使用swift 3中的计时器自动更改UIPageViewController中的页面？

import UIKit

class ViewController: UIViewController, UIPageViewControllerDataSource {

    var pageViewController: UIPageViewController!
    var timer: Timer!
    var currentIndex = 0
    var viewControllers: [UIViewController] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 初始化页面控制器
        pageViewController = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
        pageViewController.dataSource = self
        
        // 创建要显示的视图控制器
        let viewController1 = UIViewController()
        viewController1.view.backgroundColor = .red
        let viewController2 = UIViewController()
        viewController2.view.backgroundColor = .green
        let viewController3 = UIViewController()
        viewController3.view.backgroundColor = .blue
        
        // 将视图控制器添加到数组中
        viewControllers = [viewController1, viewController2, viewController3]
        
        // 设置初始显示的视图控制器
        pageViewController.setViewControllers([viewController1], direction: .forward, animated: true, completion: nil)
        
        // 将页面控制器添加到当前视图控制器中
        addChild(pageViewController)
        view.addSubview(pageViewController.view)
        pageViewController.didMove(toParent: self)
        
        // 启动计时器
        startTimer()
    }
    
    // 启动计时器
    func startTimer() {
        timer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(changePage), userInfo: nil, repeats: true)
    }
    
    // 切换页面
    @objc func changePage() {
        currentIndex += 1
        if currentIndex >= viewControllers.count {
            currentIndex = 0
        }
        let viewController = viewControllers[currentIndex]
        pageViewController.setViewControllers([viewController], direction: .forward, animated: true, completion: nil)
    }
    
    // MARK: - UIPageViewControllerDataSource
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let index = viewControllers.firstIndex(of: viewController) else {
            return nil
        }
        let previousIndex = index - 1
        if previousIndex < 0 {
            return viewControllers.last
        }
        return viewControllers[previousIndex]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let index = viewControllers.firstIndex(of: viewController) else {
            return nil
        }
        let nextIndex = index + 1
        if nextIndex >= viewControllers.count {
            return viewControllers.first
        }
        return viewControllers[nextIndex]
    }
    
    func presentationCount(for pageViewController: UIPageViewController) -> Int {
        return viewControllers.count
    }
    
    func presentationIndex(for pageViewController: UIPageViewController) -> Int {
        return currentIndex
    }
}