如何在颤振中将数据从 TextFormField 传递到 List？

我有以下工作代码：

class Submit extends StatefulWidget {
  @override
  _SubmitState createState() => new _SubmitState();
}

class _SubmitState extends State<Submit> {
  final scaffoldKey = new GlobalKey<ScaffoldState>();
  final formKey = new GlobalKey<FormState>();
  final myController = new TextEditingController();
  double _w;

  @override
  void dispose() {
    // Clean up the controller when the Widget is removed from the Widget tree
    myController.dispose();
    super.dispose();
  }

  void _submit() {
    final form = formKey.currentState;

    if (form.validate()) {
      form.save();
      _performSubmit();
    }
  }

  void _performSubmit() {

    final double data = double.parse(myController.text)*(2);
    var route = new MaterialPageRoute(builder: (BuildContext context) =>
    new NextPage(w1: data.toStringAsFixed(3)),
    );

    Navigator.of(context).push(route);
  }

  @override
  Widget build(BuildContext context) {

    void _restart() {
      Navigator.of(context).push(new MaterialPageRoute(
          builder: (BuildContext context) => new HomePage()));
    }

    return new Scaffold(
      key: scaffoldKey,
      appBar: new AppBar(
        actions: <Widget>[
        ],
        title: new Text('Next Page'),
      ),
      body:  new Form(
          key: formKey,
          child: new Column(
            children: [
              new TextFormField(
                controller: myController,
                keyboardType: TextInputType.numberWithOptions(decimal: true),
                onSaved: (val) => _w = double.parse(val),
              ),
              new RaisedButton(
                onPressed: _submit,
                child: new Text(
                  'Next Page',
                ),
              )
            ],
          ),
        ),
    );
  }
}



class NextPage extends StatefulWidget {

  final String w1;

  NextPage({Key key, this.w1}) : super (key: key);

  @override
  _NextPageState createState() => _NextPageState();
}


class _NextPageState extends State<NextPage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
          title: new Text("Second page")
      ),
      body: new Text("${widget.w1}")
    );
  }
}

在这里，我传递了一个乘以 2 的变量（称为w1），然后在下一个屏幕 ( NextScreen) 上使用Text. 但是我想要一个 List 上的结果，它是在我接下来展示的其他类中定义的。我想显示w1文本所在的变量的值1.1（内部List<Entry>）。接下来我有完整的代码，但我不知道如何传递变量。如果我写new Entry('${widget.w1}',),我得到undefined name widget。

我怎么能把我的变量传递给那个列表？

class Submit extends StatefulWidget {
  @override
  _SubmitState createState() => new _SubmitState();
}

class _SubmitState extends State<Submit> {
  final scaffoldKey = new GlobalKey<ScaffoldState>();
  final formKey = new GlobalKey<FormState>();
  final myController = new TextEditingController();
  double _w;

  @override
  void dispose() {
    // Clean up the controller when the Widget is removed from the Widget tree
    myController.dispose();
    super.dispose();
  }

  void _submit() {
    final form = formKey.currentState;

    if (form.validate()) {
      form.save();
      _performSubmit();
    }
  }

  void _performSubmit() {

    final double data = double.parse(myController.text)*(2);
    var route = new MaterialPageRoute(builder: (BuildContext context) =>
    new NextPage(w1: data.toStringAsFixed(3)),
    );

    Navigator.of(context).push(route);
  }

  @override
  Widget build(BuildContext context) {

    void _restart() {
      Navigator.of(context).push(new MaterialPageRoute(
          builder: (BuildContext context) => new HomePage()));
    }

    return new Scaffold(
      key: scaffoldKey,
      appBar: new AppBar(
        actions: <Widget>[
        ],
        title: new Text('Next Page'),
      ),
      body:  new Form(
          key: formKey,
          child: new Column(
            children: [
              new TextFormField(
                controller: myController,
                keyboardType: TextInputType.numberWithOptions(decimal: true),
                onSaved: (val) => _w = double.parse(val),
              ),
              new RaisedButton(
                onPressed: _submit,
                child: new Text(
                  'Next Page',
                ),
              )
            ],
          ),
        ),
    );
  }
}



class NextPage extends StatefulWidget {

  final String w1;

  NextPage({Key key, this.w1}) : super (key: key);

  @override
  _NextPageState createState() => _NextPageState();
}


class _NextPageState extends State<NextPage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
          title: new Text("Second page")
      ),
      body: new ListView.builder(
        itemBuilder: (BuildContext context, int index) =>
        new EntryItem(data[index]),
        itemCount: data.length,
      ),
    );
  }
}


// One entry in the multilevel list displayed by this app.
class Entry {
  Entry(this.title, [this.children = const <Entry>[]]);

  final String title;
  final List<Entry> children;
}

// The entire multilevel list displayed by this app.

List<Entry> data = <Entry>[
  new Entry(
    'First',
    <Entry>[
      new Entry(
        '1.1',
      ),
    ],
  ),
];

// Displays one Entry. If the entry has children then it's displayed
// with an ExpansionTile.
class EntryItem extends StatelessWidget {
  const EntryItem(this.entry);

  final Entry entry;

  Widget _buildTiles(Entry root) {
    if (root.children.isEmpty)
      return new ListTile(
          title: new Text(root.title));

    return new ExpansionTile(
      key: new PageStorageKey<Entry>(root),
      title: new Text(root.title,),
      children: root.children.map(_buildTiles).toList(),
    );
  }

  @override
  Widget build(BuildContext context) {
    return _buildTiles(entry);
  }
}