ios - 如何使用 ImageView 制作无限分页 ScrollView ？

Question

我有一个分页 UIScrollView，它每 5 秒自动向左滚动 4 个按顺序排列的 UIImage View 。当 ScrollView 到达第 4 个 ImageView 时，它会一直滚动回到第一个 ImageView 并重新开始。

创建无限 ScrollView 幻觉的最佳方法是什么？换句话说，我根本不想让 ScrollView 返回，而是让它继续向前滚动，当它到达第 4 个 ImageView 时，它向前滚动并且 ImageView #1 就在那里。

我想过重新添加 ImageView 并在 ScrollView 到达第 4 个图像时增加 ScrollView 的内容大小，但这不是很聪明...... idk

到目前为止，这是我的代码:

我的声明:

var pageImages = [UIImage]()
var pageViews: [UIImageView?] = []
var scrollTimer = NSTimer()
@IBOutlet weak var carousel: UIScrollView!

在 viewDidLoad() 中:

pageImages = [UIImage(named: "featured_1.png")!,
        UIImage(named: "featured_2.png")!,
        UIImage(named: "featured_3.png")!,
        UIImage(named: "featured_4.png")!]
    for _ in 0..<pageImages.count
       pageViews.append(nil)
}
var pagesScrollViewSize = carousel.frame.size

        carousel.contentSize = CGSize(width: pagesScrollViewSize.width * CGFloat(pageImages.count),
            height: pagesScrollViewSize.height)

loadVisiblePages()

以及定时器每5秒调用一次的函数:

func scrollToImage() {
        let x = carousel.contentOffset.x
        if (x <= (carousel.frame.width * CGFloat(pageImages.count))/2) {
        UIView.animateWithDuration(1, animations: {
            self.carousel.contentOffset = CGPointMake(x+self.carousel.frame.width, 0)
        })
        } else {
        UIView.animateWithDuration(1, animations: {
            self.carousel.contentOffset = CGPointMake(self.pageViews[0]!.frame.origin.x, 0)
        })
        }
    }

最后是完成大量工作的辅助函数:

func loadPage(page: Int) {
        if page < 0 || page >= pageImages.count {
            return
        }

        if let pageView = pageViews[page] {

        } else {
            var frame = carousel.bounds
            frame.origin.x = frame.size.width * CGFloat(page)
            frame.origin.y = 0.0

            let newPageView = UIImageView(image: pageImages[page])
            newPageView.contentMode = UIViewContentMode.ScaleToFill
            newPageView.frame = frame
            carousel.addSubview(newPageView)
            pageViews[page] = newPageView
        }
    }

    func loadVisiblePages() {
        let pageWidth = carousel.frame.size.width
        let page = Int(floor((carousel.contentOffset.x * 2.0 + pageWidth) / (pageWidth * 2.0)))

        let firstPage = page
        let lastPage = page + 3

        for index in firstPage...lastPage {
            loadPage(index)
        }
    }

Answer 1

想法是:

当图像在左侧超出框架时，将其移除并重新附加到最右侧图像的右侧。那时你重置内容偏移量

import UIKit

class ViewController: UIViewController {

    var pageViews: [UIImageView] = []
    var scrollTimer = NSTimer()

    @IBOutlet weak var carousel: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        pageViews = [
            UIImageView(image:UIImage(named: "featured_1.png")!),
            UIImageView(image:UIImage(named: "featured_2.png")!),
            UIImageView(image:UIImage(named: "featured_3.png")!),
            UIImageView(image:UIImage(named: "featured_4.png")!)
        ]
        var pagesScrollViewSize = carousel.frame.size
        carousel.contentSize = CGSize(width: pagesScrollViewSize.width * CGFloat(pageViews.count),height: pagesScrollViewSize.height)
        println(carousel.contentSize)

        scrollTimer = NSTimer.scheduledTimerWithTimeInterval(2.0, target: self, selector: "moveLeft", userInfo: nil, repeats: true)
    }

    override func viewDidAppear(animated: Bool) {
        showPage()
    }

    func showPage(){
        carousel.setContentOffset(CGPointZero, animated: false)
        for (index, page) in enumerate(pageViews) {
            var frame = page.frame
            frame.origin.x = carousel.frame.size.width * CGFloat(index)
            frame.origin.y = 0.0
            println(frame)
            page.contentMode = UIViewContentMode.ScaleToFill
            page.frame = frame
            carousel.addSubview(page)
        }

    }

    func moveLeft(){
        UIView.animateWithDuration(
            1.0,
            animations: {
                let x = self.carousel.contentOffset.x
                self.carousel.contentOffset = CGPointMake(x + self.carousel.frame.width, 0)
                println(self.carousel.contentOffset)
            }, completion: {complete in
                self.moveLeftEnd()
            }
        );
    }

    func moveLeftEnd(){
        let first = pageViews.removeAtIndex(0)
        pageViews.append(first)
        showPage()
    }
}