addAndGet method
Creates a new controller that is Sync to any existing ones.
Implementation
ScrollController addAndGet() {
final initialOffset = _attachedControllers.isEmpty
? initialScrollOffset
: _attachedControllers.first.position.pixels;
final controller =
_SyncScrollController(this, initialScrollOffset: initialOffset);
_allControllers.add(controller);
controller.addListener(_offsetNotifier.notifyListeners);
return controller;
}