Routes not persisted when switching tabs about fluro HOT 6 CLOSED

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      bottomNavigationBar: new Material(
        child: new TabBar(
          controller: _tabController,
          tabs: <Widget>[
            new Tab(icon: new Icon(Icons.accessibility_new), text: 'Practice'),
            new Tab(icon: new Icon(Icons.video_library), text: 'Learn'),
            new Tab(icon: new Icon(Icons.headset), text: 'Listen'),
            new Tab(icon: new Icon(Icons.multiline_chart), text: 'Track'),
          ],
        ),
        color: Theme.of(context).primaryColor,
      ),
      body: new TabBarView(
        controller: _tabController,
        children: <Widget>[
          new MaterialApp(home: new Practice(), onGenerateRoute: Application.router.generator, theme: Theme.of(context), key: new PageStorageKey('PracticeTab')),
          new MaterialApp(home: new Learn(), onGenerateRoute: Application.router.generator, theme: Theme.of(context), key: new PageStorageKey('LearnTab')),
          new MaterialApp(home: new Listen(), onGenerateRoute: Application.router.generator, theme: Theme.of(context), key: new PageStorageKey('ListenTab')),
          new MaterialApp(home: new Track(), onGenerateRoute: Application.router.generator, theme: Theme.of(context), key: new PageStorageKey('TrackTab')),
        ],
      ),
    );
  }