是否在AVPLayerViewController中添加活动指标？(注:当视频处于全屏模式时)

import AVKit

class PlayerViewController: AVPlayerViewController {
    private var activityIndicator: UIActivityIndicatorView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建活动指示器
        activityIndicator = UIActivityIndicatorView(style: .whiteLarge)
        activityIndicator.color = .gray
        activityIndicator.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(activityIndicator)
        
        // 设置活动指示器的约束
        NSLayoutConstraint.activate([
            activityIndicator.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            activityIndicator.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        ])
    }
    
    func startLoading() {
        // 启动活动指示器
        activityIndicator.startAnimating()
    }
    
    func stopLoading() {
        // 停止活动指示器
        activityIndicator.stopAnimating()
    }
    
    // 在视频加载开始之前调用startLoading()方法，在视频加载完成或发生错误时调用stopLoading()方法
}