如何创建在用户输入时更改字体和颜色的TextField？

dependencies:
  flutter:
    sdk: flutter

import 'package:flutter/material.dart';

class MyTextField extends StatefulWidget {
  @override
  _MyTextFieldState createState() => _MyTextFieldState();
}

class _MyTextFieldState extends State<MyTextField> {
  String userInput = '';

  @override
  Widget build(BuildContext context) {
    return TextField(
      onChanged: (value) {
        setState(() {
          userInput = value;
        });
      },
      style: TextStyle(
        fontSize: 16.0,
        color: Colors.blue,
      ),
    );
  }
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text('Change Text Field'),
    ),
    body: Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          MyTextField(),
          Text(
            'User Input: $userInput',
            style: TextStyle(
              fontSize: 20.0,
              fontWeight: FontWeight.bold,
            ),
          ),
        ],
      ),
    ),
  );
}