在Flutter中仅显示TextField中的英文数字

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: 'TextField Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

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

class _MyHomePageState extends State<MyHomePage> {
  final RegExp _regex = RegExp(r'[a-zA-Z0-9]'); // 正则表达式，匹配英文数字字符

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('TextField Demo'),
      ),
      body: Center(
        child: Padding(
          padding: EdgeInsets.all(16.0),
          child: TextField(
            inputFormatters: [
              FilteringTextInputFormatter.allow(_regex), // 使用正则表达式过滤输入
            ],
          ),
        ),
      ),
    );
  }
}