swift 4中的MPRemoteCommandCenter错误

我正在尝试将我的应用程序设置为使用MPRemoteCommandCenter。我从文档编程指南中得到了这个示例。我导入了AVFoundation,甚至尝试导入AVKIT,我发现了错误 使用未解析的标识符“MPRemoteCommandCenter” 。创建MPRemoteCommandCenter实例时。共享()。任何帮助都将不胜感激。

func setupRemoteTransportControls() {

    // Get the shared MPRemoteCommandCenter
    let commandCenter = MPRemoteCommandCenter.shared()   Error //**Use of unresolved identifier 'MPRemoteCommandCenter'**

    // Add handler for Play Command
    commandCenter.playCommand.addTarget { [unowned self] event in
        if self.audioPlayer.rate == 0.0 {
            self.audioPlayer.play()
            return .success
        }
        return .commandFailed
    }

    // Add handler for Pause Command
    commandCenter.pauseCommand.addTarget { [unowned self] event in
        if self.audioPlayer.rate == 1.0 {
            self.audioPlayer.pause()
            return .success
        }
        return .commandFailed
    }
}