How can I adjust a values as page scrolls in flutter

Question

I have created a listview with a scroll controller, I am able to get offset values via _scrollController.offset now I want to be able to move from

  double initialPointX = 0.5;
  double initialPointY = 0.0;
  double hDrag = 20;
  double vDrag = -20;

to here

  double initialPointX = 0.0;
  double initialPointY = 0.0;
  double hDrag = 0.0;
  double vDrag = 0.0;

while scrolling down and back to the first values while scrolling back up.

I hope to get ideas and answers.

for context: I am trying to animate an object while scrolling to and from.