效果图如下：

CustomCollectionViewLayout.gif

实现思路：

利用n+2个元素实现

实现步骤：

1.自定义View，添加scrollView，pageControl和timer

class ImageCircleView: UIView {

var imagesArr:[String]? {
    didSet {
        setupImageViews()
    }
}
var newImagesArr:[String] = [String]()
var timer: Timer!
var scrollView: UIScrollView!
var pageControl: UIPageControl!
var imageWidth: CGFloat = 0
var imageCount: Int = 0
var currentIndex: Int = 0
var duration: TimeInterval = 3.0
var pageColor: UIColor = UIColor.white
var currentPageColor: UIColor = UIColor.black

override init(frame: CGRect) {
    super.init(frame: frame)
    setupUI()
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

func setupUI() -> Void {
    setupScrollView()
    setupPageControl()
    setupTimer()
}

func setupScrollView() -> Void {

    scrollView = UIScrollView(frame: self.bounds)
    scrollView.delegate = self
    scrollView.isPagingEnabled = true
    scrollView.showsHorizontalScrollIndicator = false
    scrollView.showsVerticalScrollIndicator = false
    addSubview(scrollView)
}

func setupPageControl() -> Void {
    pageControl = UIPageControl(frame: CGRect(x: (self.frame.width - 200) * 0.5, y: self.frame.size.height * 0.8, width: 200, height: 20))
    pageControl.currentPageIndicatorTintColor = currentPageColor
    pageControl.pageIndicatorTintColor = pageColor
    addSubview(pageControl)
}

func setupImageViews() -> Void {
    guard let images = imagesArr else {
        return
    }
    guard let first = images.first, let last = images.last else {
        return
    }
    newImagesArr.removeAll()
    _ = scrollView.subviews.map { (view) -> Void in
        view.removeFromSuperview()
    }
    
    if images.count == 1 {
        removeTimer()
        newImagesArr += images
    }else {
        newImagesArr.append(last)
        newImagesArr += images
        newImagesArr.append(first)
    }
    
    imageCount = images.count
    pageControl.numberOfPages = imageCount
    
    let imageW:CGFloat = self.frame.size.width
    let imageH:CGFloat = self.frame.size.height
    var imageX:CGFloat = 0
    let imageY:CGFloat = 0
    imageWidth = imageW
    scrollView.contentSize = CGSize(width: CGFloat(newImagesArr.count) * imageWidth, height: imageH)
    scrollView.setContentOffset(imageCount > 1 ? CGPoint(x: imageWidth, y: 0) : CGPoint.zero, animated: true)
    currentIndex = 0

    for i in 0..<newImagesArr.count {
        imageX = imageW * CGFloat(i)
        let imageView = UIImageView(frame: CGRect(x: imageX, y: imageY, width: imageW, height: imageH))
        imageView.image = UIImage(named: newImagesArr[i])
        scrollView.addSubview(imageView)
    }
}

//Mark: - Timer
func setupTimer() -> Void {
    timer = Timer(timeInterval: duration, target: self, selector: #selector(nextPage), userInfo: nil, repeats: true)
    RunLoop.main.add(timer, forMode: RunLoopMode.commonModes)
}

func nextPage() -> Void {

    pauseTimer()
//        currentIndex += 1
    var offset = scrollView.contentOffset
    offset.x += imageWidth
    scrollView.setContentOffset(offset, animated: true)
}

func removeTimer() -> Void {
    if timer != nil {
        timer.invalidate()
        timer = nil
    }
}

func pauseTimer() -> Void {
    if timer.isValid {
        timer.fireDate = Date.distantFuture
    }
}

func openTimer() -> Void {
    if timer.isValid {
        timer.fireDate = Date(timeIntervalSinceNow: duration)
    }
}
deinit {
    removeTimer()
}

}

2.在控制器中的代理方法

extension ImageCircleView: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
    
    currentIndex = Int(self.scrollView.contentOffset.x / imageWidth) - 1

    if self.scrollView.contentOffset.x <= 0 {
        
        currentIndex = imageCount - 1
        self.scrollView.setContentOffset(CGPoint(x: CGFloat(imageCount) * imageWidth, y: 0), animated: false)
    }
    if self.scrollView.contentOffset.x >= CGFloat(imageCount + 1) * imageWidth {
        
        currentIndex = 0
        self.scrollView.setContentOffset(CGPoint(x: imageWidth, y: 0), animated: false)
    }
    
    pageControl.currentPage = currentIndex
}

func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
    openTimer()
}

func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
    pauseTimer()
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    openTimer()
}
}

3.在控制器中使用：

import UIKit
class ImageCircleViewController: UIViewController {

var imageCircleView:ImageCircleView = ImageCircleView(frame:CGRect(x: 0, y: 30, width: UIScreen.main.bounds.size.width, height: 260))

override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = UIColor.white
    setupUI()
}

func setupUI() -> Void {
    
    imageCircleView.imagesArr = ["01","02","03","04","05","06"]
    imageCircleView.backgroundColor = UIColor.lightGray
    view.addSubview(imageCircleView)
}
}