Flutter spinbox sample

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



// MySpin class

class MySpin extends StatefulWidget {
  const MySpin(
      {super.key,
      required this.decimals,
      required this.increment,
      required this.value,
      required this.onChanged});

  final int decimals;
  final double increment;
  final double value;
  final Function(double) onChanged;

  @override
  State<MySpin> createState() => _MySpinState();
}

class _MySpinState extends State<MySpin> {
  late double _value = widget.value;
  late int _decimals = widget.decimals;
  late double _increment = widget.increment;
  double _iconSize = 20;
  double _textWidth = 50;
  TextEditingController _controller = TextEditingController();

  @override
  void initState() {
    _controller.text = _value.toStringAsFixed(_decimals);
    //_controller.text = _value.toStringAsFixed(_digits);

    _controller.addListener(() {
      final v = double.tryParse(_controller.text) != null
          ? double.parse(_controller.text)
          : _value;
      if (v == _value) return;

      setState(() {
        _value = double.parse(_controller.text);
      });
      widget.onChanged(_value);
    });

    super.initState();
  }

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

  @override
  Widget build(BuildContext context) {
    return Container(
      decoration: BoxDecoration(
          border: Border.all(), borderRadius: BorderRadius.circular(10)),
      child: IntrinsicWidth(
        child: Row(children: [
          IconButton(
              icon: Icon(Icons.remove_circle_outline),
              visualDensity: VisualDensity.compact,
              iconSize: _iconSize,
              onPressed: () {
                setState(() {
                  _value -= _increment;
                  _controller.text = _value.toStringAsFixed(_decimals);
                });
                widget.onChanged(_value);
              }),
          SizedBox(
              width: _textWidth,
              child: TextField(
                textAlign: TextAlign.center,
                keyboardType: TextInputType.number,
                controller: TextEditingController(
                    text: _value.toStringAsFixed(_decimals)),
                decoration: null,
                inputFormatters: [
                  //NumberTextInputFormatter(decimalDigits: _digits)
                ],
                onChanged: (value) {
                  TextPosition textPos = _controller.selection.base;
                  _controller.text = value;
                  _controller.selection = TextSelection.fromPosition(textPos);
                  if (double.tryParse(value) != null) {
                    setState(() {
                      _value = double.parse(value);
                    });

                    widget.onChanged(_value);
                  }
                },
              )),
          IconButton(
              visualDensity: VisualDensity.compact,
              iconSize: _iconSize,
              icon: Icon(Icons.add_circle_outline),
              onPressed: () {
                setState(() {
                  _value += _increment;
                  _controller.text = _value.toStringAsFixed(_decimals);
                });
                widget.onChanged(_value);
              }),
        ]),
      ),
    );
  }
}

// main app

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(colorSchemeSeed: Colors.blue),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({super.key, required this.title});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  double _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.title)),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('You have pushed the button this many times:'),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
            SpinBox(
              decimals: 1,
              value: _counter,
              onChanged: (value) {
                setState(() {
                  _counter = value;
                });
              },),
              MySpin(
                decimals: 1,
                increment: 0.1,
                value: _counter,
                onChanged: (value) {
                  setState(() {
                    _counter = value;
                  });
                },
              ),

          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}