Generate flutter material color swatch code from a color

main.dart

import 'package:flutter/material.dart';

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

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String _color = '0xffffcc00';
  late final controller = TextEditingController(text: _color);

  @override
  Widget build(BuildContext context) {
    final colorHex = _color.replaceFirst('0x', '').replaceFirst('0X', '');
    late final color = Color(int.parse(colorHex, radix: 16));
    final validColor = int.tryParse(colorHex, radix: 16) != null;

    return MaterialApp(
      home: Scaffold(
        body: Container(
          constraints: const BoxConstraints(maxWidth: 400),
          padding: const EdgeInsets.all(24.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              TextField(
                controller: controller,
                onChanged: (value) => setState(() {
                  _color = value;
                }),
              ),
              if (!validColor) const Text('Invalid color'),
              if (validColor) SelectableText('''
MaterialColor($_color, {
  50: ${color.shade50},
  100: ${color.shade100},
  200: ${color.shade200},
  300: ${color.shade300},
  400: ${color.shade400},
  500: ${color.shade500},
  600: ${color.shade600},
  700: ${color.shade700},
  800: ${color.shade800},
  900: ${color.shade900},
})
                  '''),
            ],
          ),
        ),
      ),
    );
  }
}

/// credits go to @fldnascimento
/// https://github.com/fldnascimento/color_shade/blob/main/lib/src/shade.dart
abstract class Shade {
  /// Convert int to ARBG
  static String hexFromArgb(int a, int r, int g, int b) {
    return '${a.toRadixString(16).padLeft(2, '0').toUpperCase()}'
        '${r.toRadixString(16).padLeft(2, '0').toUpperCase()}'
        '${g.toRadixString(16).padLeft(2, '0').toUpperCase()}'
        '${b.toRadixString(16).padLeft(2, '0').toUpperCase()}';
  }

  /// Convert hex to int
  static int intFromHex(String hex) {
    return int.tryParse(hex, radix: 16) ?? 0;
  }

  /// Mix colors from an amount
  static Color mixColors(Color argb1, Color argb2, double amount) {
    final p = amount / 100;

    final r = ((argb2.red - argb1.red) * p + argb1.red).floor();
    final g = ((argb2.green - argb1.green) * p + argb1.green).floor();
    final b = ((argb2.blue - argb1.blue) * p + argb1.blue).floor();
    final a = ((argb2.alpha - argb1.alpha) * p + argb1.alpha).floor();

    final hex = hexFromArgb(a, r, g, b);
    return Color(intFromHex(hex));
  }

  /// Multiply the two colors
  static Color multiply(Color argb1, Color argb2) {
    final a = argb1.alpha;
    final r = (argb1.red * argb2.red / 255).floor();
    final g = (argb1.green * argb2.green / 255).floor();
    final b = (argb1.blue * argb2.blue / 255).floor();

    final hex = hexFromArgb(a, r, g, b);
    return Color(intFromHex(hex));
  }

  /// Generate shades based on colorBase
  static MaterialColor swatch(Color colorBase) {
    const baseLight = Color(0xFFFFFFFF);
    final baseDark = multiply(colorBase, colorBase);

    return MaterialColor(
      colorBase.value,
      <int, Color>{
        50: mixColors(baseLight, colorBase, 12),
        100: mixColors(baseLight, colorBase, 30),
        200: mixColors(baseLight, colorBase, 50),
        300: mixColors(baseLight, colorBase, 70),
        400: mixColors(baseLight, colorBase, 85),
        500: colorBase,
        600: mixColors(baseDark, colorBase, 87),
        700: mixColors(baseDark, colorBase, 70),
        800: mixColors(baseDark, colorBase, 54),
        900: mixColors(baseDark, colorBase, 25),
      },
    );
  }
}

/// Extends the Color class to generate shades
extension ColorShadeExtension on Color {
  MaterialColor get swatch {
    return Shade.swatch(this);
  }

  Color get shade50 => swatch[50]!;
  Color get shade100 => swatch[100]!;
  Color get shade200 => swatch[200]!;
  Color get shade300 => swatch[300]!;
  Color get shade400 => swatch[400]!;
  Color get shade500 => swatch[500]!;
  Color get shade600 => swatch[600]!;
  Color get shade700 => swatch[700]!;
  Color get shade800 => swatch[800]!;
  Color get shade900 => swatch[900]!;
}

https://dartpad.dev/?id=35a8e3858c3bdaa6864965b824bc91d9

thanks to @fldnascimento for code responsible for generating shades