切换到第二个UIViewController时，无法保存或查看视频

// 创建AVCaptureSession对象
let captureSession = AVCaptureSession()

// 配置输入设备
guard let videoDevice = AVCaptureDevice.default(for: .video),
      let videoInput = try? AVCaptureDeviceInput(device: videoDevice),
      captureSession.canAddInput(videoInput) else {
    return
}
captureSession.addInput(videoInput)

// 配置输出设备
let fileOutput = AVCaptureMovieFileOutput()
if captureSession.canAddOutput(fileOutput) {
    captureSession.addOutput(fileOutput)
}

// 设置输出文件路径
let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
let outputURL = documentsDirectory.appendingPathComponent("output.mov")
fileOutput.startRecording(to: outputURL, recordingDelegate: self)

// 停止录制
fileOutput.stopRecording()

// 创建AVPlayer对象
let videoURL = // 视频文件URL
let player = AVPlayer(url: videoURL)

// 创建AVPlayerViewController对象并设置player属性
let playerViewController = AVPlayerViewController()
playerViewController.player = player

// 播放视频
present(playerViewController, animated: true) {
    playerViewController.player?.play()
}