UIScrollView无缝滚动_uiscrollview无缝翻页原理-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_27561705/article/details/49993723

本文介绍了在iOS开发中实现UIScrollView无缝滚动的需求，通过创建额外的视图并调整偏移量来模拟无缝效果。作者在实践中遇到问题，并参考网络资料进行优化，最终整理出清晰的实现方案。

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工程里遇到了无缝滚动的需求，自己尝试着写了下，原理基本就是通过多建2个imageView，一个放在最前，一个放在最后，然后通过偏移量判断，[scrollView setContentOffset: animated:NO]; 或者 [scrollView scrollRectToVisible: animated:NO];再通过此方法改变位置实现，最后发现怎么都不能真正的无缝。
上网查了资料，原理虽然跟我原理一样，但处理的比我好很多，不过整理的太乱，于是想整理清楚分享给大家，本无颜称为原创，但毕竟自己原理无错，也是自己整理的，就脸厚了一下。

宏

#define WIDTH 375   //页面宽
#define HEIGHT 400   //页面高

创建ScrollView

@interface ViewController ()
{
    NSMutableArray *imageArray;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    self.scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 100, WIDTH, HEIGHT)];
    self.scrollView.bounces = YES;  //是否允许弹性滑动
    self.scrollView.pagingEnabled = YES;   //设置是否分页
    self.scrollView.delegate = self;    //代理
    self.scrollView.userInteractionEnabled = YES;  //交互性

    imageArray = [[NSMutableArray alloc] init];
    [imageArray addObject:@"image1"];
    [imageArray addObject:@"image2"];
    [imageArray addObject:@"image3"];
    [imageArray addObject:@"image4"];
    [imageArray addObject:@"image5"];

    //添加最后一张图片到第一个位置
    UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[imageArray objectAtIndex:([imageArray count]-1)]]];
    imageView.frame = CGRectMake(0, 0, WIDTH, HEIGHT);
    [self.scrollView addSubview:imageView];

    for (int i = 0;i<[imageArray count];i++) {
        //loop this bit
        UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[imageArray objectAtIndex:i]]];
        imageView.frame = CGRectMake((WIDTH * i) + 320, 0, WIDTH, HEIGHT);
        [self.scrollView addSubview:imageView];

        //
    }

    //添加第一张图片到第最后一个位置
    imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:[imageArray objectAtIndex:0]]];
    imageView.frame = CGRectMake((WIDTH * ([imageArray count] + 1)), 0, WIDTH, HEIGHT);
    [self.scrollView addSubview:imageView];


    [self.scrollView setContentSize:CGSizeMake(WIDTH * ([imageArray count] + 2), HEIGHT)];
    [self.scrollView setContentOffset:CGPointMake(0, 0)];
    [self.view addSubview:self.scrollView];
    [self.scrollView scrollRectToVisible:CGRectMake(WIDTH,0,WIDTH,HEIGHT) animated:NO];

}

最后也是关键的一步了，在协议方法里面判断

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
      CGPoint point=scrollView.contentOffset;
     if ((int)point.x==0) {
        [self.scrollView scrollRectToVisible:CGRectMake(WIDTH * [imageArray count],0,WIDTH,HEIGHT) animated:NO];
    } else if ((int)point.x==([imageArray count]+1)*WIDTH) {
        [self.scrollView scrollRectToVisible:CGRectMake(WIDTH,0,WIDTH,HEIGHT) animated:NO];
    }
}