         //disable autoresizing mask
         self.controllersContainer.translatesAutoresizingMaskIntoConstraints = false
         self.buttonsContainer.translatesAutoresizingMaskIntoConstraints = false
+        self.blackLine.translatesAutoresizingMaskIntoConstraints = false
         self.separatorLine.translatesAutoresizingMaskIntoConstraints = false
         
         //setup constraints

            for i in 0 ..< self.tabIcons.count {
                
                let button:UIButton = self.createButton(forIndex: i)
                
                self.buttonsContainer.addSubview(button)
                
                self.buttons[i] = button
            }
            self.setupButtonsConstraints()
        }

            self.view.addConstraints(self.verticalLayoutConstraintsForButtonAtIndex(index: i))
            self.view.addConstraint(self.widthLayoutConstraintForButtonAtIndex(index: i))
            self.view.addConstraint(self.heightLayoutConstraintForButtonAtIndex(index: i))
            
            if i == centerIndex {
//                let bounds = self.buttonsContainer.convert(button.frame, to: self.view)
                centerButtonOverlay.translatesAutoresizingMaskIntoConstraints = false
                centerButtonOverlay.topAnchor.constraint(equalTo: button.topAnchor).isActive = true
                centerButtonOverlay.bottomAnchor.constraint(equalTo: button.bottomAnchor).isActive = true
                centerButtonOverlay.leadingAnchor.constraint(equalTo: button.leadingAnchor).isActive = true
                centerButtonOverlay.trailingAnchor.constraint(equalTo: button.trailingAnchor).isActive = true
            }
        }
    }
    
