flutter:如何在文本字段中显示货币数字

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Currency Formatter'),
        ),
        body: Center(
          child: CurrencyTextField(),
        ),
      ),
    );
  }
}

class CurrencyTextField extends StatefulWidget {
  @override
  _CurrencyTextFieldState createState() => _CurrencyTextFieldState();
}

class _CurrencyTextFieldState extends State<CurrencyTextField> {
  final TextEditingController _controller = TextEditingController();
  String _formattedValue = '';

  @override
  Widget build(BuildContext context) {
    return TextField(
      controller: _controller,
      decoration: InputDecoration(
        labelText: 'Enter amount',
        suffixText: 'USD',
        suffixStyle: TextStyle(color: Colors.grey),
      ),
      onChanged: (value) {
        setState(() {
          _formattedValue = formatCurrency(value);
        });
      },
      onTap: () {
        FocusScope.of(context).requestFocus(FocusNode());
      },
    );
  }

  String formatCurrency(String value) {
    if (value == '') return '';
    final number = num.parse(value);
    final formatter = NumberFormat.simpleCurrency(symbol: 'USD');
    return formatter.format(number);
  }
}