如何比其他方法同时运行KeyListener？

Question

I'm actually coding pacman for a project, but I've encountered an issue, when I've added this part :

@Override
public void keyPressed(KeyEvent e){
    dir=e.getKeyCode();         
}

The program doesn't call that specific method that I need in order to get the right direction and then put it in the update one.

Here is the full code which I'm still working on :

import java.awt.Graphics;
import org.game.engine.Game;
import java.awt.Graphics2D;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import org.game.engine.GameApplication;

public class Pacman extends Game  {
BufferedImage pacman;
int frame;
int dir;
int x,y;
final int STEP=2;

public static void main (String[] args){
    GameApplication.start(new Pacman());
}

public Pacman(){
    title="Pacman";
    width=height=500;
    dir=KeyEvent.VK_RIGHT;
    x=300;
    y=200;
    try {
        pacman = ImageIO.read(new File("pacman.png"));
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void keyPressed(KeyEvent e){
    dir=e.getKeyCode();                
}

@Override
public void update() {
    frame++;
    if(frame>2){
        frame=0;
    }
    **switch(dir){
        case KeyEvent.VK_LEFT:
            x-=STEP;
            break;
        case KeyEvent.VK_RIGHT:
            x+=STEP;
            break;**
    }

    if(x<0){
        x=0;
    }
    else if(x> width -28-15){
        x= width-28-15;
    }

}

@Override
public void draw(Graphics g) {
    g.drawImage(pacman.getSubimage(frame*30,0,28,28),x,y,null);
}

@Override
public void init() {
}

}

EXTRA Details : So basically in order to run the project I've a game engine that helps me to process the shape of the game. In order to do that I have 4 classes :

1/ Game Application :

package org.game.engine;

import javax.swing.JFrame;

public class GameApplication {
static public void start (Game jeu) {
    JFrame fenetre=new JFrame(jeu.getTitle());
    fenetre.setSize(jeu.getWidth(),jeu.getHeight());
    fenetre.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    GameCanvas canvas=new GameCanvas(jeu);
    fenetre.add(canvas);
    fenetre.setVisible(true);
    GameLoop loop= new GameLoop(jeu,canvas);
    loop.start();
 }
}

2/ GameCanvas

package org.game.engine;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener; 
import javax.swing.JComponent;

public class GameCanvas extends JComponent{
private final Game game;

public GameCanvas(Game game) {
    this.game=game;
    **addKeyListener(this.game);** 
    requestFocus();
}
@Override
public void paintComponent(Graphics g){
    game.draw(g);
}

}

3/ Game Loop

package org.game.engine;
public class GameLoop extends Thread {
   private final Game game;
   private final GameCanvas canvas;

  public GameLoop(Game game, GameCanvas canvas) {
    this.game=game;
    this.canvas=canvas; 
  }

@Override
public void run() {
    game.init();
    while(!game.isOver()){
        game.update();
        canvas.repaint();
        try {
            Thread.sleep(game.getDelay());
        } catch (InterruptedException e) {
        }
     }
  }
 }

And finally the game itself :

4/ Game

package org.game.engine;
import java.awt.Graphics;
**import java.awt.event.KeyEvent;
 import java.awt.event.KeyListener;**

public abstract class Game **implements KeyListener**{
protected boolean over;
protected int delay=50;
protected int width=500;
protected int height=500;
protected String title="Mon jeu";

abstract public void update();
abstract public void draw(Graphics g);
abstract public void init();

public int getWidth(){ return width;}
public int getHeight(){return height;}
public String getTitle(){return title;}

public boolean isOver(){ return over;}
public long getDelay(){ return delay;}

**public void keyTyped(KeyEvent e){}
public void keyPressed(KeyEvent e){}
public void keyReleased(KeyEvent e){}**
}

The 1/ Game Application is for the execution part of the process (layout display etc..) The 2/ Game Canvas is there in order to draw the content of the window, besides it also calls the Keylistener by : addKeyListener(this.game); The 3/ Game Loop contains the main loop of the programm in the run method And finally the 4/ Game contains all the basic parametres of the programm such as the title the size and it also implements the Keylisteners.

Answer 1

For key press to be handled correctly you need to do following:

• Register the key listener/ key adapter to Swing (or AWT).
• After key pressed event is called call the method that should respond to the key.

May be you are doing these right. If so you need to narrow down the problem further for getting reasonable help.

Answer 2

You're storing the key value in a and then checking dir in your switch. Obviously this will not work. You do not seem to use a anywhere else in the application so I suggest you remove the variable completely to avoid confusion.