Java KeyListener不工作或被添加

我正在为我的学校编写Snake程序，除了key Listener之外，一切都运行得很好.我真的不知道问题出在哪里，因为我认为我打电话的方式是正确的.

下面是我的窗口类的代码:

package GUI;

import Entity.Apple;
import Entity.Schlange;
import Threads.Threads;
import Threads.KeyInput;

import javax.swing.*;

public class Window extends JFrame {
    public Window() {
        Spielfeld spielfeld = new Spielfeld();
        Apple apple = new Apple(0, 0, spielfeld);
        KeyInput keyInput = new KeyInput(); // This is the keyListener
        Schlange schlange = new Schlange(spielfeld, apple, keyInput);

        Threads thread = new Threads(spielfeld, apple, schlange);

        this.setTitle("Snake");
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setResizable(false);

        this.add(spielfeld);
        this.pack();

        this.addKeyListener(keyInput);
        this.setVisible(true);

        thread.startThread();
    }
}

以及来自key Listener的:

package Threads;

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

public class KeyInput implements KeyListener {
    public Queue<String> queue = new ConcurrentLinkedQueue<>();

    @Override
    public void keyTyped(KeyEvent e) {
        String moved = new String();
        System.out.println("keyTyped");

        if (e.getKeyCode() == KeyEvent.VK_W) {
            System.out.println("W gedrückt");
            moved = "up";
        } else if (e.getKeyCode() == KeyEvent.VK_A) {
            System.out.println("W gedrückt");
            moved = "left";
        } else if (e.getKeyCode() == KeyEvent.VK_S) {
            System.out.println("W gedrückt");
            moved = "down";
        } else if (e.getKeyCode() == KeyEvent.VK_D) {
            System.out.println("W gedrückt");
            moved = "right";
        }

        queue.add(moved);
    }

    @Override
    public void keyPressed(KeyEvent e) {
        System.out.println("keyTyped");
    }

    @Override
    public void keyReleased(KeyEvent e) {
        System.out.println("keyTyped");
    }
}

Key Listener应该被添加到窗口中，然后被赋予"Schlange"(Germ.:Snake)，在那里它将被处理.

我有很多System.out.println()代码行要调试，但它们都没有给出任何结果，我点击什么都无关紧要.

我是否应该将其添加到JPanel中？

编辑:我试着把它添加到JPanel"Spielfeld"中，很管用