问如何在Flutter的文本输入字段中配置自动大小写行为？

EN

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
      theme: new ThemeData.dark(),
      home: new MainScreen()
  ));
}

class MainScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
            leading: new IconButton(
                icon: new Icon(Icons.menu),
                tooltip: 'Navigation menu',
                onPressed: null,
            ),
            title: new Text('Test'),
        ),
        body: new NewTest(),
    );
  }
}

/// Widget
class NewTest extends StatefulWidget {
  @override
  _NewTestInputState createState() => new _NewTestInputState();
}
/// State
class _NewTestInputState extends State<NewTest> {
  InputValue _currentInput;

  void _handleInputChange(InputValue input) {
    if (input != _currentInput){
      setState(() {
        _currentInput = input;
      });
    }
  }

  void _handleInputSubmitted(InputValue input) {
    setState(() {
      _currentInput = const InputValue();
    });
  }

  @override
  Widget build(BuildContext context) {
    InputField _widget = new InputField(
        value: _currentInput,
        hintText: 'Enter text',
        keyboardType: TextInputType.text,
        autofocus: true,
        onChanged: _handleInputChange,
        onSubmitted: _handleInputSubmitted,
        style: new TextStyle(fontSize: 20.0),
    );
    Container _container = new Container(
        child: _widget,
        decoration: new BoxDecoration(
            border: new Border.all(
                color: Colors.green[300],
                width: 2.0,
            ),
        ),
        padding: new EdgeInsets.all(16.0),
    );
    return _container;
  }
}