title: route on tab leads to Black Screen
body: <p>I defined the ontap method to navigate to SecondRoute class but it leads to the black screen.to resolve this issue I also replace the materialApp with Scaffold but didn't find luck </p>
  
  <pre><code>
  class FirstMain extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        body:TabviewWidget(),
        drawer: Drawer(
  
          child: ListView(
            children: &lt;Widget&gt;[
  
              ListTile(
                title: Text('Item 2'),
                onTap: () {
                  Navigator.push(
                context,
                MaterialPageRoute(builder: (context) =&gt; SecondRoute()),
              );
  
                },
              ),
            ],
          ),
        ),
  
      );
  
    }
  }
  
  class SecondRoute extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text("Second Route"),
        ),
        body: Center(
          child: RaisedButton(
            onPressed: () {
              Navigator.pop(context);
            },
            child: Text('Go back!'),
          ),
        ),
      );
    }
  }
  </code></pre>
  
  <p>I expected to open SecondRoute but appears black screen</p>