Banner

需求如下：
（1）无限循环轮播
（2）定时轮播
（3）添加PageControl

import UIKit

class HomePageBannerView: UIView {
    
    //MARK: - 属性 & 事件
    @IBOutlet weak var collectionView: UICollectionView!
    @IBOutlet weak var pageControl: UIPageControl!
    let ItemCountTimes = Int(100)//item数的倍数
    let bannerViewHeight = kScreenWidth*(116.0/375.0)
    lazy var layout: UICollectionViewFlowLayout = {
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 0
        layout.minimumInteritemSpacing = 0
        layout.sectionInset = UIEdgeInsets.init(top: 0, left: 0, bottom: 0, right: 0)
        layout.scrollDirection = .horizontal
        layout.itemSize = CGSize.init(width: kScreenWidth, height: bannerViewHeight)
        return layout
    }()
    var dataSource: [AdvListModel]? {
        didSet {
            guard dataSource != nil  else {
                return
            }
            collectionView.reloadData()
            collectionView.scrollToItem(at: IndexPath.init(row: dataSource!.count*(ItemCountTimes/2), section: 0), at: UICollectionViewScrollPosition.left, animated: false)
            pageControl.numberOfPages = dataSource?.count ?? 0
            pageControl.currentPage = 0
            
            self.addTimer1()
        }
    }
    var timer:Timer?
    
    
    //MARK: - 生命周期
    override func awakeFromNib() {
        super.awakeFromNib()
        
        self.prepareUI()
    }
    
    deinit {
        self.removeTimer()
    }
    
    
    //MARK: - UI设置
    func prepareUI() {
        collectionView.isPagingEnabled = true
        collectionView.showsHorizontalScrollIndicator = false
        collectionView.showsVerticalScrollIndicator = false
        collectionView.delegate = self
        collectionView.dataSource = self
        let nib = UINib(nibName: "HomePageBannerCell", bundle: nil)
        collectionView.register(nib, forCellWithReuseIdentifier: "HomePageBannerCell")
        collectionView.setCollectionViewLayout(layout, animated: true)
        
        pageControl.hidesForSinglePage = true
    }

}


// MARK: - UICollectionViewDelegate,UICollectionViewDataSource
extension HomePageBannerView: UICollectionViewDelegate,UICollectionViewDataSource {
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return (dataSource?.count ?? 0)*ItemCountTimes
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "HomePageBannerCell", for: indexPath) as! HomePageBannerCell
        let model = dataSource![indexPath.item%dataSource!.count]
        cell.model = model
        return cell
    }
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    }
    
}


// MARK: - UIScrollViewDelegate
extension HomePageBannerView: UIScrollViewDelegate {
    
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        //页书为0 不需要设置page
        guard (self.dataSource?.count ?? 0) > 0 else {
            return
        }
        let page = Int((scrollView.contentOffset.x/scrollView.frame.size.width+0.5))%self.dataSource!.count
        self.pageControl.currentPage = page
    }
    
    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        self.removeTimer()
    }
    
    func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        self.addTimer1()
    }
    
}


// MARK: - 定时器相关
extension HomePageBannerView {
    
    //添加timer
    func addTimer1() {
        self.timer = Timer.scheduledTimer(timeInterval: 3.0, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
    }
    
    //销毁timer
    func removeTimer() {
        self.timer?.invalidate()
        self.timer = nil
    }
    
    
    //selector方法
    @objc func timerAction() {
        guard (self.dataSource?.count ?? 0) > 0 else {
            return
        }
        //获取当前正在展示的位置
        let currentIndexPath = self.collectionView.indexPathsForVisibleItems.last
        //回到中间相应的显示位置
        let currentIndexPathRest = IndexPath.init(item: (dataSource!.count*(ItemCountTimes/2))+(currentIndexPath!.item%dataSource!.count), section: 0)
        self.collectionView.scrollToItem(at: currentIndexPathRest, at: .left, animated: false)
        //通过动画滚动到下一个位置
        let nextItem = currentIndexPathRest.item+1
        let nextIndexPath = IndexPath.init(item: nextItem, section: 0)
        self.collectionView.scrollToItem(at: nextIndexPath, at: .left, animated: true)//回到中间相应的显示位置
    }
    
}