一行iOS代码实现图片无限轮播器

时间:2017-06-02 21:49 来源:武松娱乐整理 字体:[ ] 评论:
最近一直在找实现图片无限轮播的方法,在网上也看了不少方法,大都不太合适,最终看到某IT培训公司一位讲师用 UICollectionView:一行代码实现图片无限轮播器的方法,当然想一行代码实现轮播功能,前期还是有一些工作要做。下面就把这个方法分享给大家! 一、图片无限轮播实现效果图:
图片无限轮播.gif 二、实现原理与分析: 假设有三张图片0、1、2,想要实现无限轮播,我们可以将UICollectionView的cell个数设为图片的个数 x 3,也就是把三张图片重复添加到9个cell中,可以把无限轮播分解成五种特殊的状态(五个临界点),轮播开始时为初始状态,在定时器的作用下依次滚动到最后一个cell,此时为右临界状态显示的是第2张图片,若想继续无缝滚动到第0图片,我们可以偷偷的将collectionView滚动到第三个cell上,可以看第四幅转态图此时显示的依然是第2张图片,这样再次滚动就是第0张图,这样就实现了cell向左滚动的无限循环轮播;向右滚动的原理一样,就是第三幅图到第五幅图的变化。
初始界状态.png
右临界状态.png
左临界状态.png
Paste_Image.png
Paste_Image.png 三、代码:
类文件.png
  1.  JFWeakTimerTargetObject继承自NSObject
  2. JFLoopView继承自UIView
  3. JFLoopViewCell继承自UICollectionViewCell
  4. JFLoopViewLayout继承自UICollectionViewFlowLayout
  5. JFMainViewController继承自UIViewController
JFWeakTimerTargetObject重写定时器NSTimer的+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo;类方法的目的是:避免当定时器强引用JFLoopView类,JFLoopView无法被释放的问题。
JFWeakTimerTargetObject.h文件
#import <Foundation/Foundation.h> @interface JFWeakTimerTargetObject : NSObject + (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo; @end
JFWeakTimerTargetObject.m文件
#import "JFWeakTimerTargetObject.h" @interface JFWeakTimerTargetObject () @property (nonatomic, weak) id target; @property (nonatomic, assign) SEL selector; @end @implementation JFWeakTimerTargetObject + (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo { //创建当前类对象 JFWeakTimerTargetObject *object = [[JFWeakTimerTargetObject alloc] init]; object.target = aTarget; object.selector = aSelector; return [NSTimer scheduledTimerWithTimeInterval:ti target:object selector:@selector(fire:) userInfo:userInfo repeats:yesOrNo]; } - (void)fire:(id)obj { [self.target performSelector:self.selector withObject:obj]; } @end
JFLoopView.h文件
#import <UIKit/UIKit.h> @interface JFLoopView : UIView //JFLoopView初始化方法 - (instancetype)initWithImageArray:(NSArray *)imageArray; @end
JFLoopView.m文件
#import "JFLoopView.h" #import "JFLoopViewLayout.h" #import "JFLoopViewCell.h" #import "JFWeakTimerTargetObject.h" @interface JFLoopView () <UICollectionViewDelegate, UICollectionViewDataSource> @property (nonatomic, strong) UICollectionView *collectionView; @property (nonatomic, strong) UIPageControl *pageControl; @property (nonatomic, strong) NSArray *imageArray; @property (nonatomic, weak) NSTimer *timer; @end static NSString *ID = @"loopViewCell"; @implementation JFLoopView - (instancetype)initWithImageArray:(NSArray *)imageArray { if (self = [super init]) { UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:[[JFLoopViewLayout alloc] init]]; [collectionView registerClass:[JFLoopViewCell class] forCellWithReuseIdentifier:ID]; collectionView.dataSource = self; collectionView.delegate = self; [self addSubview:collectionView]; self.collectionView = collectionView; self.imageArray = imageArray; //添加分页器 [self addSubview:self.pageControl]; //回到主线程刷新UI dispatch_async(dispatch_get_main_queue(), ^{ //设置滚动的初始状态在 [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:self.imageArray.count inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:NO]; //添加定时器 [self addTimer]; }); } return self; } /// 懒加载pageControl - (UIPageControl *)pageControl { if (!_pageControl) { _pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, 220, 0, 30)]; _pageControl.numberOfPages = self.imageArray.count; _pageControl.pageIndicatorTintColor = [UIColor orangeColor]; _pageControl.currentPageIndicatorTintColor = [UIColor purpleColor]; } return _pageControl; } #pragma mark --- UICollectionViewDataSource 数据源方法 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { return self.imageArray.count * 3; } - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { JFLoopViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:ID forIndexPath:indexPath]; cell.imageName = self.imageArray[indexPath.item % self.imageArray.count]; return cell; } #pragma mark ---- UICollectionViewDelegate /// 滚动完毕就会调用(如果不是人为拖拽scrollView导致滚动完毕,才会调用这个方法) - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView { [self scrollViewDidEndDecelerating:scrollView]; } /// 当滚动减速时调用 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { CGFloat offsetX = scrollView.contentOffset.x; NSInteger page = offsetX / scrollView.bounds.size.width; //手动滚动到左边临界状态 if (page == 0) { page = self.imageArray.count; self.collectionView.contentOffset = CGPointMake(page * scrollView.frame.size.width, 0); //滚动到右临界状态 }else if (page == [self.collectionView numberOfItemsInSection:0] - 1) { page = self.imageArray.count - 1; self.collectionView.contentOffset = CGPointMake(page * scrollView.frame.size.width, 0); } //设置UIPageControl当前页 NSInteger currentPage = page % self.imageArray.count; self.pageControl.currentPage =currentPage; //添加定时器 [self addTimer]; } ///手指开始拖动时调用 - (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView { //移除定时器 [self removeTimer]; } /// 添加定时器 - (void)addTimer { if (self.timer) return; self.timer = [JFWeakTimerTargetObject scheduledTimerWithTimeInterval:1.5 target:self selector:@selector(nextImage) userInfo:nil repeats:YES]; [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes]; } /// 移除定时器 - (void)removeTimer { [self.timer invalidate]; self.timer = nil; } /// 切换到下一张图片 - (void)nextImage { CGFloat offsetX = self.collectionView.contentOffset.x; NSInteger page = offsetX / self.collectionView.bounds.size.width; [self.collectionView setContentOffset:CGPointMake((page + 1) * self.collectionView.bounds.size.width, 0) animated:YES]; } - (void)layoutSubviews { [super layoutSubviews]; self.collectionView.frame = self.bounds; } - (void)dealloc { [self removeTimer]; } @end
JFLoopViewCell.h文件
#import <UIKit/UIKit.h> @interface JFLoopViewCell : UICollectionViewCell @property (nonatomic, copy) NSString *imageName; @end
JFLoopViewCell.m文件
#import "JFLoopViewCell.h" @interface JFLoopViewCell () @property (nonatomic, weak) UIImageView *iconView; @end @implementation JFLoopViewCell - (instancetype)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { UIImageView *iconView = [[UIImageView alloc] init]; [self addSubview:iconView]; self.iconView = iconView; } return self; } - (void)setImageName:(NSString *)imageName { _imageName = imageName; self.iconView.image = [UIImage imageNamed:imageName]; } - (void)layoutSubviews { [super layoutSubviews]; self.iconView.frame = self.bounds; } @end
JFLoopViewLayout.h文件
#import <UIKit/UIKit.h> @interface JFLoopViewLayout : UICollectionViewFlowLayout @end
JFLoopViewLayout.m文件
#import "JFLoopViewLayout.h" @implementation JFLoopViewLayout /// 准备布局 - (void)prepareLayout { [super prepareLayout]; //设置item尺寸 self.itemSize = self.collectionView.frame.size; //设置滚动方向 self.scrollDirection = UICollectionViewScrollDirectionHorizontal; //设置分页 self.collectionView.pagingEnabled = YES; //设置最小间距 self.minimumLineSpacing = 0; self.minimumInteritemSpacing = 0; //隐藏水平滚动条 self.collectionView.showsHorizontalScrollIndicator = NO; } @end
JFMainViewController.h文件
#import <UIKit/UIKit.h> @interface JFMainViewController : UIViewController @end
JFMainViewController.m文件
#import "JFMainViewController.h" #import "JFLoopView.h" @interface JFMainViewController () @property (nonatomic, strong) JFLoopView *loopView; @end @implementation JFMainViewController - (void)viewDidLoad { [super viewDidLoad]; //关闭自动调整滚动视图 self.automaticallyAdjustsScrollViewInsets = NO; } - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.navigationController.navigationBar.hidden = YES; } - (void)loadView { [super loadView]; //设置图片数据 NSArray *imageArray = @[@"srcoll_01",@"srcoll_02",@"srcoll_03"]; //此行代码实现无限轮播 _loopView = [[JFLoopView alloc] initWithImageArray:imageArray]; //设置loopView的frame _loopView.frame = CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 250); [self.view addSubview:self.loopView]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } @end
注意:如果你的控制器有UINavigationBar,且隐藏了navigationBar,一定要记得设置self.automaticallyAdjustsScrollViewInsets = NO; automaticallyAdjustsScrollViewInsets是干嘛的呢?简单点说就是automaticallyAdjustsScrollViewInsets根据所在界面的status bar、navigationbar、与tabbar的高度,自动调整scrollview的 inset,设置为NO,不让viewController调整,我们自己修改布局即可。如果不设置为NO就可能出现下面的情况,自动滚动和拖动的时候imageView的位置会变化。

图片无限轮播bug展示.gif 四、总结: 1、实现无限轮播器的主要控件是UICollectionView和UIPageControl,
2、封装好工具类以后再使用时一行_loopView = [[JFLoopView alloc] initWithImageArray:imageArray];代码,然后设置frame就可以复用无限轮播器。
3、合理切换图片和图片排列的方法,加上恰当地使用UICollectionView提供的代理方法就可以完美的实现无限轮播器。
写在最后: 下一篇文章讲用UICollectionView实现电商APP首页的方法:

电商APP的首页展示.gif
如果你有好的方法敬请分享,感谢你的阅读!欢迎关注和评论! 源码地址:链接: https://pan.baidu.com/s/1nv5FqZJ 密码: qz3u 以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持武松娱乐。
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