UIScrollView轮播图

一、想法思路

首先scrollview的contentSize为3个屏幕的宽度，3个UIImageView一次排列在scrollview上，默认scrollview.contentOffset.x为一个屏幕宽度，每滚动一次，更新3个imageView的图片，更新完图片再调用scrollRectToVisible: animated:方法使scrollview的contentOffset.x滚回到一个屏幕的宽度，第二个imageView永远保持在中间的位置，只是图片换了，每次滑动后持续上述的操作，这样就能不停轮播切换图片的效果，当然这只是一种思路，你用其他办法能实现这个效果也可以。

说明：此处并无针对实际项目作出相关处理，只提供思路，实际情况请根据项目情况自行处理。

二、代码

我们先来看.h

#import <UIKit/UIKit.h>

@class TestBannerView;

@interface TestBannerView : UIView

@property (nonatomic, strong) NSArray *sources;

@property (nonatomic, assign) float scrollTime;

@end

然后是.m文件

#define BannerWidth self.bounds.size.width
#define BannerHight self.bounds.size.height

#import "TestBannerView.h"

@interface TestBannerView ()< UIScrollViewDelegate >

@property (nonatomic, strong) UIScrollView *scrollView;

@property (nonatomic, strong) UIPageControl *pageControl;

@property (nonatomic, strong) NSTimer *scrollTimer;

@property (nonatomic, assign) int currentPage;

@property (nonatomic, strong) UIImageView *previousImageView;

@property (nonatomic, strong) UIImageView *currentImageView;

@property (nonatomic, strong) UIImageView *nextImageView;

@end

- (void)setFrame:(CGRect)frame
{
    [super setFrame:frame];
    [self initSubView];
}
- (void)initSubView
{
    [self addSubview:self.scrollView];
    [self addSubview:self.pageControl];
    [_scrollView addSubview:self.previousImageView];
    [_scrollView addSubview:self.currentImageView];
    [_scrollView addSubview:self.nextImageView];
}

- (void)setSources:(NSArray *)sources
{
    _sources = [sources copy];
    if (_sources.count <= 1)
    {
        _pageControl.hidden = YES;
        _scrollView.contentSize = CGSizeMake(BannerWidth, BannerHight);
        
    }else{
        _pageControl.hidden = NO;
        _pageControl.numberOfPages = _sources.count;
        _scrollView.contentSize = CGSizeMake(BannerWidth * 3, BannerHight);
    }
    [self updateImage];
}
- (void)updateImage
{
    if (_currentPage >= (int)_sources.count) _currentPage = 0;
    
    if (_currentPage < 0) {
        _currentPage = (int)_sources.count-1;
    }
    
    int previous = (_currentPage - 1) < 0 ? (int)_sources.count - 1 : _currentPage - 1;
    
    int next = (_currentPage + 1) >= (int)_sources.count ? 0 : _currentPage + 1;

    if (_sources.count > 0) {
        _pageControl.currentPage = _currentPage;
        NSString *preStr = [_sources objectAtIndex:previous] ;
        NSString *currentStr = [_sources objectAtIndex:_currentPage];
        NSString *nextStr = [_sources objectAtIndex:next];

        _previousImageView.image = [UIImage imageNamed:preStr];
        _currentImageView.image = [UIImage imageNamed:currentStr];
        _nextImageView.image = [UIImage imageNamed:nextStr];
    

    }
    [_scrollView scrollRectToVisible:CGRectMake(BannerWidth, 0, BannerWidth, BannerHight) animated:NO];
    _scrollTime = _scrollTime > 0 ? _scrollTime : 1.5;
    [self startTimer];
}
- (void)startTimer
{
    if (_scrollTimer) {
        [_scrollTimer invalidate];
        _scrollTimer = nil;
    }
    _scrollTimer = [NSTimer timerWithTimeInterval:_scrollTime target:self selector:@selector(imageScroll:) userInfo:nil repeats:NO];
    
    [[NSRunLoop currentRunLoop] addTimer:_scrollTimer forMode:NSDefaultRunLoopMode];
}

- (void)imageScroll:(NSTimer *)timer
{
    if (!_scrollView.isDragging) {
        [_scrollView scrollRectToVisible:CGRectMake(2*BannerWidth, 0, BannerWidth, BannerHight) animated:YES];
        _currentPage++;
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [self updateImage];
        });
    }
}

// UIScrollViewDelegate
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    if (_scrollTimer) {
        [_scrollTimer invalidate];
        _scrollTimer = nil;
    }
    
    if (scrollView.contentOffset.x>=BannerWidth*2)
        _currentPage++;
    else if (scrollView.contentOffset.x<BannerWidth)
        _currentPage--;
    
    [self updateImage];
}

// Set/Get
- (UIScrollView *)scrollView
{
    if (!_scrollView) {
        _scrollView = [[UIScrollView alloc] initWithFrame:self.bounds];
        _scrollView.pagingEnabled = YES;
        _scrollView.showsHorizontalScrollIndicator = NO;
        _scrollView.bounces = NO;
        _scrollView.delegate = self;
    }
    return _scrollView;
}

- (UIPageControl *)pageControl
{
    if (!_pageControl) {
        _pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, BannerHight-50, BannerWidth, 50)];
        _pageControl.currentPageIndicatorTintColor = [UIColor redColor];
        _pageControl.enabled = NO;
        _pageControl.pageIndicatorTintColor = [UIColor blueColor];
    }
    return _pageControl;
}

- (UIImageView *)previousImageView
{
    if (!_previousImageView) {
        _previousImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, BannerWidth, BannerHight)];
    }
    return _previousImageView;
}

- (UIImageView *)currentImageView
{
    if (!_currentImageView) {
        _currentImageView = [[UIImageView alloc]initWithFrame:CGRectMake(BannerWidth, 0, BannerWidth, BannerHight)];
    }
    return _currentImageView;
}

- (UIImageView *)nextImageView
{
    if (!_nextImageView) {
        _nextImageView = [[UIImageView alloc]initWithFrame:CGRectMake(BannerWidth * 2, 0, BannerWidth, BannerHight)];
    }
    return _nextImageView;
}

// 调用
TestBannerView *banner = [[TestBannerView alloc]initWithFrame:CGRectMake(0, 64, WIDTH, 100)];
banner.backgroundColor = [UIColor yellowColor];
banner.sources = @[@"face1",@"face2",@"face3",@"face4"];
[self.view addSubview:banner];

结语： 开始养成好习惯，不间断更新文章，为自己，加油！！！

有什么问题或者建议或者更好的思路，欢迎留言探讨，谢谢！！！