Flutter简要自定义View

import 'package:flutter/material.dart';

void main() => runApp(new LogoApp());

class LogoApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Color(0xddffffff),
        body: CustomPaint(painter: MyCustomPainter()),
      ),
    );
  }
}
class MyCustomPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = new Paint();
    paint.color = Color(0xffff0000);
    canvas.drawCircle(Offset(20, 20), 15, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return false;
  }

}