 
     var conversationCollectionViewHasBeenMovedToBottomOnce = false
 
-
     // Keyboard 动画相关
     var conversationCollectionViewContentOffsetBeforeKeyboardWillShow = CGPointZero
     var conversationCollectionViewContentOffsetBeforeKeyboardWillHide = CGPointZero
-    //var messageToolbarBottomConstraintConstantAfterKeyboardWillShow: CGFloat = 0
     var isKeyboardVisible = false
     var keyboardHeight: CGFloat = 0
-    //var firstTime = true
 
     var keyboardShowTimes = 0 {
         willSet {

    // MARK: Keyboard

    func handleKeyboardWillShowNotification(notification: NSNotification) {
        println("showKeyboard")

        keyboardShowTimes += 1


            let keyboardEndFrame = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue()
            let keyboardHeight = keyboardEndFrame.height

            self.keyboardHeight = keyboardHeight

            UIView.animateWithDuration(animationDuration, delay: 0, options: UIViewAnimationOptions(animationCurveValue << 16), animations: { () -> Void in
                self.messageToolbarBottomConstraint.constant = keyboardHeight
                self.view.layoutIfNeeded()
