iOS 超简单无限轮播

简介##

现在的公司项目基本上都会要求来一两个无限轮播,可是如何才能够把这个无限轮播写好了,看着挺简单的,加上一个定时器走你.我以前用ScrollView写过一个无限轮播,发现在只有两条数据的时候左右拖动是会有问题,并且逻辑还非常的复杂,今天就给大家分享一个简单的无限轮播方法.

毫无疑问,要想让图片自己不停的切换,需要使用到定时器,为了方便使用,我在这里给定时器写了一个分类.通过定时器的暂停和恢复来实现轮播图的暂停和恢复.

#import "NSTimer+addition.h"

@implementation NSTimer (addition)
/// 暂停
- (void)pause {
    if (!self.isValid) return;
    [self setFireDate:[NSDate distantFuture]];
}
/// 恢复
- (void)resume {
    if (!self.isValid) return;
    [self setFireDate:[NSDate date]];
}
/// 多少秒后恢复
- (void)resumeWithTimeInterval:(NSTimeInterval)time {
    if (!self.isValid) return;
    [self setFireDate:[NSDate dateWithTimeIntervalSinceNow:time]];
}

@end

要诀 使用UITableView或者UICollectionView来做无限轮播,然后设置在其代理方法返回有多少rows的时候返回一个巨大的数字.上面顶部的banner滚动条就是用UICollectionView做的,接下来我会着重讲使用UICollectionView的无限轮播做法,UITableView类似.

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { 
    // 在这里返回一个比较大的数字
    return  5000000;
}

我的轮播视图WYLoopView.h

// 点击了轮播图的block
typedef void(^TapAction)(UIImage *image);

@interface WYLoopView : UIView

@property (nonatomic, strong) NSArray *dataSource;

- (instancetype)initWithFrame:(CGRect)frame tapAction:(TapAction)action;

// 恢复
- (void)resume;
// 暂停
- (void)pause;

@end

WYLoopView.m我设置了当只有一个图的时候不让其滚动,最少两张图才可以滚动.

#import "WYLoopView.h"
#import "NSTimer+addition.h"
#import "UIImageView+WebCache.h"

#define INDEX indexPath.item % _dataSource.count

static NSString *const kReuseId = @"LoopCell";
static NSInteger const kMaxCount = 1000000;
static NSTimeInterval const kTimeInterval = 1.0;

////////////////////////////////////  WYLoopCell  ////////////////////////
@interface WYLoopCell : UICollectionViewCell
@property (nonatomic, copy) NSString *url;
@end

@implementation WYLoopCell
{
    UIImageView *_imageView;
}

- (void)setURL:(NSString *)url {
    _url = url;
    
    [_imageView sd_setImageWithURL:[NSURL URLWithString:url] placeholderImage:[UIImage imageNamed:@"ic_home_banner_defult.png"]];
}

- (instancetype)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        [self setupUI];
    }
    return self;
}

- (void)setupUI {
    _imageView = [[UIImageView alloc] initWithFrame:self.contentView.bounds];
    [self.contentView addSubview:_imageView];
}

@end

////////////////////////////////////  WYLoopView  ////////////////////////
@interface WYLoopView ()<UICollectionViewDataSource, UICollectionViewDelegate>
@end
@implementation WYLoopView
{
    UICollectionView *_collectionView;
    UIPageControl    *_pageControl;
    NSTimer          *_timer;
    TapAction        _action;
    NSInteger        _currentPage;
}

- (instancetype)initWithFrame:(CGRect)frame tapAction:(TapAction)action {
    if (self = [super initWithFrame:frame]) {
        _action = action;
        [self initialTimer];
        [self setupUI];
    }
    return self;
}

- (void)dealloc {
    [_timer invalidate];
    _timer = nil;
}

- (void)pause {
    [_timer pause];
}

- (void)resume {
    [_timer resumeWithTimeInterval:kTimeInterval];
}

#pragma mark - setter
- (void)setDataSource:(NSArray *)dataSource {
    [_timer pause];
    _dataSource = dataSource;
    
    _pageControl.numberOfPages = _dataSource.count > 1 ?_dataSource.count:0;
    [_collectionView reloadData];
    
    _pageControl.currentPage = 0;

    if (_dataSource.count < 2) return;
    
    [_collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:_dataSource.count * 10 inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:NO];
    _currentPage = _dataSource.count * 10;
    [_timer resumeWithTimeInterval:kTimeInterval];
}

#pragma mark - NSTimer
- (void)initialTimer {
    _timer = [NSTimer scheduledTimerWithTimeInterval:kTimeInterval target:self selector:@selector(nextPage:) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:_timer forMode:NSRunLoopCommonModes];
    [_timer pause];
}
- (void)nextPage:(NSTimer *)timer {
    if (_dataSource.count < 2) return;
    [_collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:++_currentPage inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];
    
    _pageControl.currentPage = _currentPage % _dataSource.count;
}

#pragma mark - setupUI
- (void)setupUI {
    [self prepareCollectionView];
    [self preparePageControl];
    
    [self addSubview:_collectionView];
    [self addSubview:_pageControl];
    
    UIImageView *logoView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 26, 55, 25)];
    logoView.image = [UIImage imageNamed:@"ic_home_logo"];
    [self addSubview:logoView];
}

- (void)prepareCollectionView {
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    flowLayout.itemSize = self.bounds.size;
    flowLayout.minimumInteritemSpacing = 0;
    flowLayout.minimumLineSpacing = 0;
    flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    
    _collectionView = [[UICollectionView alloc] initWithFrame:self.bounds collectionViewLayout:flowLayout];
    _collectionView.dataSource = self;
    _collectionView.delegate = self;
    _collectionView.pagingEnabled = YES;
    _collectionView.showsHorizontalScrollIndicator = NO;
    
    // 注册cell
    [_collectionView registerClass:[WYLoopCell class] forCellWithReuseIdentifier:kReuseId];
}

- (void)preparePageControl {
    _pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake((SCREEN_WIDTH - 100) * 0.5, self.bounds.size.height - 17, 100 , 5)];
    _pageControl.numberOfPages = _dataSource.count;
//    _pageControl.currentPageIndicatorTintColor = [UIColor greenColor];
//    _pageControl.pageIndicatorTintColor = [UIColor orangeColor];
}

#pragma mark - UICollectionViewDataSource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return _dataSource.count > 1 ?  kMaxCount : _dataSource.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    WYLoopCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kReuseId forIndexPath:indexPath];
    cell.url = _dataSource[INDEX];
    return cell;
}

#pragma mark - UICollectionViewDelegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    if (!_action) return;
    _action(_dataSource[INDEX]);
}

#pragma mark - UIScrollViewDelegate
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    _currentPage = scrollView.contentOffset.x / SCREEN_WIDTH;
    
    _pageControl.currentPage = _currentPage % _dataSource.count;
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    [_timer pause];
}

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    [_timer resumeWithTimeInterval:kTimeInterval];
}

@end