Getting screen size in a class without buildcontext in Flutter

I am trying to get screen size in flutter inside a custom class which donot have build method in it. How can i get screen size without using buildcontext class?

The following code :

class ShapesPainter extends CustomPainter {
  @override
  void paint(Canvas canvas, Size size) {

    BuildContext context;
    double width = MediaQuery.of(context).size.width;
    double height = MediaQuery.of(context).size.height;
    final paint = Paint();

    paint.color = Colors.deepOrange;

    var center = Offset(size.width / 2, size.height / 2);

    print(height);
    print(width);

    Rect rect = Rect.fromLTWH(0.0, 0.0, width, height);
    canvas.drawRect(rect, paint);
  }

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

gives following error :

The following assertion was thrown during paint(): 'package:flutter/src/widgets/media_query.dart': Failed assertion: line 689 pos 12: 'context != null': is not true.

use

MediaQueryData.fromWindow(WidgetsBinding.instance.window);

you can use it to get MediaQuery without need context it depend on instance of window to get size information