flutter-sport/lib/widgets/popmenu_bg.dart

import 'dart:ui';

import 'package:flutter/material.dart';
import 'package:flutter/painting.dart';

class PopmenuShape extends ShapeBorder{

  final double borderWidth;
  final BorderRadius borderRadius;

  const PopmenuShape({
    this.borderWidth: 1.0,this.borderRadius: BorderRadius.zero,})
      : assert(borderRadius != null);

  @override
  EdgeInsetsGeometry get dimensions {
    return new EdgeInsets.all(borderWidth);
  }

  @override
  ShapeBorder scale(double t) {
    return PopmenuShape(
      borderWidth: borderWidth * (t),borderRadius: borderRadius * (t),);
  }

  @override
  Path getInnerPath(Rect rect,{ TextDirection textDirection }) {
    return new Path()
      ..addRRect(borderRadius.resolve(textDirection).toRRect(rect).deflate(
          borderWidth));
  }

  @override
  Path getOuterPath(Rect rect,{ TextDirection textDirection }) {
    return new Path()
      ..addRRect(borderRadius.resolve(textDirection).toRRect(rect));
  }

  @override
  void paint(Canvas canvas,Rect rect,{ TextDirection textDirection }) {
    rect = rect.deflate(borderWidth / 2.0);

    Paint paint;
    final RRect borderRect = borderRadius.resolve(textDirection).toRRect(rect);
    paint = new Paint()
      ..color = Colors.white
      ..style = PaintingStyle.fill
      ..strokeWidth = borderWidth;
    // canvas.drawRRect(borderRect,paint);
    Path path = Path()..moveTo(borderRect.width - 10, borderRect.top +2 )..lineTo(borderRect.width - 20, borderRect.top - 10)..lineTo(borderRect.width - 30,  borderRect.top+2);
    // canvas.drawShadow(
    //     path,
    //     Color(0xffdcdcdc),
    //     1,
    //     false);
    canvas.drawPath(path, paint);
  }
}