title: How to deactivate or override the Android "BACK" button, in Flutter?
body: <p>Is there a way to deactivate the Android back button when on a specific page? </p>
  
  <pre><code>class WakeUpApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return new MaterialApp(
        title: "Time To Wake Up ?",
        home: new WakeUpHome(),
        routes: &lt;String, WidgetBuilder&gt;{
          '/pageOne': (BuildContext context) =&gt; new pageOne(),
          '/pageTwo': (BuildContext context) =&gt; new pageTwo(),
        },
      );
    }
  }
  </code></pre>
  
  <p>On pageOne I have a button to go to pageTwo: </p>
  
  <pre><code>new FloatingActionButton(
    onPressed: () {    
      Navigator.of(context).pushNamed('/pageTwo');
    },
  )
  </code></pre>
  
  <p>My problem is that if I press the Back arrow at the bottom of the android screen, I go back to pageOne. I would like this button to not show up at all. 
  Ideally, I would like to have no possible way out of this screen unless the user for example keeps his finger pressed on the screen for 5 seconds. (I am trying to write an App for toddlers, and would like only the parents to be able to navigate out of the particular screen). </p>