//
// 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(shè)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(diào)用cell.img = img的時候回調(diào)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"
//定義宏圖片的個數(shù)
#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(shù)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(zhì)就是改變cell的索引,再根據(jù)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(zhí)行,為了不讓連續(xù)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