one way to fixed sliver app bar overlap

[a616781689]

// find sliverlist renderobject
    RenderSliver? renderSliver  = context.findAncestorRenderObjectOfType<RenderSliver>();  

// determineStuckOffset
  double determineStuckOffset() {
    double dy;

    try {
      dy = localToGlobal(Offset(0, -renderSliver.constraints.overlap), ancestor: renderSliver).dy;
    } catch (e) {
      // ignore and fall-through and return 0.0
      dy = 0.0;
    }
    return dy;
  }