IOS開發之UIScrollView實現圖片輪播器的無限滾動
簡介
在現在的一些App中常常見到圖片輪播器，一般用于展示廣告、新聞等數據，在iOS內并沒有現成的控件直接實現這種功能，但是通過UIScrollView的允許分頁設置，可以實現滾動輪播的功能。
輪播原理
UIScrollView對象有pagingEnable成員，如果設置為YES，那么每一個scrollView尺寸這么大的區域就會被當作一頁，在滾動時會根據滾動的比例自動計算應該切換到哪一頁。
無限滾動原理
要實現無限滾動，需要額外的兩張圖片，假設我們的圖片有五張，存在images數組中，那么我們在將圖片插入到scrollView中時，在第一張圖片前面插入一個最后一張圖片作為輔助圖片，在最后一張后面插入一個第一張圖片作為輔助圖片。這樣，當滾動到第一張前面一張時，在頁面切換結束后無動畫的切換scrollView的偏移量為最后一張圖片（不包含最后一張后面的第一張那個輔助圖片），這樣就實現了由輔助圖片到真實圖片的過渡，之所以設置輔助圖片是為了在滾動中看到那個真實圖片。同理，當滾動到最后一張的后面一張時，我們吧scrollView的偏移量設置為第一張圖片即可。
具體的代碼實現
這個代碼是在開發一個項目中所寫的，已經封裝稱一個View，只需要調用initWithFrame指定輪播器尺寸，然后通過設置images成員的值即可實現無限滾動的輪播。
// .h//// ESPicPageView.h// 享技//// Created by 11 on 11/30/15.// Copyright © 2015 soulghost. All rights reserved.//#import <UIKit/UIKit.h>@interface ESPicPageView : UIView@property (nonatomic, strong) NSArray *images;@end// --------------------------------------------// .m//// ESPicPageView.m// 享技//// Created by 11 on 11/30/15.// Copyright © 2015 soulghost. All rights reserved.//#import "ESPicPageView.h"#import "UIImageView+WebCache.h"@interface ESPicPageView () <UIScrollViewDelegate>@property (nonatomic, weak) UIScrollView *scrollView;@property (nonatomic, weak) UIPageControl *pageControl;@property (nonatomic, assign) CGFloat imgW;@property (nonatomic, assign) CGFloat imgH;@property (nonatomic, strong) NSTimer *timer;@property (nonatomic, strong) NSArray *imageViews;@property (nonatomic, assign) NSInteger imageCount;@end@implementation ESPicPageView- (instancetype)initWithFrame:(CGRect)frame{ if (self = [super initWithFrame:frame]) { self.backgroundColor = [UIColor blueColor]; UIScrollView *scrollView = [[UIScrollView alloc] init]; self.scrollView = scrollView; self.scrollView.delegate = self; self.scrollView.pagingEnabled = YES; self.scrollView.showsHorizontalScrollIndicator = NO; self.scrollView.backgroundColor = [UIColor whiteColor]; [self addSubview:scrollView]; self.imgW = frame.size.width; self.imgH = frame.size.height; [self setNeedsLayout]; UIPageControl *pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(frame.size.width - 50, frame.size.height - 10, 0, 0)]; self.pageControl = pageControl; self.pageControl.numberOfPages = 1; [self addSubview:pageControl]; self.timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextImage) userInfo:nil repeats:YES]; [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes]; } return self;}- (void)nextImage{ NSInteger page = self.pageControl.currentPage; page = self.pageControl.currentPage + 1; CGPoint offset = CGPointMake((1 + page) * self.imgW, 0); [self.scrollView setContentOffset:offset animated:YES];}- (void)setupImageViews{ for (int i = 0; i < self.images.count + 2; i++) { UIImageView *imageView = [[UIImageView alloc] init]; CGFloat imageX = i * self.imgW; CGFloat imageY = 0; CGFloat imageW = self.imgW; CGFloat imageH = self.imgH; imageView.frame = CGRectMake(imageX, imageY, imageW,imageH); [self.scrollView insertSubview:imageView atIndex:0]; }}- (NSArray *)imageViews{ if (_imageViews == nil) { NSMutableArray *arr = [NSMutableArray array]; for (int i = 0; i < self.images.count + 2; i++) { UIImageView *imageView = [[UIImageView alloc] init]; CGFloat imageX = i * self.imgW; CGFloat imageY = 0; CGFloat imageW = self.imgW; CGFloat imageH = self.imgH; imageView.frame = CGRectMake(imageX, imageY, imageW,imageH); [self.scrollView insertSubview:imageView atIndex:0]; [arr addObject:imageView]; } _imageViews = arr; } return _imageViews;}- (void)setImages:(NSArray *)images{ _images = images; self.imageCount = images.count; self.pageControl.numberOfPages = self.imageCount; [self addPics];}- (void)addPics{ for (int i = 0; i < self.images.count + 2; i++) { UIImageView *imageView = self.imageViews[i]; if (i == 0) { imageView.image = [self.images lastObject]; }else if(i == self.images.count + 1){ imageView.image = [self.images firstObject]; }else{ imageView.image = self.images[i - 1]; } }}- (void)layoutSubviews{ [super layoutSubviews]; self.scrollView.frame = self.bounds; self.scrollView.contentSize = CGSizeMake((self.imageCount + 2) * self.imgW, 0); [self.scrollView setContentOffset:CGPointMake(self.imgW, 0) animated:NO];}- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{ [self.timer invalidate]; self.timer = nil;}- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{ self.timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextImage) userInfo:nil repeats:YES]; [[NSRunLoop currentRunLoop ] addTimer:self.timer forMode:NSRunLoopCommonModes];}- (void)scrollViewDidScroll:(UIScrollView *)scrollView{ if (scrollView.contentOffset.x == self.imgW * (self.imageCount + 1)) { [self.scrollView setContentOffset:CGPointMake(self.imgW, 0) animated:NO]; }else if(scrollView.contentOffset.x == 0){ [self.scrollView setContentOffset:CGPointMake(self.imgW * (self.imageCount), 0) animated:NO]; } self.pageControl.currentPage = (self.scrollView.contentOffset.x + self.imgW * 0.5f) / self.imgW - 1;}@end以上就是使用UIScrollView實現圖片的輪播的功能，如有疑問大家可以留言，也可以到本站社區留言討論，感謝閱讀，希望能幫助到大家，謝謝大家對本站的支持！
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