import 'package:flutter/material.dart';

class BgPainter extends CustomPainter {

  final double bezierHeight;
  final Color bgColor ;

  BgPainter({
      this.bezierHeight = 10,
      this.bgColor = Colors.white,
  });

  @override
  void paint(Canvas canvas, Size size) {

    Path path = Path();
    //移动到点 P0点 也是曲线的起点
    path.lineTo(0, 0);
    path.lineTo(size.width, 0);
    path.lineTo(size.width, size.height - bezierHeight);
    path.quadraticBezierTo(size.width / 2.0, size.height, 0, size.height - bezierHeight);
    path.close();

    Paint paint = Paint()
      ..color = bgColor
      ..style = PaintingStyle.fill;

    canvas.drawPath(path, paint);

  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) => false;

}