Flutter CircleProgressBarPainter

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

class CustomViewPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => CustomViewPageState();
}

class CustomViewPageState extends State<CustomViewPage>
    with SingleTickerProviderStateMixin {
  Animation<double> _doubleAnimation;
  AnimationController _controller;
  CurvedAnimation curvedAnimation;

  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: Duration(seconds: 2));
    curvedAnimation =
        CurvedAnimation(parent: _controller, curve: Curves.decelerate);
    _doubleAnimation = Tween(begin: 0.0, end: 360.0).animate(_controller);

    _controller.addListener(() {
      if(mounted){
        this.setState(() {});
      }
    });
    onAnimationStart();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
        width: 100.0,
        height: 100.0,
        margin: EdgeInsets.all(8.0),
        child: CustomPaint(
            child: Center(
                child: Text((_doubleAnimation.value / 3.6).round().toString())),
            painter: CircleProgressBarPainter(_doubleAnimation.value)
        ),
      );
  }

  void onAnimationStart() {
    _controller.forward(from: 0.0);
  }

  @override
  void reassemble() {
    super.reassemble();
    onAnimationStart();
  }

  @override
  void dispose() {
    super.dispose();
    _controller.dispose();
  }
}

class CircleProgressBarPainter extends CustomPainter {
  Paint _paintBackground;
  Paint _paintFore;
  final double pi = 3.1415926;
  var jindu;

  CircleProgressBarPainter(this.jindu) {
    _paintBackground = Paint()
      ..color = Colors.grey
      ..strokeCap = StrokeCap.round
      ..style = PaintingStyle.stroke
      ..strokeWidth = 10.0
      ..isAntiAlias = true;
    _paintFore = Paint()
      ..color = Colors.red
      ..strokeCap = StrokeCap.round
      ..style = PaintingStyle.stroke
      ..strokeWidth = 10.0
      ..isAntiAlias = true;
  }
  @override
  void paint(Canvas canvas, Size size) {
    canvas.drawCircle(Offset(size.width / 2, size.height / 2), size.width / 2,_paintBackground);
    Rect rect = Rect.fromCircle(
      center: Offset(size.width / 2, size.height / 2),
      radius: size.width / 2,
    );
    canvas.drawArc(rect, 0.0, jindu * 3.14 / 180, false, _paintFore);
  }

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