title: Navigator from MaterialApp builder
body: <p>I'm trying to embed my whole App into an AppBar and a Footer.
  So I tried giving a custom Builder to my MaterialApp which look like this (I replaced the footer and the app bar by a button for clarity)</p>
  
  <pre><code>import 'package:epicture/scenes/Landing.dart';
  import 'package:flutter/material.dart';
  
  void main() =&gt; runApp(MyApp());
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'My App',
        initialRoute: '/',
        builder: (context, child) =&gt; Container(
            child: FlatButton(
                  child: Text('Click me'),
                  onPressed: () =&gt; Navigator.of(context).pushNamed('/app'),
        )),
        // In my current code
        builder: (context, child) =&gt; Embedder(child),
        routes: &lt;String, WidgetBuilder&gt;{
          '/': (context) =&gt; Landing(),
          '/app': (context) =&gt; Text('My App !'),
        },
      );
    }
  }
  </code></pre>
  
  <p>But on press of the 'Click me' button, an error is raised saying that the context doesn't have a Navigator</p>
  
  <p><code>the context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget</code></p>
  
  <p>But actually, the button is a footer that can be clicked to change page from every page.</p>
  
  <p>I would like to know how to have access to the navigator from the custom builder and if I simply head toward the wrong way for having the same pattern in every page of my application (Footer + header)</p>