Page Lifecycle

I'm trying to override 2 Xamarin.Form Page lifecyle methods (OnAppearing() and OnDisappearing()), but it doesn't appear to be working.

`

    protected override void OnAppearing()
    {            
        base.OnAppearing();
        System.Diagnostics.Debug.WriteLine("*****Here*****");
    }

    protected override void OnDisappearing()
    {            
        base.OnDisappearing();
        System.Diagnostics.Debug.WriteLine("*****Gone*****");
    }

`

Basically, I want to be able to detect when an app is going to the foreground/background. Is there a way to do this using Xamarin.Forms Pages?