I want to create a slider UI to manipulate opacity

Question

I would like to make such a slider. The color OK be fixed at black.

The current code is as follows

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Slider(
        activeColor: ColorManager.blueColor,
        value: _opacity,
        min: 0.0,
        max: 1.0,
        onChanged: updateOpacity,
      ),
    );
  }