I was using a ScrollBar with a ListView widget and was getting this error in the debug console. To get rid of it, I had to set the ScrollController on both widgets. final yourScrollController = ScrollController(); Scrollbar( isAlwaysShown: true, thickness: 10, controller: yourScrollController, // Here child: ListView.builder( padding: EdgeInsets.zero, scrollDirection: Axis.vertical, controller: yourScrollController, // AND … Read more