scrollView的偏移和缩放、pageControl(小点)

cg```swift
class ViewController: UIViewController, UIScrollViewDelegate {

var scrollView: UIScrollView!
var redView: UIView!
var pageControl: UIPageControl!
override func viewDidLoad() {
    super.viewDidLoad()
    //创建scrollView
    scrollView = UIScrollView(frame: CGRect(x: 0, y: 100, width: self.view.frame.size.width, height: 200))
    scrollView.backgroundColor = UIColor.cyanColor()
    self.view.addSubview(scrollView)
    //在scrollview上添加两个标记View
    redView = UIView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
    redView.backgroundColor = UIColor.redColor()
    scrollView.addSubview(redView)
    let greenView = UIView(frame: CGRect(x: scrollView.frame.size.width - 50, y: scrollView.frame.size.height - 50, width: 50, height: 50))
    greenView.backgroundColor = UIColor.redColor()
    scrollView.addSubview(greenView)
    
    //UIScrollView能否滚动
    //1. scrollEnabled
    //2. contentSize: (0, 0) 内容大小，只有当内容尺寸超过本身尺寸时
    scrollView.contentSize = CGSize(width: scrollView.frame.size.width * 3, height: scrollView.frame.size.height)
    //设置内容距四周的距离(边框大小)
    scrollView.contentInset = UIEdgeInsetsMake(10, 0, 10, 0)
    //设置偏移量(向左、向上滚动为正)
    scrollView.contentOffset = CGPoint(x: 100, y: 0)
    //方向锁, 一次只允许一个方向滚动
    scrollView.directionalLockEnabled = true
    //弹性效果
    scrollView.bounces = false
    //水平滚动条
    scrollView.showsVerticalScrollIndicator = false
    //垂直滚动条
    scrollView.showsHorizontalScrollIndicator = false
    
    scrollView.delegate = self
    //最小缩放倍数
    scrollView.minimumZoomScale = 1
    //最大缩放倍数
    scrollView.maximumZoomScale = 5
    
    //小点处于控件中央
    pageControl = UIPageControl(frame: CGRect(x: 0, y: scrollView.frame.origin.y + scrollView.frame.size.height - 20, width: scrollView.frame.size.width, height: 20))
    //设置小点个数
    pageControl.numberOfPages = 3
    //设置当前小点颜色
    pageControl.currentPageIndicatorTintColor = UIColor.blueColor()
    //设置其余小点颜色
    pageControl.pageIndicatorTintColor = UIColor.yellowColor()
    self.view.addSubview(pageControl)
    //给小点添加点击事件,将点击小点的事件连接到scrollView上
    pageControl.addTarget(self, action: #selector(didChange(_:)), forControlEvents: .ValueChanged)
    
}

func didChange(sender: UIPageControl){
    let offset = CGPoint(x: scrollView.bounds.size.width * CGFloat(sender.currentPage), y: 0)
    //1. 没有动画效果

// scrollView.contentOffset = offset
//2. 有动画效果
// scrollView.setContentOffset(offset, animated: true)
//3. 将一个矩形区域设为可见
let rect = CGRect(x: offset.x, y: 0, width: scrollView.bounds.size.width, height: scrollView.bounds.size.height)
scrollView.scrollRectToVisible(rect, animated: true)
}

func scrollViewDidScroll(scrollView: UIScrollView) {
    //只要有位移就会持续调用
    print(scrollView.contentOffset)
}
func scrollViewWillBeginDragging(scrollView: UIScrollView) {
    print("begin dragging")
}
func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    print("结束拖动")
}
// 一般就只用下面两个函数
func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    if decelerate {
        print("开始减速")
    }
    else {
        print("无需减速")
        pageControl.currentPage = Int(scrollView.contentOffset.x / scrollView.bounds.size.width)
    }
}
func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
    print("停止减速")
    //把scrollView的偏移情况在小点上面显示
    pageControl.currentPage = Int(scrollView.contentOffset.x / scrollView.bounds.size.width)
}

//设置scrollview上要缩放的View, 返回值为View
func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
    return redView
}

}