利用ScrollView实现图片缩放

import UIKit

class ViewController: UIViewController,UIScrollViewDelegate {    var scrollView:UIScrollView!    var imageView:UIImageView!    override func viewDidLoad() {        super.viewDidLoad()        // 有导航栏的话加上这一句        self.automaticallyAdjustsScrollViewInsets = false        self.view.backgroundColor = UIColor.green        scrollView = UIScrollView.init(frame: self.view.bounds)        scrollView.delegate = self        ／／设置最大最小缩放倍数        scrollView.maximumZoomScale = 2        scrollView.minimumZoomScale = 1        scrollView.backgroundColor = UIColor.blue        imageView = UIImageView.init(frame: CGRect(x: 0, y: 0, width: self.view.frame.size.width, height: self.view.frame.size.width))        imageView.image = UIImage.init(named: "1")        imageView.backgroundColor = UIColor.red        scrollView.contentSize = imageView.frame.size        scrollView.addSubview(imageView)        imageView.center = scrollView.center        self.view.addSubview(scrollView)        imageView.isUserInteractionEnabled = true    }／**通过以下代理控制图片缩放**／    func viewForZooming(in scrollView: UIScrollView) -> UIView? {        return scrollView.subviews[0]    }    func scrollViewDidZoom(_ scrollView: UIScrollView) {        let offsetX = (scrollView.bounds.size.width > scrollView.contentSize.width) ? (scrollView.bounds.size.width - scrollView.contentSize.width) * 0.5 : 0.0        let offSetY = (scrollView.bounds.size.height > scrollView.contentSize.height) ? (scrollView.bounds.size.height - scrollView.contentSize.height) * 0.5 : 0.0        imageView.center = CGPoint(x: scrollView.contentSize.width * 0.5 + offsetX, y: scrollView.contentSize.height * 0.5 + offSetY)    }    override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }}

效果图