override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        // btn
        loginBtn.layer.cornerRadius = 3
        
        // text
        userText.delegate = self
        passwordText.delegate = self
        
        
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ViewController.keyboardWillShow(_:)), name: UIKeyboardWillShowNotification, object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ViewController.keyboardWillHide(_:)), name: UIKeyboardWillHideNotification, object: nil)

    }

 func keyboardWillShow(notification: NSNotification) {
        if isMovied {
            return
        }
        isMovied = true
        if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
            
            UIView.animateWithDuration(0.25, animations: {
                self.view.frame.origin.y -= keyboardSize.height
                }
            )
        }
        
    }
    
    func keyboardWillHide(notification: NSNotification) {
        
        isMovied = false
        if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.CGRectValue() {
            UIView.animateWithDuration(0.25, animations: {
                self.view.frame.origin.y += keyboardSize.height
            })
        }
    }