Swift实现无限轮播效果_Swift

从今天开始，我学习的重点开始转向Swift，并且会分享一些自己学习的心得体会，今天给大家带来的的是无限轮播。广告页的无限轮播是非常常见的一个功能，大多数APP都有，大多数程序员也都实现过，今天我们用Swift实现一下。项目地址

图片切换我们可以选择的基本控件有两个UIScrollView 和 UICollectionView，这次我们选择UICollectionView；既然是轮播，就会用到Timer。所以，我们这次主要应用的知识点为UICollectionView 和 Timer；

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									import UIKit

									class CycleScrollView: UIView, UICollectionViewDelegate,UICollectionViewDataSource {

									  var bottomView : UICollectionView?

									  var width : CGFloat?

									  var height : CGFloat?

									  var timer : Timer?

									  override init(frame: CGRect){

									    super.init(frame: frame)

									    // 1.设置背景色

									    self.backgroundColor = UIColor.clear

									    // 2.设置宽高

									    width = self.frame.size.width

									    height = self.frame.size.height

									    // 3.添加bottomView

									    setupBottomView()

									    // 4.添加定时器

									    setupTimer()

									  }

									  required init?(coder aDecoder: NSCoder) {

									    fatalError("init(coder:) has not been implemented")

									  }

									  func setupBottomView() {

									    // 5.设置collectionView的布局

									    let flowLayout = UICollectionViewFlowLayout();

									    flowLayout.itemSize = self.bounds.size

									    flowLayout.minimumLineSpacing = 0;

									    flowLayout.minimumInteritemSpacing = 0;

									    flowLayout.scrollDirection = UICollectionViewScrollDirection.horizontal;

									    bottomView = UICollectionView.init(frame: self.bounds, collectionViewLayout: flowLayout)

									    self.addSubview(bottomView!);

									    // 6.设置collectionView的尺寸

									    bottomView?.contentSize = CGSize(width:width! * CGFloat(4),height:height!)

									    // 7.分页

									    bottomView?.isPagingEnabled = true

									    // 8.去掉滚动条

									    bottomView?.showsVerticalScrollIndicator = false

									    bottomView?.showsHorizontalScrollIndicator = false

									    // 9.设置代理

									    bottomView?.delegate = self

									    bottomView?.dataSource = self

									    // 10.注册cell

									    bottomView?.register(UICollectionViewCell().classForCoder, forCellWithReuseIdentifier: "ID");

									    if #available(iOS 10.0, *) {

									      // 11.预加载

									      bottomView?.isPrefetchingEnabled = true

									    } else {

									      // Fallback on earlier versions

									    }

									  }

									  func setupTimer() {

									    // 12.实例化定时器

									    timer = Timer.init(timeInterval: 2, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true);

									    RunLoop.main.add(timer!, forMode: RunLoopMode.defaultRunLoopMode);

									    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 2) {

									      self.timer?.fire();

									    }

									  }

									  func timerAction() {

									    var contentOffsetX = (self.bottomView?.contentOffset.x)! + self.frame.size.width

									    if contentOffsetX > self.frame.size.width * 3 {

									      // 当前视图显示的是第三个的时候，设置bottomView的偏移量为0

									      self.bottomView?.contentOffset = CGPoint(x:0,y:0)

									      contentOffsetX = self.frame.size.width

									    }

									     self.bottomView?.setContentOffset(CGPoint(x:contentOffsetX,y:0), animated: true)

									  }

									  // 重写removeFromSuperview方法，用于删除定时器，否则定时器一直存在，浪费内存

									  override func removeFromSuperview() {

									    timer?.invalidate()

									    timer = nil

									    super.removeFromSuperview()

									  }

									  // Mark:UICollectionViewDataSource

									  // 设置Itmes

									  func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

									    return 4;

									  }

									  // 设置cell

									  func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

									    let cell : UICollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "ID", for: indexPath)

									    for view : UIView in cell.contentView.subviews {

									      view.removeFromSuperview()

									    }

									    let imageView = UIImageView.init(frame: cell.contentView.bounds)

									    if indexPath.row < 3 {

									      imageView.image = UIImage.init(named: String(indexPath.row))

									    } else {

									      imageView.image = UIImage.init(named: String(0))

									    }

									    cell.contentView.addSubview(imageView)

									    return cell;

									  }

									  // Mark:UICollectionViewDelegate

									  // 点击方法

									  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

									    print("您点击了第 \(indexPath.row == 3 ? 0 : indexPath.row) 个");

									  }

									}