javakeylistener

Java KeyListener not working or being added

I am programming snake for my school and everything works totally fine, except for the keyListener. I don't really know where the problem is, because I think that I called the right way.

Here is the code of my window class:

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();
    }
}

And from the keyListener:

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");
    }
}

The keyListener is supposed to be added to the window, and then be given to "Schlange" (Germ.: Snake), where it will be proced.

I have a lot of lines with System.out.println() to debug, but none of them gave out anything and it doesn't matter what I click.

Should I like add it in the JPanel?

Edit: I tried adding it to the JPanel "Spielfeld", which worked

Solution

  • Three points I can hint at:

    Problem #1:

    Do NOT write the same message to sysout for different events, this will confuse you, so instead, for each method write its real name and add the parameter:

    This way you will see WHAT is triggered WHERE.

    This is mainly important, because certain keys will not trigger all 3 events (pressed, released, typed).

    Problem #2:

    If you do NOT add the panel spielfeld, the evets will in fact all get triggered. As I cannot see what your Spielfeld class is, I bet it catches ('consumes') those events.

    Quick fix: instead of adding the keylistener to this (this.addKeyListener(keyInput);), better add them to spielfeld: spielfeld.addKeyListener(keyInput);, maybe that works then.

    (And please, next time, provide ALL relevant code)

    Problem #3:

    Actually, a bunch of small problems: You did not describe your actual problem. Do the events not get triggered at all? What output messages do you get? Maybe there's a swallowed Exception somewhere that is relevant to this problem. Include a runnable example with ALL relevant classes. Usually when dumbing down the problem, you see the solution yourself.

    So, I hope this already helped. In any way, please update your question, so if future generations come here looking for the same problem, they'll have better info.