can Application.getRootView() called anywhere?

[fgroupindonesia]

i recently use a button that call certain function.

Let say this is my login\login-page.xml file contains :

<Page
    navigatingTo="onNavigatingTo"
    xmlns="http://schemas.nativescript.org/tns.xsd">

    <ActionBar>
        <NavigationButton visibility="hidden"></NavigationButton>
        <GridLayout columns="50, *">
            <Label class="action-bar-title" text="DaftarGigi" colSpan="2"/>
            <Label class="fas" text="&#xf0c9;" tap="onDrawerButtonTap"/>
        </GridLayout>
    </ActionBar>

    <StackLayout id="login-form-layout" backgroundColor="#3c495e" orientation="vertical"
    verticalAlignment="center" >
            <Image class="app-logo" src="~/images/logo.png" stretch="aspectFill" />
            <Label class="text-title" text="DAFTARGIGI" textWrap="true"/> 
            <Label class="text-subtitle" text="~ Platform Online untuk Manajemen Klinik Gigi ~" textWrap="true"/> 
            <TextField class="input-textfield" hint="Email" color="orangered" backgroundColor="lightyellow" />
            <TextField class="input-textfield" secure="true" hint="Password" color="orangered" backgroundColor="lightyellow" />
            <Button text="Login" tap="onVerify"></Button>
        
    </StackLayout>

    
</Page>

And the Button is actually calling my onVerify functions located inside login-page.js where it was located in the same directory as the previous file. And these are the code of the javascript :

export function onVerify(args){
  var page = args.object.page;
  var form = getViewById(page, "login-form-layout");
  page.frame.navigate({
    moduleName: 'home/home-page',
    clearHistory: true,
  });

  // but the code below didnt work!
  var parent = Application.getRootView();
  var menuUnlogged = getViewById(parent, "unlogged");
  var menuLogged = getViewById(parent, "logged-in");

  menuUnlogged.visibility = "collapse";
  menuLogged.visibility = "visible"; 
}

My purpose is that this button could get the reference of the parent view. And finding the layout there.
Then change the visibility to be shown or hidden. But the apps when i did click on the button giving me a crashed result. Saying that there is undefined variable on visibility.

May i know why it cant get the reference? So strange....

Wish anyone could help me out of this problem.