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IOS開發(fā)之UIScrollView實現(xiàn)圖片輪播器的無限滾動

2020-01-26 14:01:19
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IOS開發(fā)之UIScrollView實現(xiàn)圖片輪播器的無限滾動

簡介

在現(xiàn)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(shù)據(jù),在iOS內(nèi)并沒有現(xiàn)成的控件直接實現(xiàn)這種功能,但是通過UIScrollView的允許分頁設(shè)置,可以實現(xiàn)滾動輪播的功能。

輪播原理

UIScrollView對象有pagingEnable成員,如果設(shè)置為YES,那么每一個scrollView尺寸這么大的區(qū)域就會被當(dāng)作一頁,在滾動時會根據(jù)滾動的比例自動計算應(yīng)該切換到哪一頁。

無限滾動原理

要實現(xiàn)無限滾動,需要額外的兩張圖片,假設(shè)我們的圖片有五張,存在images數(shù)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(dāng)滾動到第一張前面一張時,在頁面切換結(jié)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(xiàn)了由輔助圖片到真實圖片的過渡,之所以設(shè)置輔助圖片是為了在滾動中看到那個真實圖片。同理,當(dāng)滾動到最后一張的后面一張時,我們吧scrollView的偏移量設(shè)置為第一張圖片即可。

具體的代碼實現(xiàn)

這個代碼是在開發(fā)一個項目中所寫的,已經(jīng)封裝稱一個View,只需要調(diào)用initWithFrame指定輪播器尺寸,然后通過設(shè)置images成員的值即可實現(xiàn)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(xiàn)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(qū)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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