UI-图片轮播器
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效果图
LoopView.h
1 #import <UIKit/UIKit.h> 2 3 @interface LoopView : UICollectionView 4 5 - (instancetype)initWithUrls:(NSArray <NSURL *> *)urls didSelectedIndex:(void (^)(NSInteger index))selectedIndex; 6 7 @end
LoopView.m
1 #import "LoopView.h" 2 #import "LoopViewFlowLayout.h" 3 #import "LoopViewCell.h" 4 5 NSString *const LoopViewCellIdentifier = @"LoopViewCellIdentifier"; 6 7 @interface LoopView() <UICollectionViewDataSource, UICollectionViewDelegate> 8 @property (nonatomic, copy) void (^selectedCallBack)(NSInteger index); 9 @end 10 11 @implementation LoopView { 12 NSArray <NSURL *> *_urls; 13 } 14 15 - (instancetype)initWithUrls:(NSArray <NSURL *> *)urls didSelectedIndex:(void (^)(NSInteger))selectedIndex { 16 self = [super initWithFrame:CGRectZero collectionViewLayout:[LoopViewFlowLayout new]]; 17 if (self) { 18 _urls = urls; 19 _selectedCallBack = selectedIndex; 20 21 self.dataSource = self; 22 self.delegate = self; 23 24 [self registerClass:[LoopViewCell class] forCellWithReuseIdentifier:LoopViewCellIdentifier]; 25 26 // 滚动到第 count 的位置 27 if (_urls.count > 1) { 28 dispatch_async(dispatch_get_main_queue(), ^{ 29 NSIndexPath *indexPath = [NSIndexPath indexPathForItem:_urls.count inSection:0]; 30 31 [self scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:NO]; 32 }); 33 } 34 } 35 return self; 36 } 37 38 #pragma mark - UICollectionViewDataSource 39 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { 40 // 如果只有一张图片,不滚动,否则显示 2 倍 的图像 41 return _urls.count * (_urls.count == 1 ? 1 : 100); 42 } 43 44 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { 45 46 LoopViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:LoopViewCellIdentifier forIndexPath:indexPath]; 47 48 cell.url = _urls[indexPath.item % _urls.count]; 49 50 return cell; 51 } 52 53 /// 滚动视图停止滚动 54 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { 55 NSInteger offset = scrollView.contentOffset.x / scrollView.bounds.size.width; 56 57 // 判断是否是第0页和最后一页 58 if (offset == 0 || offset == ([self numberOfItemsInSection:0] - 1)) { 59 60 // 第 0 页,切换到 count 位置,最后一页,切换到 count - 1 的位置 61 offset = _urls.count - (offset == 0 ? 0 : 1); 62 63 // 调整 offset 64 scrollView.contentOffset = CGPointMake(offset * scrollView.bounds.size.width, 0); 65 } 66 } 67 68 - (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath { 69 if (_selectedCallBack != nil) { 70 _selectedCallBack(indexPath.item % _urls.count); 71 } 72 } 73 74 @end
LoopViewFlowLayout.m
1 #import "LoopViewFlowLayout.h" 2 3 @implementation LoopViewFlowLayout 4 5 - (void)prepareLayout { 6 [super prepareLayout]; 7 8 self.itemSize = self.collectionView.bounds.size; 9 self.minimumLineSpacing = 0; 10 self.minimumInteritemSpacing = 0; 11 self.scrollDirection = UICollectionViewScrollDirectionHorizontal; 12 13 self.collectionView.pagingEnabled = YES; 14 self.collectionView.bounces = NO; 15 self.collectionView.showsVerticalScrollIndicator = NO; 16 self.collectionView.showsHorizontalScrollIndicator = NO; 17 } 18 19 @end
LoopViewCell.h
1 #import <UIKit/UIKit.h> 2 3 @interface LoopViewCell : UICollectionViewCell 4 5 @property (nonatomic) NSURL *url; 6 7 @end
LoopViewCell.m
1 #import "LoopViewCell.h" 2 3 @implementation LoopViewCell { 4 UIImageView *_imageView; 5 } 6 7 - (instancetype)initWithFrame:(CGRect)frame { 8 self = [super initWithFrame:frame]; 9 if (self) { 10 _imageView = [[UIImageView alloc] initWithFrame:self.bounds]; 11 [self.contentView addSubview:_imageView]; 12 } 13 return self; 14 } 15 16 - (void)setUrl:(NSURL *)url { 17 _url = url; 18 19 NSData *data = [NSData dataWithContentsOfURL:url]; 20 _imageView.image = [UIImage imageWithData:data]; 21 } 22 23 @end
ViewController.m
1 #import "ViewController.h" 2 #import "LoopView.h" 3 4 @interface ViewController () 5 6 @end 7 8 @implementation ViewController { 9 NSArray <NSURL *> *_urls; 10 } 11 12 - (void)viewDidLoad { 13 [super viewDidLoad]; 14 15 // 1. 加载数据 16 [self loadData]; 17 18 // 2. 图片轮播器视图 19 LoopView *loopView = [[LoopView alloc] initWithUrls:_urls didSelectedIndex:^(NSInteger index) { 20 }]; 21 22 CGFloat width = self.view.bounds.size.width; 23 loopView.frame = CGRectMake(20, width / 2, width - 40, 200); 24 [self.view addSubview:loopView]; 25 } 26 27 - (void)loadData { 28 NSMutableArray *array = [NSMutableArray array]; 29 30 for (int i = 0; i < 3; i++) { 31 NSString *fileName = [NSString stringWithFormat:@"%02zd.jpg", (i + 1)]; 32 NSURL *url = [[NSBundle mainBundle] URLForResource:fileName withExtension:nil]; 33 34 [array addObject:url]; 35 } 36 _urls = array.copy; 37 } 38 39 @end
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