custom_thumb_shape.dart

import 'package:flutter/material.dart';


class CustomThumbShape extends SliderComponentShape {

  final double thumbRadius;

  const CustomThumbShape({
    required this.thumbRadius,
  });

  @override
  Size getPreferredSize(bool isEnabled, bool isDiscrete) {
    return Size.fromRadius(thumbRadius);
  }

  @override
  void paint(PaintingContext context, Offset center, {required Animation<double> activationAnimation, required Animation<double> enableAnimation, required bool isDiscrete, required TextPainter labelPainter, required RenderBox parentBox, required SliderThemeData sliderTheme, required TextDirection textDirection, required double value, required double textScaleFactor, required Size sizeWithOverflow}) {
    final canvas = context.canvas;

    final fillPaint = Paint()
      ..color = Colors.white
      ..style = PaintingStyle.fill;

    final borderPaint = Paint()
      ..color = Colors.blue
      ..strokeWidth = 3
      ..style = PaintingStyle.stroke;

    canvas..drawCircle(center, thumbRadius, fillPaint)
      ..drawCircle(center, thumbRadius, borderPaint);
  }

}