Xcode 10 -以编程方式添加按钮时，滚动视图不允许滚动

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建滚动视图
        let scrollView = UIScrollView(frame: view.bounds)
        scrollView.contentSize = CGSize(width: view.bounds.width, height: view.bounds.height * 2)
        scrollView.isScrollEnabled = true
        
        // 创建按钮
        let button = UIButton(type: .system)
        button.setTitle("点击按钮", for: .normal)
        button.frame = CGRect(x: 100, y: 100, width: 200, height: 50)
        
        // 将按钮添加到滚动视图
        scrollView.addSubview(button)
        
        // 将滚动视图添加到视图控制器的视图中
        view.addSubview(scrollView)
    }
}