如何动态显示TextField下的字符数(内联)

import 'package:flutter/material.dart';

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TextEditingController _controller = TextEditingController();
  int _characterCount = 0;

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("动态显示字符数"),
      ),
      body: Column(
        children: [
          TextField(
            controller: _controller,
            onChanged: (text) {
              setState(() {
                _characterCount = text.length;
              });
            },
          ),
          Text("字符数：$_characterCount"),
        ],
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyHomePage(),
  ));
}