时间戳

首页 > 解决方案 > 如何在 Xcode 项目的 Scroll View 上无限滚动？

ios - 如何在 Xcode 项目的 Scroll View 上无限滚动？

问题描述

我的应用程序中有一个 Scrollview 显示几张幻灯片，幻灯片的默认行为是当您到达最后一张（例如幻灯片 5）时，它不会向右滚动更多，或者当您转到第一个它不会向左滚动更多。

我如何使它无限循环，这意味着当我看到最后一张幻灯片时，我向右滚动，它只会滚动到第一张？（或从第一个左侧滚动到最后一个）

这是我的scrollViewDidScroll：

func scrollViewDidScroll(_ scrollView: UIScrollView) {
        let pageIndex = round(scrollView.contentOffset.x/view.frame.width)
        pageControl.currentPage = Int(pageIndex)

        let maximumHorizontalOffset: CGFloat = scrollView.contentSize.width - scrollView.frame.width
        let currentHorizontalOffset: CGFloat = scrollView.contentOffset.x

        // vertical
        let maximumVerticalOffset: CGFloat = scrollView.contentSize.height - scrollView.frame.height
        let currentVerticalOffset: CGFloat = scrollView.contentOffset.y

        let percentageHorizontalOffset: CGFloat = currentHorizontalOffset / maximumHorizontalOffset
        let percentageVerticalOffset: CGFloat = currentVerticalOffset / maximumVerticalOffset


        /*
         * below code changes the background color of view on paging the scrollview
         */
        //        self.scrollView(scrollView, didScrollToPercentageOffset: percentageHorizontalOffset)


        /*
         * below code scales the imageview on paging the scrollview
         */
        let percentOffset: CGPoint = CGPoint(x: percentageHorizontalOffset, y: percentageVerticalOffset)
        print ("present offset: ", percentOffset.x)
        if(percentOffset.x > 0 && percentOffset.x <= 0.25) {

            slides[0].mainPic.transform = CGAffineTransform(scaleX: (0.25-percentOffset.x)/0.25, y: (0.25-percentOffset.x)/0.25)
            slides[1].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x/0.25, y: percentOffset.x/0.25)

        } else if(percentOffset.x > 0.25 && percentOffset.x <= 0.50) {
            slides[1].mainPic.transform = CGAffineTransform(scaleX: (0.50-percentOffset.x)/0.25, y: (0.50-percentOffset.x)/0.25)
            slides[2].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x/0.50, y: percentOffset.x/0.50)

        } else if(percentOffset.x > 0.50 && percentOffset.x <= 0.75) {
            slides[2].mainPic.transform = CGAffineTransform(scaleX: (0.75-percentOffset.x)/0.25, y: (0.75-percentOffset.x)/0.25)
            slides[3].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x/0.75, y: percentOffset.x/0.75)

        } else if(percentOffset.x > 0.75 && percentOffset.x <= 1) {
            slides[3].mainPic.transform = CGAffineTransform(scaleX: (1-percentOffset.x)/0.25, y: (1-percentOffset.x)/0.25)
            slides[4].mainPic.transform = CGAffineTransform(scaleX: percentOffset.x, y: percentOffset.x)

        } 
    }

标签： iosxcode

解决方案

不确定您当前的实现，但您的解决方案将类似于，我假设您的slides数组包含每张幻灯片的 UIView。根据您当前的实现更改代码。

(void)scrollViewDidScroll:(UIScrollView *)scrollView {

    if(if(scrollView.contentOffset.x < 0)) {
        CGPoint newOffset = CGPointMake(scrollView.bounds.size.width+scrollView.contentOffset.x, scrollView.contentOffset.y);
        [scrollView setContentOffset:newOffset];
        [self rotateViewsRight];
    }
    else if(scrollView.contentOffset.x > scrollView.bounds.size.width*2) {
        CGPoint newOffset = CGPointMake(scrollView.contentOffset.x-scrollView.bounds.size.width, scrollView.contentOffset.y);
        [scrollView setContentOffset:newOffset];
        [self rotateViewsLeft];
    }
}

-(void)rotateViewsRight {
    UIView *endView = [slides lastObject];
    [slides removeLastObject];
    [slides insertObject:endView atIndex:0];
    [self setContentViewFrames];

}

-(void)rotateViewsLeft {
    UIView *endView = slides[0];
    [slides removeObjectAtIndex:0];
    [slides addObject:endView];
    [self setContentViewFrames];

}

-(void) setContentViewFrames {
    for(int i = 0; i < 5; i++) {
        UIView * view = slides[i];
        [view setFrame:CGRectMake(self.view.bounds.size.width*i, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
    }
}

推荐阅读