ScrollController not attached to any scroll views

To set the initial position of a ScrollController, use the initialScrollOffset property:

_scrollController = ScrollController(initialScrollOffset: 50.0);

Check if the scrollController is attached to a scroll view by using its hasClients property first.

if (_scrollController.hasClients) 
    _scrollController.jumpTo(50.0);

Delaying it is not the right solution. Better to wait till the tree is done building by using

WidgetsBinding.instance
        .addPostFrameCallback((_){});

sample

WidgetsBinding.instance.addPostFrameCallback((_) {
      if(pageController.hasClients){
              pageController.animateToPage(page index, duration: Duration(milliseconds: 1), curve: Curves.easeInOut);
      }
});

@carlosx2 answer is correct but if someone wonder where to put WigetsBinding. So here it is.

@override
void initState(){
  super.initState();
  WidgetsBinding.instance.addPostFrameCallback((_){
    //write or call your logic
    //code will run when widget rendering complete
  });
}