import 'package:flutter/material.dart';

void main() {
  runApp(const MainApp());
}

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: Scaffold(
          body: Center(
            child: Text('hello'),
          ),
          bottomNavigationBar: CustomAppBar()),
    );
  }
}

class CustomAppBar extends StatelessWidget {
  const CustomAppBar({
    Key? key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const SizedBox(
      height: 60,
      child: BottomAppBar(
        color: Colors.green,
        child: SizedBox.expand(
          child: DecoratedBox(
            decoration: BoxDecoration(
              gradient: RadialGradient(
                colors: [
                  Colors.blue,
                  Colors.red,
                ],
                focalRadius: 3,
                focal: Alignment(0, 0.8),
                center: Alignment.topCenter,
              ),
            ),
          ),
        ),
      ),
    );
  }
}