title: Nav bar Indicator for which tab is selected isn't working
body: <p>this is my second thread to this Topic, this time I will ad a picture and the full code.
  The nav bar is working but I want an indicator on which is pressed (the text under the icon is already scaling up a bit but thats not enough)
  I want hat the segment which is pressed has a more light background then the others.
  How is that possible? I'm really new to Flutter and currently this is the only programming language which is complete confusing for me. <a href="https://i.stack.imgur.com/K8ueX.jpg" rel="nofollow noreferrer">screenshot</a>
  In the code, I just have included an icon font (font awesome) and 3 pages which the nav bar directs to. (neu, beliebt, profil)</p>
  
  <pre><code>import 'package:flutter/material.dart';
  import 'package:font_awesome_flutter/font_awesome_flutter.dart';
  import 'Neu.dart';
  import 'Beliebt.dart';
  import 'Profil.dart';
  
  void main() =&gt; runApp(new MyApp());
  
  class MyApp extends StatefulWidget {
    @override
    State&lt;StatefulWidget&gt; createState() {
      return MyAppState();
    }
  }
  
  class MyAppState extends State&lt;MyApp&gt; {
    int _selectedTab = 0;
    final _pageOptions = [
      NeuPage(),
      BeliebtPage(),
      ProfilPage(),
    ];
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        theme: ThemeData(
            primaryColor: Colors.deepOrangeAccent,
            primaryTextTheme: TextTheme(
              title: TextStyle(color: Colors.white),
            )),
        home: Scaffold(
          appBar: AppBar(
            title: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                    Image.asset(
                   'assets/logo_straight.png',
                    fit: BoxFit.contain,
                    height: 32,
                ),
              ],
            ),
          ),
  
  
          body: _pageOptions[_selectedTab],
  
          bottomNavigationBar: BottomNavigationBar(
            currentIndex: _selectedTab,
            backgroundColor: Colors.deepOrangeAccent,
            onTap: (int index) {
              setState(() {
                _selectedTab = index;
              });
            },
            items: [
              BottomNavigationBarItem(
                icon: Icon(FontAwesomeIcons.quoteRight, color: Colors.white),
                title: Text('Neu', style: TextStyle(color: Colors.white),
                )
              ),
              BottomNavigationBarItem(
                icon: Icon(Icons.whatshot, color: Colors.white),
                title: Text('Beliebt', style: TextStyle(color: Colors.white),
                )
              ),
              BottomNavigationBarItem(
                icon: Icon(Icons.account_circle, color: Colors.white),
                title: Text('Profil', style: TextStyle(color: Colors.white),
                )
              ),
            ],
          ),
        ),
      );
    }
  }
  </code></pre>