custom_paint.dart

import 'package:flutter/material.dart';

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

  @override
  Widget build(BuildContext context) {
    final Size size = MediaQuery.of(context).size;

    return Scaffold(
      backgroundColor: Colors.deepPurple[100],
      appBar: AppBar(title: const Text('Custom Paint')),
      body: Stack(
        children: [
          Positioned(
            bottom: 0,
            left: 0,
            child: SizedBox(
              width: size.width,
              height: 80,
              child: Stack(
                children: [
                  CustomPaint(
                    size: Size(size.width, 80),
                    painter: BNBCustonPainter(),
                  ),
                  Center(
                    heightFactor: 0.6,
                    child: FloatingActionButton(
                      onPressed: () {},
                      backgroundColor: Colors.purple,
                      elevation: 8.0,
                      child: const Icon(Icons.shopping_basket),
                    ),
                  ),
                  SizedBox(
                    width: size.width,
                    height: 80,
                    child: Row(
                      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                      children: [
                        IconButton(
                          icon: const Icon(Icons.home),
                          color: Colors.purple,
                          onPressed: () {},
                        ),
                        IconButton(
                          icon: const Icon(Icons.restaurant_menu),
                          color: const Color(0xFFAEAEAE),
                          onPressed: () {},
                        ),
                        SizedBox(width: size.width * 0.20),
                        IconButton(
                          icon: const Icon(Icons.bookmark),
                          color: const Color(0xFFAEAEAE),
                          onPressed: () {},
                        ),
                        IconButton(
                          icon: const Icon(Icons.notifications),
                          color: const Color(0xFFAEAEAE),
                          onPressed: () {},
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class BNBCustonPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.white
      ..style = PaintingStyle.fill;
    Path path = Path()..moveTo(0, 20);
    path.quadraticBezierTo(size.width * 0.20, 0, size.width * 0.35, 0);
    path.quadraticBezierTo(size.width * 0.40, 0, size.width * 0.40, 20);
    path.arcToPoint(Offset(size.width * 0.60, 20),
        radius: const Radius.circular(10.0), clockwise: false);
    path.quadraticBezierTo(size.width * 0.60, 0, size.width * 0.65, 0);
    path.quadraticBezierTo(size.width * 0.80, 0, size.width, 20);
    path.lineTo(size.width, size.height);
    path.lineTo(0, size.height);
    path.close();
    canvas.drawShadow(path, Colors.black, 8, true);
    canvas.drawPath(path, paint);
  }

  @override
  bool shouldRepaint(BNBCustonPainter oldDelegate) => false;

  @override
  bool shouldRebuildSemantics(BNBCustonPainter oldDelegate) => false;
}