.(當調用cell.img = img的時候回調用set ..img的方法)-(void)setImg:(UIImage *)img{_img = img;self.imgView.image = img;}@end

//// ViewController.m// 無限滾動//// Created by 裴波波 on 16/3/30.// Copyright © 2016年 裴波波. All rights reserved.//#import "ViewController.h"#import "PBCollectionCell.h"http://定義宏圖片的個數#define kPictureCount 3@interface ViewController ()@property (strong, nonatomic) IBOutlet UICollectionViewFlowLayout *flowLayout;/*** 圖片的索引*/@property(nonatomic,assign) NSInteger index;@end•聲明全局變量index為了拼接滾動過程中切換的圖片的索引@implementation ViewController-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{return kPictureCount;}-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{static NSString * ID = @"cell";PBCollectionCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:ID forIndexPath:indexPath];//圖片索引只有下一站或者上一張,即+1,或者-1,為了切換圖片//中間的cell的腳標是1,滾動后腳標是2或者0,湊成next值為+1或者-1(讓圖片索引+1或者-1來完成切換圖片),則NSInteger next = indexPath.item - 1;//為了不讓next越界,進行取余運算 ---------+next為了切換圖片next = (self.index + kPictureCount + next) % kPictureCount;NSString * imgName = [NSString stringWithFormat:@"%02ld",next + 1];UIImage * img = [UIImage imageNamed:imgName];cell.img = img;return cell;}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{//計算偏移的整數倍,偏移了0或者是2, -1是讓self.index圖片索引+1 或者 -1以切換圖片;NSInteger offset = scrollView.contentOffset.x / scrollView.bounds.size.width - 1;self.index = (offset + self.index + kPictureCount) % kPictureCount;//本質就是改變cell的索引,再根據self.index來切換圖片,使用取余讓圖片索引不至于越界//異步主隊列執行,為了不讓連續滾動停止后,圖片有閃動.dispatch_async(dispatch_get_main_queue(), ^{[self scrollToSecondCell];});}

-(void)scrollToSecondCell{NSIndexPath * idxPath = [NSIndexPath indexPathForItem:1 inSection:0];[self.collectionView scrollToItemAtIndexPath:idxPath atScrollPosition:UICollectionViewScrollPositionLeft animated:NO];}- (void)viewDidLoad {[super viewDidLoad];self.flowLayout.itemSize = self.collectionView.bounds.size;self.flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;self.flowLayout.minimumLineSpacing = 0;self.collectionView.backgroundColor = [UIColor whiteColor];self.collectionView.pagingEnabled = YES;self.collectionView.bounces = NO;self.collectionView.showsHorizontalScrollIndicator = NO;[self scrollToSecondCell];}@end