问UIScrollview在一张图片前停止

EN

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var mainscrollview: UIScrollView!
    var imageArray = [UIImage]()
    
    override func viewDidLoad() {
        super.viewDidLoad()
  
        mainscrollview.frame = view.frame
        
        imageArray = [#imageLiteral(resourceName: "goku"), #imageLiteral(resourceName: "boruto"), #imageLiteral(resourceName: "tail"), #imageLiteral(resourceName: "sage"),#imageLiteral(resourceName: "tobi")]
        
        for i in 0..<imageArray.count{
            let imageView = UIImageView()
            imageView.image = imageArray[i]
            imageView.contentMode = .scaleAspectFit
            let xPosition = self.view.frame.width * CGFloat(i)
            imageView.frame = CGRect(x: xPosition, y: 0, width: self.mainscrollview.frame.width,height: self.mainscrollview.frame.height)
            mainscrollview.contentSize.width = mainscrollview.frame.width * CGFloat(i + 1)
            mainscrollview.addSubview(imageView)
        }
    }
}