flutter で route による画面切替ができないのはなぜか

flutter で　画面切替の処理をするのに、参考例とかを見て簡単なのを作ったが、この書き方では画面が切り替わらない。どこの書き方が間違っているのか？
主画面で　Test Input に文字『q』を入れると、navigator.pushName が動くようにしているが、これではだめなのか？

import 'package:flutter/material.dart';
//import "package:intl/intl.dart"; // (DateFormat('MM/dd/yyyy HH:mm:ss::SS')　に必要
import 'package:flutter/services.dart' show rootBundle;

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'RoutesTest',
      //home: MyInit(),
      initialRoute: '/',
    routes: {
    '/': (context) => MyApp_Pejv(),
    '/second': (context) => MyInit(),
    },
    );
  }
}

class MyInit extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Init',
      home: MyInitForm(),
    );
  }
}

// Define a custom Form widget.
class MyInitForm extends StatefulWidget {
  @override
  _MyInitFormState createState() => _MyInitFormState();
}

class _MyInitFormState extends State<MyInitForm> {

  @override
  Widget build(BuildContext context) {
    final searchText = new Flexible(
      child: TextField(
        //controller: myInitController,
      ),
    );
    return Scaffold(
      appBar: AppBar(
        title: Text("init_set"),
        leading: BackButton(
          color: Colors.white,
        )
       ),
      body: Center(child: Text("exam: font_set")),

      floatingActionButton: FloatingActionButton(
          child: Icon(Icons.android),
          onPressed: () => Navigator.pushNamed(
            context,
            '/',
          ),
      ),
    );
  }
}

class MyApp_Pejv extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'test',
      home: MyPejvForm(),
    );
  }
}

class MyPejvForm extends StatefulWidget {
  @override
  _MyPejvFormState createState() => _MyPejvFormState();
}

class _MyPejvFormState extends State<MyPejvForm> {
  final myController = TextEditingController();
  @override
  void dispose() {
    // Clean up the controller when the widget is disposed.
    myController.dispose();
    super.dispose();
  }
  @override
  Widget build(BuildContext context) {
    final searchText = new Flexible(
      child: TextField(
        controller: myController,
        onChanged: (String vorto) {
          if (vorto == "q") {
            print("changed ini vorto=" + vorto + "==");
            Navigator.pushNamed(
              context,
              '/second',
            );
          }
        },
      ),
    );
    return Scaffold(

      appBar: AppBar(
        title: Row(mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: [
          Text(" Test Input:"),
          SizedBox(width: 5),
          searchText,
        ]),
      ),
      body: Text("Input"),
    );
  }
}