selectable_button.dart

import 'package:flutter/material.dart';

class SelectableButton extends StatefulWidget {
  SelectableButton({
    super.key,
    required this.selected,
    this.style,
    required this.onPressed,
    required this.child,
  });

  final bool selected;
  final ButtonStyle? style;
  final VoidCallback? onPressed;
  final Widget child;

  bool get enabled => onPressed != null;

  @override
  State<SelectableButton> createState() => _SelectableButtonState();

}

class _SelectableButtonState extends State<SelectableButton> {
  late final MaterialStatesController statesController;

  void initState() {
    super.initState();
    statesController = MaterialStatesController({
      if (widget.selected) MaterialState.selected
    });
  }

  @override
  void didUpdateWidget(SelectableButton oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.selected != oldWidget.selected) {
      statesController.update(MaterialState.selected, widget.selected);
    }
  }

  @override
  Widget build(BuildContext context) {
    return TextButton(
      statesController: statesController,
      style: widget.style,
      onPressed: widget.onPressed,
      child: widget.child,
    );
  }
}

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

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  bool selected = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: SelectableButton(
          selected: selected,
          style: ButtonStyle(
            foregroundColor: MaterialStateProperty.resolveWith<Color?>(
              (Set<MaterialState> states) {
                if (states.contains(MaterialState.selected)) {
                  return Colors.white;
                }
                return null; // defer to the defaults
              },
            ),
            backgroundColor: MaterialStateProperty.resolveWith<Color?>(
              (Set<MaterialState> states) {
                if (states.contains(MaterialState.selected)) {
                  return Colors.indigo;
                }
                return null; // defer to the defaults
              },
            ),
          ),
          onPressed: () {
            setState(() { selected = !selected; });
          },
          child: Text('toggle selected'),
        ),
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(home: Home()));
}