如何在组件中监听App前后台切换？

onWindowStageCreate(windowStage: window.WindowStage) {  
  // Main window is created, set main page for this ability  
  hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');  
  windowStage.loadContent('pages/AppGeoLocation', (err, data) => {  
    if (err.code) {  
      hilog.error(0x0000, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err) ?? '');  
      return;  
    }  
    windowStage.getMainWindowSync().on("windowEvent", (data) => {  
      if (data == window.WindowEventType.WINDOW_SHOWN) {  
        console.log("App is in Foreground")  
      }  
      else if (data == window.WindowEventType.WINDOW_HIDDEN) {  
        console.log("App is in Background")  
      }  
    })  
    hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? '');  
  });  
}