如何在swift中创建自定义选项卡栏？

import UIKit

class ViewController: UIViewController {
    
    let containerView = UIView()
    let tabButton1 = UIButton()
    let tabButton2 = UIButton()
    let tabButton3 = UIButton()
    
    let contentViewController1 = UIViewController()
    let contentViewController2 = UIViewController()
    let contentViewController3 = UIViewController()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置容器视图的frame
        containerView.frame = CGRect(x: 0, y: 20, width: view.frame.width, height: view.frame.height - 20)
        view.addSubview(containerView)
        
        // 设置选项卡按钮的frame和样式
        tabButton1.frame = CGRect(x: 0, y: 0, width: containerView.frame.width / 3, height: 50)
        tabButton1.setTitle("Tab 1", for: .normal)
        tabButton1.backgroundColor = UIColor.lightGray
        tabButton1.addTarget(self, action: #selector(tabButtonTapped(_:)), for: .touchUpInside)
        containerView.addSubview(tabButton1)
        
        tabButton2.frame = CGRect(x: containerView.frame.width / 3, y: 0, width: containerView.frame.width / 3, height: 50)
        tabButton2.setTitle("Tab 2", for: .normal)
        tabButton2.backgroundColor = UIColor.lightGray
        tabButton2.addTarget(self, action: #selector(tabButtonTapped(_:)), for: .touchUpInside)
        containerView.addSubview(tabButton2)
        
        tabButton3.frame = CGRect(x: containerView.frame.width / 3 * 2, y: 0, width: containerView.frame.width / 3, height: 50)
        tabButton3.setTitle("Tab 3", for: .normal)
        tabButton3.backgroundColor = UIColor.lightGray
        tabButton3.addTarget(self, action: #selector(tabButtonTapped(_:)), for: .touchUpInside)
        containerView.addSubview(tabButton3)
        
        // 设置自定义视图控制器的frame和内容
        contentViewController1.view.frame = CGRect(x: 0, y: 50, width: containerView.frame.width, height: containerView.frame.height - 50)
        contentViewController1.view.backgroundColor = UIColor.red
        containerView.addSubview(contentViewController1.view)
        
        contentViewController2.view.frame = CGRect(x: 0, y: 50, width: containerView.frame.width, height: containerView.frame.height - 50)
        contentViewController2.view.backgroundColor = UIColor.green
        containerView.addSubview(contentViewController2.view)
        
        contentViewController3.view.frame = CGRect(x: 0, y: 50, width: containerView.frame.width, height: containerView.frame.height - 50)
        contentViewController3.view.backgroundColor = UIColor.blue
        containerView.addSubview(contentViewController3.view)
        
        // 默认显示第一个自定义视图控制器
        showContentViewController(contentViewController1)
    }
    
    @objc func tabButtonTapped(_ sender: UIButton) {
        if sender == tabButton1 {
            showContentViewController(contentViewController1)
        } else if sender == tabButton2 {
            showContentViewController(contentViewController2)
        } else if sender == tabButton3 {
            showContentViewController(contentViewController3)
        }
    }
    
    func showContentViewController(_ viewController: UIViewController) {
        contentViewController1.view.isHidden = true
        contentViewController2.view.isHidden = true
        contentViewController3.view.isHidden = true
        
        viewController.view.isHidden = false
    }
}