Helper for reading input from keyboard and gamepad. This class tracks both the current and previous state of both input devices, and implements query methods for high level input actions such as "move up through the menu" or "pause the game".
        /// <summary>
        /// Responds to user input, accepting or cancelling the message box.
        /// </summary>
        public override void HandleInput(InputState input)
        {
            PlayerIndex playerIndex;

            // We pass in our ControllingPlayer, which may either be null (to
            // accept input from any player) or a specific index. If we pass a null
            // controlling player, the InputState helper returns to us which player
            // actually provided the input. We pass that through to our Accepted and
            // Cancelled events, so they can tell which player triggered them.
            if (input.IsMenuSelect(ControllingPlayer, out playerIndex))
            {
                // Raise the accepted event, then exit the message box.
                if (Accepted != null)
                    Accepted(this, new PlayerIndexEventArgs(playerIndex));

                ExitScreen();
            }
            else if (input.IsMenuCancel(ControllingPlayer, out playerIndex))
            {
                // Raise the cancelled event, then exit the message box.
                if (Cancelled != null)
                    Cancelled(this, new PlayerIndexEventArgs(playerIndex));

                ExitScreen();
            }
        }
 /// <summary>
 /// Allows the screen to handle user input. Unlike Update, this method
 /// is only called when the screen is active, and not when some other
 /// screen has taken the focus.
 /// </summary>
 public abstract void HandleInput(InputState input);
 public override void HandleInput(InputState input)
 {
 }