import UIKit

class ViewController: UIViewController,UIScrollViewDelegate {
    var scrollView:UIScrollView?
    var picArr:[String]?
    var pageControl:UIPageControl?
    
    
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        picArr = ["java.png","scala.png","swift.png"]
        scrollView = UIScrollView(frame: CGRect(x: 0, y: 0, width: self.view.bounds.width, height: self.view.bounds.height))
        self.view.addSubview(scrollView!)
        scrollView?.delegate = self
        //设置内容大小
        scrollView?.contentSize = CGSize(width: self.view.bounds.width*3, height: self.view.bounds.height)
        //设置不显示滚动条
        scrollView?.showsVerticalScrollIndicator = false
        scrollView?.showsHorizontalScrollIndicator = false
        //滚动时只能停留到某一页
        scrollView?.isPagingEnabled = true
        
        //for循环,枚举
        for (seg,str) in (self.picArr?.enumerated())! {
            let img = UIImageView(image: UIImage(named: str))
            img.frame = CGRect(x: CGFloat(seg)*self.view.bounds.width, y: 0, width: self.view.bounds.width, height: self.view.bounds.height)
            scrollView?.addSubview(img)
        }
        pageControl = UIPageControl(frame: CGRect(x: 80, y: self.view.bounds.height-50, width: 80, height: 30))
        pageControl?.currentPage = 0
        pageControl?.numberOfPages = (self.picArr?.count)!
        pageControl?.addTarget(self, action: #selector(pageControlClick(_ :)), for: .valueChanged)
        
        self.view.addSubview(pageControl!)
        
        
        // Do any additional setup after loading the view, typically from a nib.
        
        
    }
    func pageControlClick(_ page:UIPageControl)
    {
        //根据点击的页数，计算scrollView需要显示的偏移量
        var frame = scrollView?.frame
        frame?.origin.x = (frame?.size.width)! * CGFloat(page.currentPage)
        frame?.origin.y = 0
        //展现当前页面内容
        scrollView?.scrollRectToVisible(frame!, animated:true)
        
    }


    //减速停止的时候开始执行
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        //通过scrollView内容的偏移计算当前显示的是第几页
        let page = Int(scrollView.contentOffset.x / scrollView.frame.size.width)
        //设置pageController的当前页
        self.pageControl?.currentPage = page
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}