Swift - 滚动视图（UIScrollView）的用法

let scrollView = UIScrollView()
scrollView.frame = self.view.bounds
let imageView = UIImageView(image:UIImage(named:"bigpic"))
scrollView.contentSize = imageView.bounds.size
scrollView.addSubview(imageView)
self.view.addSubview(scrollView)

2，获取滚动视图移动的x,y坐标
通过scrollView.contentOffset.x与scrollView.contentOffset.y我们可以取到移动的偏移位置

import UIKit

class ViewController: UIViewController, UIScrollViewDelegate {
    
    var scrollView:UIScrollView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        scrollView = UIScrollView()
        //设置代理
        scrollView.delegate = self
        scrollView.frame = self.view.bounds
        let imageView = UIImageView(image:UIImage(named:"bigpic.jpg"))
        scrollView.contentSize = imageView.bounds.size
        scrollView.addSubview(imageView)
        self.view.addSubview(scrollView)
    }
    
    //视图滚动中一直触发
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        print("x:\(scrollView.contentOffset.x) y:\(scrollView.contentOffset.y)")
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

3，手势放大缩小
要实现放大缩小功能，需要指定UIScrollView的允许缩放最大比例和最小比例（默认都是是1.0）。
同时delegate属性指定一个委托类，委托类要继承UIScrollViewDelegate协议，并在委托类中实现viewForZooming方法。
（注：在模拟器中测试，需要按住option键再拖动内容）

scrollView.minimumZoomScale = 0.1 //最小比例
scrollView.maximumZoomScale = 3 //最大比例
scrollView.delegate = self

func viewForZooming(in scrollView: UIScrollView) -> UIView? {
    for subview : AnyObject in scrollView.subviews {
        if subview.isKind(of: UIImageView.self) {
            return subview as? UIView
        }
    }
    return nil
}