keyboardWillShow gets called for other app's keyboards

I suggest you to check if your textField is first responder in keyboardWillShown method. If it is not, just ignore the notification.

func keyboardWillShow(notification: NSNotification) {
    if !myTextField.isFirstResponder() {
        return
    }
    self.keyboardIsShowing = true
    if let info = notification.userInfo {
       self.keyboardFrame = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue()
       self.arrangeViewOffsetFromKeyboard()
    }
}

UPDATE: Instead of checking for the firstResponder, it is safer if you check UIApplication.shareApplication().applicationSate == .Active

iOS 9+ only:

NSNotification that comes from keyboard contains following:

UIKeyboardIsLocalUserInfoKey - The key for an NSNumber object containing a Boolean that identifies whether the keyboard belongs to the current app.

In my case i also do this (which is probably needed for OP too):

func textFieldShouldEndEditing(_ textField: UITextField) -> Bool {
    return UIApplication.shared.applicationState == .active
}

This way keyboard won't hide when switching between applications.

Just check whether the app state is active will be fine:

- (void)handleKeyboardWillShowNotification:(NSNotification *)notifaction{
    if([UIApplication sharedApplication].applicationState != UIApplicationStateActive){
        return;
    }
    //your code below...
}