             return _selectedViewController
         }
         set {
-            _selectedViewController = newValue
+            if let contentController = newValue as? ScrollBarContentableController {
+                scrollBar.selectedItem = contentController.item
+                _selectedViewController = newValue
+            }
         }
     }
 


public protocol ScrollBarController : ScrollBarDelegate {
    var scrollBar: ScrollBar! { get }
    var selectedViewController: UIViewController! { get set }
    var _selectedViewController: UIViewController! { get set }
    weak var delegate: ScrollBarControllerDelegate? { get set }
    var isTransitioningFromViewController: Bool { get set }

                    duration: NSTimeInterval(0), options: UIViewAnimationOptions(rawValue: 0),
                    animations: { [unowned self] (finished) -> Void in
                        //toViewController の viewWillAppear の実行が終わったあとに実行する
                        self.selectedViewController = didSelectController!
                        
                        if self.delegate != nil {
