如何在Flutter中允许textinput.number中的空格？

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final _textController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Demo'),
      ),
      body: Padding(
        padding: EdgeInsets.all(20.0),
        child: TextField(
          controller: _textController,
          keyboardType: TextInputType.number,
          inputFormatters: [WhitelistingTextInputFormatter.digits],
          decoration: InputDecoration(
            labelText: 'Number input with spaces',
          ),
        ),
      ),
    );
  }
}