HarmonyOS 音频管理-监听音量变化无反应

@Component 
struct Index { 
  private audioManager = audio.getAudioManager(); 
  private audioVolumeManager = this.audioManager.getVolumeManager(); 
  aboutToAppear(): void { 
    console.info(`VolumeType of stream:--1-- `); 
    this.audioVolumeManager.on('volumeChange', (volumeEvent) => { 
      console.info(`VolumeType of stream:--2-- `); 
      console.info(`VolumeType of stream: ${volumeEvent.volumeType} `); 
      console.info(`VolumeType Volume level: ${volumeEvent.volume} `); 
      console.info(`VolumeType Whether to updateUI: ${volumeEvent.updateUi} `); 
    }); 
  }