Is there a way to detect focus and unfocus of a tab in the viewmodel of the view?

[m1dst]

  <tabs:LazyView
      x:Name="AboutTabView"
      x:TypeArguments="mainTabs:TabAbout"
      Animate="False"
      BindingContext="{Binding AboutViewModel}" />

I can't seem to find a command or event that allows me to detect when a tab is being shown or not. There are some events that seemed to be what I wanted but they never got triggered. (Focused and Unfocused).

EG:

<tabs:LazyView
    x:Name="AboutTabView"
    x:TypeArguments="mainTabs:TabAbout"
    Animate="False"
    BindingContext="{Binding AboutViewModel}"
    Focused="AboutTabView_Focused" />

I'm having to hack it by monitoring the IsSelected property of the MaterialUnderlinedTabItem. There must be a better way.

private void AboutTabItem_PropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
{
    if (e.PropertyName == "IsSelected")
    {
        var viewModel = (AboutViewModel)AboutTabView.BindingContext;
        if (AboutTabItem.IsSelected)
        { viewModel.Focused.Execute(null); }
        else
        { viewModel.Unfocused.Execute(null); }
    }
}

I have some code which I only want to run whilst the tab is visible as it is quite expensive.