Double-number-input-demo

readme.md

Double-number-input-demo

Created with <3 with dartpad.dev.

main.dart

// Demo2 for double number input
// only accepts minus sign at first position

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: MyDemo(),
    );
  }
}

class MyDemo extends StatefulWidget {
  const MyDemo({
    Key? key,
  }) : super(key: key);

  @override
  State<MyDemo> createState() => _MyDemoState();
}

class _MyDemoState extends State<MyDemo> {
  double? _myDoubleNumber;
  final RegExp _myPattern = RegExp(r'^-?[\d,.]*$');

  void _updateMyDoubleNumber(value) {
    setState(() {
      _myDoubleNumber = double.tryParse(value);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Your number is: ${_myDoubleNumber ?? "invalid number!"}"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.start,
          children: [
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 16),
              child: TextField(
                decoration: const InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'Enter a number',
                ),
                keyboardType:
                    const TextInputType.numberWithOptions(decimal: true),
                inputFormatters: [
                  TextInputFormatter.withFunction(
                    (TextEditingValue oldValue, TextEditingValue newValue) {
                      return _myPattern.hasMatch(newValue.text)
                          ? newValue
                          : oldValue;
                    },
                  ),
                ],
                onChanged: (value) => _updateMyDoubleNumber(value),
              ),
            )
          ],
        ),
      ),
    );
  }
}