Flutter中Canvas的绘制每一帧都需要重新生成一个CustomPainter？

在学习Flutter的Canvas的时候，数据发生改变，
重新绘制调用void paint(Canvas canvas, Size size)
我打印的log中print(" 对象 MyPaint ======= $this");，
每次执行paint所打印的this对象地址都不一样。

还是说，flutter的绘画机制就是这样。每一次重新构建Widget的时候，整个组件树都要重新new。
我使用的是provider去load的图片。

获取图片的代码

  void setPhotoModelImageAssetPath(String path) async {
    if (_photoModel == null) {
      _photoModel = PhotoModel();
    }
    if (path == _photoModel.path) {
      return;
    }else{
      print("path = $path mPath =${_photoModel.path}");
      _photoModel.path=path;
      // 设置图片
      _photoModel.image = await _loadImage(path);
      notifyListeners();
    }
  }

引用图片的位置

class Painter extends StatefulWidget {
  @override
  _PainterState createState() => _PainterState();
}

class _PainterState extends State<Painter> {
  @override
  Widget build(BuildContext context) {
    return SizedBox(
      width: double.infinity,
      height: double.infinity,
      child: Consumer<PhotoProvider>(
        builder: (context, photo, child) {
          return CustomPaint(
            painter: MyPaint(image: photo.photoModel?.image),
          );
        },
      ),
    );
  }
}

自定义的画版

class MyPaint extends CustomPainter {
  Paint _paint;
  ui.Image image;
  MyPaint({this.image}) {
    _paint = Paint();
    _paint.color = Color(0xff333333);
    _paint.strokeWidth = 5;
  }
  @override
  void paint(Canvas canvas, Size size) {
    print(" 对象  MyPaint  ======= $this");
//    print(" draw size =>>> $size");
    if (image != null) {
      print(" ========画=======");
      var rect = Rect.fromPoints(Offset.zero, size.bottomRight(Offset.zero));
      canvas.drawImage(image, Offset.zero, _paint);
    }
  }

  @override
  bool shouldRepaint(MyPaint oldDelegate) {
//    print("shouldRepaint ${this.image != oldDelegate.image}");
    return this.image != oldDelegate.image;
  }
}