圆形UIScrollView

import UIKit

class CircularScrollView: UIScrollView, UIScrollViewDelegate {
    let circleLayer = CAShapeLayer()
    let circleRadius: CGFloat = 100.0
    let circleCenter = CGPoint(x: 100, y: 100)
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }
    
    func setup() {
        delegate = self
        showsVerticalScrollIndicator = false
        showsHorizontalScrollIndicator = false
        bounces = false
        isPagingEnabled = true
        contentSize = CGSize(width: circleRadius * 2, height: circleRadius * 2)
        
        let path = UIBezierPath(arcCenter: circleCenter, radius: circleRadius, startAngle: 0, endAngle: CGFloat.pi * 2, clockwise: true)
        circleLayer.path = path.cgPath
        circleLayer.fillColor = UIColor.clear.cgColor
        circleLayer.strokeColor = UIColor.black.cgColor
        circleLayer.lineWidth = 2.0
        layer.mask = circleLayer
    }
    
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        let offsetX = scrollView.contentOffset.x
        let offsetY = scrollView.contentOffset.y
        let centerX = circleCenter.x + offsetX
        let centerY = circleCenter.y + offsetY
        
        let path = UIBezierPath(arcCenter: CGPoint(x: centerX, y: centerY), radius: circleRadius, startAngle: 0, endAngle: CGFloat.pi * 2, clockwise: true)
        circleLayer.path = path.cgPath
    }
}