flutter: Another exception was thrown: Navigator operation requested with a context that does not include a Navigator.

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Center(
        child: RaisedButton(
          child: Text("Test"),
          onPressed: () {
              print('click-OK');
              Navigator.push(context,
                  MaterialPageRoute(builder: (context) => SecondPage()));
            },
        ),
      ),
    );
  }
}import 'package:flutter/material.dart';
 
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