HarmonyOS tabContent onPageShow 方法不生效，如何监听页面回到前台？

@Link @Watch('customShow') timer: Number  
customShow(){  
  this.getUIContext().getPromptAction().showToast({  
    message: "Home页面展示"  
  });  
}  
MainPage.ets  
@State HomeTimer: number = 0;  
Home({  
  timer:$HomeTimer  
})  
onPageShow() {  
  if (this.currentPageIndex == 0) { //Home  
    this.HomeTimer = this.timeStamp()  
  } else if(this.currentPageIndex == 1) {//Message  
  
  }  
}  
  
timeStamp(){  
  return new Date().getTime();  
}