viewWillLayoutSubviews

override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        setZoomScaleFor(scrollViewSize: scrollView.bounds.size)
        if scrollView.zoomScale < scrollView.minimumZoomScale {
            scrollView.zoomScale = scrollView.minimumZoomScale
        }
        recenterImage()
    }

自動(dòng)布局

    flexibleLeftMargin  自動(dòng)調(diào)整view與父視圖左邊距徘层，保證右邊距不變
     flexibleWidth       自動(dòng)調(diào)整view的寬度氓鄙，保證左邊距和右邊距不變
     flexibleRightMargin 自動(dòng)調(diào)整view與父視圖右邊距，以保證左邊距不變
     flexibleTopMargin   自動(dòng)調(diào)整view與父視圖上邊距，以保證下邊距不變
     flexibleHeight      自動(dòng)調(diào)整view的高度邀跃，以保證上邊距和下邊距不變
     flexibleBottomMargin自動(dòng)調(diào)整view與父視圖的下邊距坛猪，以保證上邊距不變

        scrollView.autoresizingMask = [.flexibleWidth,.flexibleHeight]

<li><h1>學(xué)習(xí)代碼:<h1></li>

ViewController.swift

import UIKit

let YHRect = UIScreen.main.bounds
let YHHeight = YHRect.size.height
let YHWidth = YHRect.size.width

class ViewController: UIViewController {
    
    
    let scrollView = UIScrollView(frame: YHRect)
    let imageView = UIImageView(image: UIImage(named: "steve"))
    

    override func viewDidLoad() {
        super.viewDidLoad()
        setupBG()
        setupScrollView()
        setZoomScaleFor(scrollViewSize: scrollView.bounds.size)
        scrollView.zoomScale = scrollView.minimumZoomScale
        recenterImage()
    }
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .lightContent
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        setZoomScaleFor(scrollViewSize: scrollView.bounds.size)
        if scrollView.zoomScale < scrollView.minimumZoomScale {
            scrollView.zoomScale = scrollView.minimumZoomScale
        }
        recenterImage()
    }
    
    
    //背景
    func setupBG() {
        view.layer.contents = UIImage(named: "steve")?.cgImage
        let visual = UIVisualEffectView(effect: UIBlurEffect(style: .dark))
        visual.frame = YHRect
        view.addSubview(visual)
    }
    //scrollview
    func setupScrollView() {
        /*自動(dòng)布局
         flexibleLeftMargin  自動(dòng)調(diào)整view與父視圖左邊距，保證右邊距不變
         flexibleWidth       自動(dòng)調(diào)整view的寬度污秆，保證左邊距和右邊距不變
         flexibleRightMargin 自動(dòng)調(diào)整view與父視圖右邊距劈猪，以保證左邊距不變
         flexibleTopMargin   自動(dòng)調(diào)整view與父視圖上邊距，以保證下邊距不變
         flexibleHeight      自動(dòng)調(diào)整view的高度良拼，以保證上邊距和下邊距不變
         flexibleBottomMargin自動(dòng)調(diào)整view與父視圖的下邊距战得，以保證上邊距不變
         */
        scrollView.autoresizingMask = [.flexibleWidth,.flexibleHeight]
        scrollView.backgroundColor = .clear
        scrollView.contentSize = imageView.bounds.size
        scrollView.delegate = self
        
        scrollView.addSubview(imageView)
        view.addSubview(scrollView)
    }
    //設(shè)置縮放
    func setZoomScaleFor(scrollViewSize: CGSize) {
        let imageSize = imageView.bounds.size
        let widthScale = scrollViewSize.width/imageSize.width
        let heightScale = scrollViewSize.height/imageSize.height
        let minimunScale = min(widthScale,heightScale)
        
        scrollView.minimumZoomScale = minimunScale
        scrollView.maximumZoomScale = 3.5
    }
    //重新定位image
    func recenterImage() {
        let scrollViewSize = scrollView.bounds.size
        let imageViewSize = imageView.frame.size
        let horizontalSpace = imageViewSize.width < scrollViewSize.width ? (scrollViewSize.width - imageViewSize.width) / 2.0 : 0
        let verticalSpace = imageViewSize.height < scrollViewSize.height ? (scrollViewSize.height - imageViewSize.width) / 2.0 :0
        
        scrollView.contentInset = UIEdgeInsetsMake(verticalSpace, horizontalSpace, verticalSpace, horizontalSpace)
    }
}

extension ViewController: UIScrollViewDelegate {
    //要縮放時(shí)調(diào)用，返回需要縮放的view
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }
    //縮放后調(diào)用
    func scrollViewDidZoom(_ scrollView: UIScrollView) {
        recenterImage()
    }
}