如何在UIKit中垂直放置两个UIViewController？

// ParentViewController.swift

import UIKit

class ParentViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建UIStackView作为容器视图
        let stackView = UIStackView()
        stackView.axis = .vertical
        stackView.alignment = .fill
        stackView.distribution = .fillEqually
        stackView.spacing = 10
        
        // 创建两个子视图控制器
        let childViewController1 = ChildViewController1()
        let childViewController2 = ChildViewController2()
        
        // 将子视图控制器添加为父视图控制器的子视图控制器
        addChild(childViewController1)
        addChild(childViewController2)
        
        // 将子视图添加到UIStackView中
        stackView.addArrangedSubview(childViewController1.view)
        stackView.addArrangedSubview(childViewController2.view)
        
        // 添加UIStackView到父视图
        view.addSubview(stackView)
        
        // 设置UIStackView的约束
        stackView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            stackView.topAnchor.constraint(equalTo: view.topAnchor),
            stackView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            stackView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            stackView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
    }
}