UIScrollView循环滚动

循环滚动原理很简单，注释中可以看到

////  ViewController.swift//import UIKitclass ViewController: UIViewController,UIScrollViewDelegate {        let _widthSV:CGFloat = UIScreen.mainScreen().bounds.size.width - 20        let _heightSV:CGFloat = 200        let _scrollView:UIScrollView = UIScrollView()        //图片循环滚动原理    //两边各加一张图片，按照 1  2  3  4  5  6 顺序对应下面六张图片    //当滚动至6时触发函数 scrollViewDidScroll 中的条件语句 s2 让画面在感觉不到的情况下跳转至2    //当滚动至1时触发函数 scrollViewDidScroll 中的条件语句 s1 让画面在感觉不到的情况下跳转至5    let picNames:NSArray = NSArray(array: ["pic4", "pic1", "pic2", "pic3", "pic4", "pic1"])        override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view, typically from a nib.        self.view.addSubview(_scrollView)                _scrollView.frame = CGRectMake(10, 50, _widthSV, _heightSV)                for var i = 0; i < picNames.count; i++ {            let nameStr:NSString = picNames[i] as! NSString                        let imageView:UIImageView = UIImageView(frame: CGRectMake(CGFloat(i) * _widthSV, 0, _widthSV, _heightSV))                        let imageFileStr:NSString = NSBundle.mainBundle().pathForResource(nameStr as String, ofType: "jpg")!                        imageView.image = UIImage(contentsOfFile: imageFileStr as String)                        _scrollView.addSubview(imageView)        }                _scrollView.contentSize = CGSizeMake(CGFloat(picNames.count) * _widthSV, 0)        _scrollView.pagingEnabled = true        _scrollView.contentInset = UIEdgeInsetsZero        _scrollView.setContentOffset(CGPointMake(_widthSV, 0), animated: false)        _scrollView.delegate = self        _scrollView.showsHorizontalScrollIndicator = false //不显示滚动条    }        func scrollViewDidScroll(scrollView: UIScrollView) {        let point = scrollView.contentOffset        if Int(point.x) == 0 {   //s1            scrollView.setContentOffset(CGPointMake(_widthSV * CGFloat(picNames.count - 2), 0), animated: false)        }else if Int(point.x) == Int(_widthSV * CGFloat(picNames.count - 2 + 1)) {  // s2            scrollView.setContentOffset(CGPointMake(_widthSV, 0), animated: false)        }    }        override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }}