Swift - UIScrollView 循环滚动（2）

大家好，这篇文章和UIScrollView 循环滚动 1功能是相通的，但是实现的理念是完全不同的，更适合网络懒加载图片。

【实现原理】

1、当imageCount == 1时

• 在scrollView中建立一个UIImageView，不显示pageController，同时不支持滚动

2、当imageCount > 1时

• 在scrollView中建立imageCount + 1 个 UIImageView，显示pageController，pageController 的 page = imageCount
• 最后一个UIImageView赋值为第一个的值
• 当滚动到最后一张时，将scrollView的contentOff调到第一张图的位置（0， 0）

【代码】

实现语言swift

import UIKit

class JDFilmstripView: JDView {
    var imageArr: Array<UIImage> = []  {
        didSet {//赋值刷线UI控件  值为UIImage对象
            self.reloadView()
        }
    }
    var imageUrlArr: Array<JDImgUrlTitleModel> = [] {
        didSet {//赋值刷线UI控件  值为Url对象
             self.reloadView()
        }
    }
    
    //是否自动跳转
    var autoShow: Bool = false 
    //当前页面记录
    var currentPage: Int = 0
    //轮播控制时间计时器
    lazy var autoTimer: Timer? = {
        let timer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
        return timer
    }()

    //MARK: - 控件 
    lazy var imageVArr: Array<UIImageView> = {
        var arr: Array<UIImageView> = []
        return arr
    }()
    lazy var scrollview: UIScrollView = {
        let v = UIScrollView()
        v.showsVerticalScrollIndicator = false
        v.showsHorizontalScrollIndicator = false
        v.isPagingEnabled = true
        v.bounces = false
        v.delegate = self
        return v
    }()
    lazy var pageControl: UIPageControl = {
        let pc = UIPageControl()
        pc.isUserInteractionEnabled = false
        pc.pageIndicatorTintColor = UIColor(red: 255/255, green: 255/255, blue: 255/255, alpha: 0.3)
        pc.currentPageIndicatorTintColor = color_nav_red
        return pc
    }()

    override init() {
        super.init()
        self.addSubview(self.scrollview)
        self.addSubview(self.pageControl)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        self.scrollview.snp.makeConstraints { (make) in
            make.top.right.bottom.left.equalToSuperview()
        }
        self.pageControl.snp.makeConstraints { (make) in
            make.bottom.left.right.equalToSuperview()
            make.height.equalTo(20.0)
        }
    }
    
    deinit {
        self.autoTimer?.invalidate()
        self.autoTimer = nil
    }
    
    /*
    // Only override draw() if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func draw(_ rect: CGRect) {
        // Drawing code
    }
    */

}

extension JDFilmstripView {
    func reloadView() {
        for imagev in self.imageVArr {
            imagev.removeFromSuperview()
        }
        self.imageVArr.removeAll()
        
        var count: Int = 0
        if self.imageUrlArr.count > 0 {
            count = self.imageUrlArr.count
        }
        else if self.imageArr.count > 0 {
            count = self.imageArr.count
        }
        
        let w = screen_width
        let h = 160
        self.scrollview.contentSize = CGSize(width: w * CGFloat(count), height: CGFloat(h))
        
        var term = count
        if term > 0  {
            term = count + 1
        }
        for i in 0..<term {
            let imageV = UIImageView.init()
            imageV.backgroundColor = UIColor.red
            imageV.frame = CGRect(x: CGFloat(i) * w, y: 0, width: w, height: CGFloat(h))
            
            if self.imageUrlArr.count > 0 {
                if i == term - 1 {
                    imageV.sd_setImage(with: URL(string:self.imageUrlArr[0].img) , placeholderImage: UIImage(named: "banner"))
                }
                else {
                    imageV.sd_setImage(with: URL(string:self.imageUrlArr[i].img) , placeholderImage: UIImage(named: "banner"))
                }
            }
            else if self.imageArr.count > 0 {
                if i == term - 1 {
                    imageV.image = self.imageArr[0]
                }
                else {
                    imageV.image = self.imageArr[i]
                }
            }
            self.imageVArr.append(imageV)
            self.scrollview.addSubview(imageV)
        }
        
        self.currentPage = 0
        self.pageControl.numberOfPages = count
        self.pageControl.currentPage = 0
        if count > 1 {
            self.pageControl.isHidden = false
            self.scrollview.isScrollEnabled = true
        }
        else {
            self.pageControl.isHidden = true
            self.scrollview.isScrollEnabled = false
        }
        
        if self.autoShow && count > 1{
            self.startTimer()
        } else {
            self.stopTimer()
        }
    }
    
    @objc func startTimer() {
        if self.autoShow {
            self.autoTimer?.fireDate = Date.distantPast
        }
    }
    
    func stopTimer() {
        if self.autoShow {
            self.autoTimer?.fireDate = Date.distantFuture
        }
    }
    
    
    func endScrollMethod(_ ratio: CGFloat) {
        if ratio <= 0.7 {
            if self.currentPage - 1 < 0 {
                self.currentPage = self.imageArr.count - 1
            } else {
                self.currentPage -= 1
            }
        }
        if ratio >= 1.3 {
            if self.currentPage == self.imageArr.count - 1 {
                self.currentPage = 0
            }
            else {
                self.currentPage += 1
            }
        }
        self.startTimer()
    }
    
    @objc func timerAction() {
        var count: Int = 0
        if self.imageUrlArr.count > 0 {
            count = self.imageUrlArr.count
        }
        
        else if self.imageArr.count > 0 {
            count = self.imageArr.count
        }
        let w = screen_width

        
        self.currentPage = self.currentPage + 1
        if self.currentPage == count {
            UIView.animate(withDuration: 0.5, animations: {
                self.scrollview.contentOffset = CGPoint(x: w * CGFloat(self.currentPage), y: 0)
            }) { (ok) in
                if ok {
                    self.scrollview.contentOffset = CGPoint(x: 0, y: 0)
                }
            }
            self.currentPage = 0
        }
        else {
            UIView.animate(withDuration: 0.5) {
                self.scrollview.contentOffset = CGPoint(x: w * CGFloat(self.currentPage), y: 0)
            }
        }
        self.pageControl.currentPage = self.currentPage
    }
}

extension JDFilmstripView: UIScrollViewDelegate {
    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        self.autoTimer?.invalidate()
        self.autoTimer = nil
    }
    
    func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        let ratio = scrollView.contentOffset.x/screen_width
        self.currentPage = Int(ratio)
        self.pageControl.currentPage = self.currentPage
        self.autoTimer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
//        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 1) {
//            self.startTimer()
//        }
    }
    
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        let ratio = scrollView.contentOffset.x/screen_width
        self.currentPage = Int(ratio)
        self.pageControl.currentPage = self.currentPage
    }
}

【JDView】

import UIKit
import SnapKit

class JDView: UIView {
    init() {
        super.init(frame:CGRect(x: 0, y: 0, width: 0, height: 0))
        self.backgroundColor = UIColor.white
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    /*
    // Only override draw() if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func draw(_ rect: CGRect) {
        // Drawing code
    }
    */

}