KeyListener deja de funcionar

[Neoff224]

Código:

import java.awt.BorderLayout;
import javax.swing.JPanel;
import java.awt.*;
import java.awt.event.*;
import java.awt.Toolkit;
import java.awt.Image;
import java.awt.event.MouseEvent;
import java.awt.event.ActionEvent;
import java.awt.event.MouseListener;
import javax.swing.*; 
import java.net.URL;

public class RType extends JFrame
{
    private JPanel menuInicial;
    
    public RType() {
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        muestraMenu();
    }
    
    public void muestraMenu()
    {
        menuInicial = new MenuInicial();
        this.add(menuInicial, BorderLayout.CENTER);
        this.pack();
        this.setSize(550, 550);
        this.setResizable(false);
        this.setLocationRelativeTo(null);
        this.setVisible(true);
    }
    
    public static void main(String [] args)
    {
        RType gameInstance = new RType();
    }
}