效果图
本文gitoschia的地址
https://git.oschina.net/mark6/scrollLoop.git
本文gitHub地址
https://github.com/markdashi/scrollLoop
上一周在简书首页投稿看到了很多关于轮播图的文章，每一篇我都点进去看了一下，很可惜我看到的都是基于ScrollView的封装，好一点的会考虑到复用，就是放3个imageView来实现的图片的轮播，加上定时器。我很不理解的是，既然能考虑到复用的朋友为什么没有考虑到UICollecionView呢？好吧，我暂且相信你对UICollecionView不太熟悉，现在我将自己的思路及实现分享一下，供有兴趣的朋友参考一下。
首先我说一下UICollecionView的优点
1.首先不需要考虑复用，在整个过程中只会创建两个cell.
2.性能高，通用性强。
其次说一下实现的主要思路，
继承UIView定义一个scrollLoopView类，将UICollecionView添加到整个类subViews,定义数据源为传进来数组 * 10，开始定义collectionView为其中心位置，当滑动index超过数据源count时让它又从中心开始。当然这只是一个简单的思路，中间会有很多小细节处理，具体看代码。
#import <UIKit/UIKit.h>
@class scrollLoopView;
@protocol scrollLoopViewDelegate <NSObject>
@optional
- (void)scrollLoopView:(scrollLoopView *)scrollLoopView didSelectItemAtIndex:(int)index;
@end
@class scrollLoopViewDelegate;
@interface scrollLoopView : UIView
@property (nonatomic, strong) NSArray *images;
@property (nonatomic, weak) id<scrollLoopViewDelegate>delegate;
@end
在其initWithFrame写相应的配置
- (instancetype)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
[self initsConfig];
}
return self;
}
/**
* 配置基本框架
*/
- (void)initsConfig
{
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
layout.minimumLineSpacing = 0;
layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
_flowLayout = layout;
UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:self.bounds collectionViewLayout:layout];
collectionView.backgroundColor = [UIColor clearColor];
collectionView.delegate = self;
collectionView.dataSource = self;
collectionView.pagingEnabled = YES;
collectionView.showsHorizontalScrollIndicator = NO;
[collectionView registerNib:[UINib nibWithNibName:@"MyCollectionViewCell" bundle:[NSBundle mainBundle]] forCellWithReuseIdentifier:identify];
_collectionView = collectionView;
[self addSubview:collectionView];
UIPageControl *pageControl = [[UIPageControl alloc] init];
_pageControl = pageControl;
[self addSubview:pageControl];
}
这里一定要注意的是，在layoutSubView中，定义_flowLayout.itemSize尺寸，否则会报错。
- (void)layoutSubviews
{
[super layoutSubviews];
_flowLayout.itemSize = self.frame.size;
_collectionView.frame = self.bounds;
//这里是为了collection起始位置居中，而animated一定为NO,否则你会遇到你不想要效果
if (_collectionView.contentOffset.x == 0 && _totalImageCount) {
int tarIndex = _totalImageCount * 0.5;
[_collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:tarIndex inSection:0] atScrollPosition:UICollectionViewScrollPositionNone animated:NO];
}
//_pageControl 的frame是相对固定的
_pageControl.frame = CGRectMake((self.frame.size.width - 100)/2, self.frame.size.height - 30, 100, 20);
}
实现自动轮播少不了的是定时器NSTimer
- (void)setupTimer{
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:NSTimeIntervalDefault target:self selector:@selector(AutoScroll) userInfo:nil repeats:YES];
_timer = timer;
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
}
- (void)AutoScroll
{
int currentIndex = [self currentIndex];
int targetIndex = currentIndex + 1;
if (targetIndex >= _totalImageCount) {
targetIndex = _totalImageCount * 0.5;
[_collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:targetIndex inSection:0] atScrollPosition:UICollectionViewScrollPositionNone animated:NO];
return;
}
[_collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:targetIndex inSection:0] atScrollPosition:UICollectionViewScrollPositionNone animated:YES];
}
//当前第几页
- (int)currentIndex{
if (_collectionView.frame.size.width == 0) {
return 0;
}
int index = 0;
index = (_collectionView.contentOffset.x + _flowLayout.itemSize.width * 0.5) /_flowLayout.itemSize.width;
return index;
}
而定时器在哪里添加呢？？？有心的朋友可以不往下看，自己独立思考一下。
- (void)setImages:(NSArray *)images
{
_images = images;
_totalImageCount = _images.count *10;
if (images.count != 1) {
[self setupTimer];
_pageControl.numberOfPages = images.count;
}
[_collectionView reloadData];
}
//当设置数据源的时候，只要传进来的数据不为空，就设置定时器
接下来最最要的UICollectionView的代理方法
#pragma mark - UICollectionViewDataSource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return _totalImageCount;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
MyCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identify forIndexPath:indexPath];
long index = indexPath.item % self.images.count;
[cell.imageView sd_setImageWithURL:[NSURL URLWithString:self.images[index]]];
cell.label.text = [NSString stringWithFormat:@"%zd",index];
return cell;
}
大家看代码，可以发现上面主要的加载的是网络图片，当然你可以判断传进来数组中字符串的类型，如果是本地，就采用imageNamed方法来加载
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
MyCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identify forIndexPath:indexPath];
long index = indexPath.item % self.images.count;
cell.label.text = [NSString stringWithFormat:@"%zd",index];
if (![self.images[index] hasPrefix:@"http"]) {
cell.imageView.image =[UIImage imageNamed:self.images[index]];
return cell;
}
[cell.imageView sd_setImageWithURL:[NSURL URLWithString:self.images[index]]];
return cell;
}
点击的相应事件如下处理
#pragma mark - UICollectionViewDelegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
if ([self.delegate respondsToSelector:@selector(scrollLoopView:didSelectItemAtIndex:)]) {
[self.delegate scrollLoopView:self didSelectItemAtIndex:(int)indexPath.item % self.images.count];
}
}
pageControl联动
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
int index = [self currentIndex];
_pageControl.currentPage = index % self.images.count;
}
这样呢我们这个类就简单的封装好了，使用起来更加简单,那个类使用，导入头文件
scrollLoopView *loop = [[scrollLoopView alloc] initWithFrame:CGRectMake(0, 64, SCREENWIDTH, 300)];
loop.delegate = self;
loop.images =@[ @"http://web.img.chuanke.com/fragment/9d595bc8fb5bf049ce3db527ede08abc.jpg",
@"http://web.img.chuanke.com/fragment/d662adfaebdc9aa3dac4b04299aa48e1.jpg",
@"http://web.img.chuanke.com/fragment/8003092be7e6cc3222c760c89e74a20d.jpg",
];
[self.view addsubView:loop];
优化部分
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
[self invalidateTimer];
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
[self setupTimer];
}
//确保定时器不出错
以上呢就是轮播的简单的实现，博主呢主要目的是给敢兴趣的朋友提一个主要思路，供大家参考，当然这个类优化的空间很大，可扩展的空间也很大，有好的建议的伙伴可以尽管留言。
