How To Add Navigate To New Screens Drawer In Flutter App

import 'package:flutter/material.dart';

void main(){
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: NavToNewPageDrawer()
    );
  }
}

class NavToNewPageDrawer extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.blue[900],
        title: Text("Navigate To New Screens Drawer"),
      ),
      drawer: Container(
        width: 250,
        child: Drawer(
          child: Container(
            color: Colors.blue[900],
            child: Align(
              alignment: Alignment.bottomCenter,
              child: Container(
                child: ListView(padding: EdgeInsets.all(10.0), children: [
                  ListTile(
                    leading: Icon(Icons.home,color: Colors.white,),
                    title: Text("First Screen",style: TextStyle(color: Colors.white)),
                    onTap: () {
                      Navigator.of(context).push(
                          MaterialPageRoute<Null>(builder: (BuildContext context) {
                            return new FirstScreen();
                          }));
                    },
                  ),
                  ListTile(
                    leading: Icon(Icons.home,color: Colors.white,),
                    title: Text("Second Screen",style: TextStyle(color: Colors.white)),
                    onTap: () {
                      Navigator.of(context).push(
                          MaterialPageRoute<Null>(builder: (BuildContext context) {
                            return new SecondScreen();
                          }));
                    },
                  )
                ]),
              ),
            ),
          ),
        ),
      ),
      body: Center(
        child: Text('Main Body'),
      ),
    );
  }
}

class FirstScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("First Screen"),
      ),
      body: Center(
        child: RaisedButton(
          color: Colors.blue[900],
          child: Text("Go Back",style: TextStyle(color: Colors.white)),
          onPressed: () {
            Navigator.of(context).pop();
          },
        ),
      ),
    );
  }
}

class SecondScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Second Screen"),
      ),
      body: Center(
        child: RaisedButton(
          color: Colors.blue[900],
          child: Text("Go Back",style: TextStyle(color: Colors.white),),
          onPressed: () {
            Navigator.of(context).pop();
          },
        ),
      ),
    );
  }
}