文本字段中的flutter格式货币

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(
      home: Scaffold(
        appBar: AppBar(title: Text('Currency Formatter')),
        body: Center(
          child: CurrencyFormatterExample(),
        ),
      ),
    );
  }
}

class CurrencyFormatterExample extends StatefulWidget {
  @override
  _CurrencyFormatterExampleState createState() => _CurrencyFormatterExampleState();
}

class _CurrencyFormatterExampleState extends State<CurrencyFormatterExample> {
  final TextEditingController _controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      controller: _controller,
      keyboardType: TextInputType.number,
      inputFormatters: [
        FilteringTextInputFormatter.digitsOnly,
        CurrencyFormatter(),
      ],
      decoration: InputDecoration(
        labelText: 'Amount',
        border: OutlineInputBorder(),
      ),
    );
  }
}

class CurrencyFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue,
    TextEditingValue newValue,
  ) {
    final int newTextLength = newValue.text.length;
    if (newTextLength == 0) {
      return newValue;
    }

    String text = newValue.text.replaceAll(RegExp(r'\D'), '');
    if (text.isEmpty) {
      return newValue;
    }

    text = text.replaceAll(RegExp(r'(\d)(?=(\d{3})+(?!\d))'), r'\$1,');
    text = '\$${text}';

    return TextEditingValue(text: text);
  }
}