posy = localOffset.dy- MediaQuery.of(context).padding.top - kToolbarHeight;

还需要将偏移量减少红点大小的一半在您的情况下，是否会像这样

also you need to decrease offset by half of the red dot size in your case if will something like this

  posx = localOffset.dx - 7.5;
  posy = localOffset.dy- MediaQuery.of(context).padding.top - kToolbarHeight - 7.5;