tiny_stadium_button.dart

import 'package:flutter/material.dart';

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

class App extends StatelessWidget {
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark(),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: TinyStadiumButton(
            label: "Press Me!",
            foregroundColor: Color(0xffffffff),
            backgroundColor: Color(0xffee5253),
          ),
        ),
      ),
    );
  }
}

class TinyStadiumButton extends StatelessWidget {
  TinyStadiumButton({
    @required this.label,
    @required this.foregroundColor,
    @required this.backgroundColor,
    this.onTap,
    Key key,
  })  : assert(label != null),
        assert(foregroundColor != null),
        assert(backgroundColor != null),
        super(key: key);

  final String label;

  final Color foregroundColor;

  final Color backgroundColor;

  final void Function() onTap;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: onTap,
      child: Container(
        decoration: ShapeDecoration(
          shape: StadiumBorder(),
          color: backgroundColor,
        ),
        padding: EdgeInsets.symmetric(vertical: 6, horizontal: 12),
        child: Text(
          label,
          style: TextStyle(
            color: foregroundColor,
            fontWeight: FontWeight.w600,
          ),
        ),
      ),
    );
  }
}