HarmonyOS 调用 getWindowAvoidArea 方法无法获取到底部导航栏高度

nWindowStageCreate(windowStage: window.WindowStage): void {  
    // Main window is created, set main page for this ability  
    hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');  
    let windowClass: window.Window;  
    windowStage.getMainWindow((err, data) => {  
      // 1.获取应用主窗口  
      windowClass = data;  
      // 2.设置导航栏、状态栏显示。  
      // 3.设置全屏  
      windowClass.setWindowLayoutFullScreen(true).then(() => {  
      })  
      // 4.获取底部导航栏高度，此时的高度单位是px  
      let navigationHeight = windowClass.getWindowAvoidArea(window.AvoidAreaType.TYPE_SYSTEM).bottomRect.height  
      let navHeightVp = px2vp(navigationHeight)  
      console.error(`获取导航栏高度：${navigationHeight}--${navHeightVp}`)  
    })  
  }