按键重新启动UIActivityIndicator

import UIKit

class ViewController: UIViewController {
    var activityIndicator: UIActivityIndicatorView!
    var restartButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建UIActivityIndicator
        activityIndicator = UIActivityIndicatorView(style: .large)
        activityIndicator.center = view.center
        view.addSubview(activityIndicator)
        
        // 创建重新启动按钮
        restartButton = UIButton(type: .system)
        restartButton.setTitle("重新启动", for: .normal)
        restartButton.frame = CGRect(x: 0, y: 0, width: 200, height: 50)
        restartButton.center = CGPoint(x: view.center.x, y: view.center.y + 100)
        restartButton.addTarget(self, action: #selector(restartButtonTapped), for: .touchUpInside)
        view.addSubview(restartButton)
    }
    
    @objc func restartButtonTapped() {
        // 重新启动UIActivityIndicator的动画效果
        activityIndicator.startAnimating()
    }
}