iOS项目开发之实现无限轮播

简介

分析

实现

代码下载

一、简介

在实际的开发当中，会经常有界面需要实现图片的无限轮播这样的需求。比如新闻app，或者其他app的广告位

实现的方式有很多种，最先想动的一定是scrollView，但是其实scrollView实现起来并没有那么容易。这里，我用了一个较为取巧的办法，使用UICollectionView来实现无限轮播

二、分析

无限轮播，通常就是图片的无限循环的播放。当到最后一个图片的时候，再次轮播时，显示第一个图片。

UICollectionView可以进行上下滚动，也可以进行左右滚动，所有这里我们只需要使用它，并且让它左右滚动即可

我这里将整个内容封装到一个View里面，使用起来较为简单，另外代码中注释也很清晰，这里不做阐述。

三、实现

1⃣️在主控制器中创建广告位

/**
*  加载数据
*/
- (void)loadData
{
NSURL *dataUrl = [[NSBundle mainBundle] URLForResource:@"newses.plist" withExtension:nil];
NSArray *data = [NSArray arrayWithContentsOfURL:dataUrl];
NSMutableArray *tempArray = [NSMutableArray array];
for (NSDictionary *dict in data) {
AdvertModel *advert = [AdvertModel advertModelWithDict:dict];
[tempArray addObject:advert];
}
_advertData = tempArray;
}

- (void)createAdvertView
{
CGRect advertRect = CGRectMake(10, 40, 300, 130);
AdvertView *advertView = [[AdvertView alloc] initWithFrame:advertRect];
advertView.advertData = _advertData;
[self.view addSubview:advertView];
}

2⃣️广告位的View的实现

#import "AdvertView.h"
#import "AdvertModel.h"
#import "AdvertCell.h"

#define cellIdentifier @"advertcell"

@interface AdvertView() <UICollectionViewDataSource, UICollectionViewDelegate>
{
UICollectionView *_advertView;
UIPageControl *_pageControl;

NSTimer *_timer;

NSInteger _width;
NSInteger _height;
}
@end

@implementation AdvertView

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
//1.设置宽高
_width = frame.size.width;
_height = frame.size.height;

//2.创建广告位和PageControl
[self createAdvertView];
[self createPageView];

//3.创建定时器
[self addTimer];
}
return self;
}

/**
*  加载数据
*/
- (void)setAdvertData:(NSArray *)advertData
{
_advertData = advertData;
[_advertView reloadData];

[_advertView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:100 inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:NO];
}

/**
*  创建广告位
*/
- (void)createAdvertView
{
UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
flowLayout.minimumLineSpacing = 0;
flowLayout.minimumInteritemSpacing = 0;
flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
flowLayout.itemSize = CGSizeMake(_width, _height);

CGRect advertRect = CGRectMake(0, 0, _width, _height);
_advertView = [[UICollectionView alloc] initWithFrame:advertRect collectionViewLayout:flowLayout];
[_advertView registerClass:[AdvertCell class] forCellWithReuseIdentifier:cellIdentifier];
_advertView.delegate = self;
_advertView.dataSource = self;
_advertView.pagingEnabled = YES;
_advertView.showsHorizontalScrollIndicator = NO;
_advertView.showsVerticalScrollIndicator = NO;
[self addSubview:_advertView];
}

/**
*  创建页码的View
*/
- (void)createPageView
{
UIPageControl *pageControl = [[UIPageControl alloc] init];
pageControl.center = CGPointMake(self.frame.size.width * 0.5, _height - 20);
pageControl.bounds = CGRectMake(0, 0, 100, 0);
pageControl.numberOfPages = 5;
pageControl.pageIndicatorTintColor = [UIColor blueColor];
pageControl.currentPageIndicatorTintColor = [UIColor redColor];
[self addSubview:pageControl];
_pageControl = pageControl;
}

/**
*  添加定时器
*/
- (void)addTimer
{
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextAdvert) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
_timer = timer;
}
/**
*  删除定时器
*/
- (void)removeTimer
{
[_timer invalidate];
_timer = nil;
}

/**
*  下一个广告
*/
- (void)nextAdvert
{
CGFloat offset = _advertView.contentOffset.x + _width;
[_advertView setContentOffset:CGPointMake(offset, 0) animated:YES];
}

#pragma mark - UICollectionView的数据源和代理方法

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
//这里将数据放足够大，可以无限的轮播循环
return _advertData.count * 1000;
}

- (AdvertCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
AdvertCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
cell.advert = _advertData[indexPath.item % 5];
return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
{
//取出当前可见的单元格
NSIndexPath *visiablePath = [[collectionView indexPathsForVisibleItems] firstObject];
_pageControl.currentPage = visiablePath.item % 5;
}

#pragma mark 当拖拽时，暂时将定时器销毁
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
[self removeTimer];
}
#pragma mark 停止拖拽时，再次创建定时器
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
[self addTimer];
}

@end

四、代码下载地址

https://github.com/wangzi9521/InfinitePicture