iOSSwift利用UICollectionView實(shí)現(xiàn)無(wú)限輪播功能（原理）詳解

collectionView.isPagingEnabled = true

 func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
 let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ImageCollectionViewCell", for: indexPath) as! ImageCollectionViewCell
 
 /// 給圖片賦值（在首尾分別添加兩張圖片）
 if (indexPath.row == 0) {
  cell.imageName = imageNameList.last
 } else if (indexPath.row == self.imageNameList.count + 1) {
  cell.imageName = imageNameList.first
 } else {
  cell.imageName = imageNameList[indexPath.row - 1]
 }
 
 return cell
 }

 func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
 /// 當(dāng)UIScrollView滑動(dòng)到第一位停止時(shí)，將UIScrollView的偏移位置改變
 if (scrollView.contentOffset.x == 0) {
  scrollView.contentOffset = CGPoint(x: CGFloat(self.imageNameList.count) * kScreenWidth,y: 0)
  self.pageControl.currentPage = self.imageNameList.count
  /// 當(dāng)UIScrollView滑動(dòng)到最后一位停止時(shí)，將UIScrollView的偏移位置改變
 } else if (scrollView.contentOffset.x == CGFloat(self.imageNameList.count + 1) * kScreenWidth) {
  scrollView.contentOffset = CGPoint(x: kScreenWidth,y: 0)
  self.pageControl.currentPage = 0
 } else {
  self.pageControl.currentPage = Int(scrollView.contentOffset.x / kScreenWidth) - 1
 }
 }

import UIKit

let kScreenWidth = UIScreen.main.bounds.width

class ViewController: UIViewController {
 
 lazy var collectionView: UICollectionView = {
 let flowLayout = UICollectionViewFlowLayout()
 flowLayout.minimumLineSpacing = 0
 flowLayout.minimumInteritemSpacing = 0
 flowLayout.scrollDirection = .horizontal
 flowLayout.itemSize = CGSize(width: kScreenWidth, height: 200)
 
 let collectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 200), collectionViewLayout: flowLayout)
 
 collectionView.isPagingEnabled = true
 collectionView.showsHorizontalScrollIndicator = false
 collectionView.backgroundColor = UIColor.white
 collectionView.delegate = self
 collectionView.dataSource = self
 self.view.addSubview(collectionView)
 
 return collectionView
 }()
 
 lazy var pageControl: UIPageControl = {
 let pageControl = UIPageControl(frame: CGRect(x: 0, y: 150, width: kScreenWidth, height: 50))
 
 pageControl.numberOfPages = self.imageNameList.count
 pageControl.currentPage = 0
 
 pageControl.tintColor = UIColor.black
 pageControl.pageIndicatorTintColor = UIColor.gray;
 
 return pageControl;
 }()
 
 lazy var imageNameList: [String] = {
 let imageList = ["image0", "image1", "image2", "image3"]
 
 return imageList
 }()

 override func viewDidLoad() {
 super.viewDidLoad()
 
 setupController()
 }
 
 func setupController() {
 /// 設(shè)置數(shù)據(jù)
 collectionView.register(ImageCollectionViewCell.self, forCellWithReuseIdentifier: "ImageCollectionViewCell")
 
 collectionView.reloadData()
 collectionView.scrollToItem(at: IndexPath(row: 1, section: 0), at: .left, animated: false)
 
 self.view.addSubview(pageControl)
 }

}

extension ViewController: UICollectionViewDataSource {
 
 func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
 /// 這步只是防止崩潰
 if (imageNameList.count == 0) {
  return 0
 }
 return imageNameList.count + 2
 }
 
 func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
 let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ImageCollectionViewCell", for: indexPath) as! ImageCollectionViewCell
 
 /// 給圖片賦值（在首尾分別添加兩張圖片）
 if (indexPath.row == 0) {
  cell.imageName = imageNameList.last
 } else if (indexPath.row == self.imageNameList.count + 1) {
  cell.imageName = imageNameList.first
 } else {
  cell.imageName = imageNameList[indexPath.row - 1]
 }
 
 return cell
 }
 
}

extension ViewController: UICollectionViewDelegate {
 
 func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
 /// 當(dāng)UIScrollView滑動(dòng)到第一位停止時(shí)，將UIScrollView的偏移位置改變
 if (scrollView.contentOffset.x == 0) {
  scrollView.contentOffset = CGPoint(x: CGFloat(self.imageNameList.count) * kScreenWidth,y: 0)
  self.pageControl.currentPage = self.imageNameList.count
  /// 當(dāng)UIScrollView滑動(dòng)到最后一位停止時(shí)，將UIScrollView的偏移位置改變
 } else if (scrollView.contentOffset.x == CGFloat(self.imageNameList.count + 1) * kScreenWidth) {
  scrollView.contentOffset = CGPoint(x: kScreenWidth,y: 0)
  self.pageControl.currentPage = 0
 } else {
  self.pageControl.currentPage = Int(scrollView.contentOffset.x / kScreenWidth) - 1
 }
 }
 
}

/// collectionView圖片的cell
class ImageCollectionViewCell: UICollectionViewCell {
 
 /// 顯示的圖片
 let imageView = UIImageView()
 var imageName: String? = "" {
 didSet {
  if let name = imageName {
  imageView.image = UIImage(named: name)
  }
 }
 }
 
 override init(frame: CGRect) {
 super.init(frame: frame)
 
 setupCell();
 }
 
 /// 初始化視圖
 func setupCell() {
 imageView.frame = self.bounds
 contentView.addSubview(imageView)
 }
 
 required init?(coder aDecoder: NSCoder) {
 fatalError("init(coder:) has not been implemented")
 } 
}