在iOS5中使用UISegmentedControl切换ViewControllers

import UIKit

class ViewController: UIViewController {
    var segmentedControl: UISegmentedControl!
    var viewControllers: [UIViewController] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建UISegmentedControl
        segmentedControl = UISegmentedControl(items: ["First", "Second", "Third"])
        segmentedControl.frame = CGRect(x: 50, y: 100, width: 200, height: 30)
        segmentedControl.selectedSegmentIndex = 0
        segmentedControl.addTarget(self, action: #selector(segmentedControlValueChanged), for: .valueChanged)
        view.addSubview(segmentedControl)
        
        // 创建视图控制器
        let firstViewController = FirstViewController()
        let secondViewController = SecondViewController()
        let thirdViewController = ThirdViewController()
        
        // 将视图控制器添加到数组中
        viewControllers = [firstViewController, secondViewController, thirdViewController]
        
        // 显示初始视图控制器
        displayViewController(at: 0)
    }
    
    @objc func segmentedControlValueChanged() {
        let selectedIndex = segmentedControl.selectedSegmentIndex
        displayViewController(at: selectedIndex)
    }
    
    func displayViewController(at index: Int) {
        // 移除当前显示的视图控制器
        let currentViewController = children.first
        currentViewController?.willMove(toParent: nil)
        currentViewController?.view.removeFromSuperview()
        currentViewController?.removeFromParent()
        
        // 添加新的视图控制器
        let newViewController = viewControllers[index]
        addChild(newViewController)
        newViewController.view.frame = CGRect(x: 0, y: 150, width: view.frame.width, height: view.frame.height - 150)
        view.addSubview(newViewController.view)
        newViewController.didMove(toParent: self)
    }
}

class FirstViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .red
    }
}

class SecondViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .green
    }
}

class ThirdViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .blue
    }
}