UIScrollView带有居中的UIImageView

import UIKit

class ViewController: UIViewController {
    private let scrollView = UIScrollView()
    private let imageView = UIImageView()

    override func viewDidLoad() {
        super.viewDidLoad()

        setupScrollView()
        setupImageView()
    }

    private func setupScrollView() {
        scrollView.frame = view.bounds
        scrollView.delegate = self
        scrollView.minimumZoomScale = 1.0
        scrollView.maximumZoomScale = 3.0
        view.addSubview(scrollView)
    }

    private func setupImageView() {
        let image = UIImage(named: "example")
        imageView.image = image
        imageView.frame = CGRect(x: 0, y: 0, width: image?.size.width ?? 0, height: image?.size.height ?? 0)
        imageView.center = scrollView.center
        scrollView.addSubview(imageView)

        let horizontalInset = max((scrollView.bounds.width - imageView.bounds.width) / 2, 0)
        let verticalInset = max((scrollView.bounds.height - imageView.bounds.height) / 2, 0)
        scrollView.contentInset = UIEdgeInsets(top: verticalInset, left: horizontalInset, bottom: verticalInset, right: horizontalInset)

        scrollView.contentSize = imageView.bounds.size
    }
}

extension ViewController: UIScrollViewDelegate {
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }
}