key未释放时调用keyReleased

Question

我正在浏览如何创建太空飞船游戏的教程。我试图控制船射击导弹的速度。现在，当我按住空格按钮时，它会快速射击，因为keyPressed方法不断被调用。我有一个如下所示的keyboardInput类：

package com.game.src.main;

import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

public class KeyInput extends KeyAdapter {
    Game game;

    public KeyInput(Game game) {
        this.game = game;
    }

    public void keyPressed(KeyEvent e) {
        game.keyPressed(e);
    }

    public void keyReleased(KeyEvent e) {
        game.keyReleased(e);
    }
}

如您所见，然后将关键事件传递给Game实例的方法。我已经设置了一个名为is_shooting的布尔值并将其设置为false。然后当按下spacekey时，它将检查is_shooting是否为false，如果是，则将其设置为true并制作导弹。当它被释放时，is_shooting会变回false。我在init（）方法中创建了一个addkeyListener，这是线程开始运行时调用的第一个函数。我在我的游戏课上：

编辑添加了我的Game类的全部代码。

    package com.game.src.main;

import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.io.IOException;

import javax.swing.JFrame;

public class Game extends Canvas implements Runnable  {

     /**
     * 
     */
    private static final long serialVersionUID = 1L;
    public static final int WIDTH = 320;
     public static final int HEIGHT = WIDTH / 12 * 9;
     public static final int SCALE = 2;
     public final String TITLE = "2D Space Game";

     private boolean running = false ;
     private Thread thread; 


     private BufferedImage spriteSheet = null;
     private BufferedImage background = null;

     private boolean is_shooting = false;

     private Player p;
     private Controller c;


     public  void init(){
        BufferedImageLoader loader = new BufferedImageLoader();

        try{
            spriteSheet = loader.loadImage("/sprite_sheet.png");
            background = loader.loadImage("/background.png");
        }catch(IOException e){
            e.printStackTrace();
        }
        addKeyListener(new KeyInput(this));
            p = new Player(200,200,this);
            c = new Controller(this);


     }

     private synchronized void start(){
        if (running)
            return;

        running = true;
        thread = new Thread(this);
        thread.start();
     }

     private synchronized void stop(){
         if (!running)
             return;
         running = false;
         try{
             thread.join();
         }catch (InterruptedException e) {
             e.printStackTrace();
         }
         System.exit(1);
     }

     public void run(){
        init();
         long lastTime = System.nanoTime();
         final double amountOfTicks = 60.0;
         double ns = 1000000000/ amountOfTicks;

         double delta = 0;
         int updates = 0;
         int frames = 0;
         long timer = System.currentTimeMillis();
         while (running){
             // this would be the game loop
         long now = System.nanoTime();

         delta += (now - lastTime) / ns; 
         lastTime = now;
         if(delta >= 1 ){
             tick();
             updates++;
             delta--;
         }
         render();
         frames++;

         if(System.currentTimeMillis() - timer > 1000){
            timer += 1000;
            System.out.println(updates + "Ticks, FPS"+ frames);
            updates = 0 ;
            frames = 0;
         }
        }
         stop();
     }

     private void tick(){
         p.tick();
         c.tick();
     }

     private void render(){

         BufferStrategy bs = this.getBufferStrategy();
         if (bs ==null){
             createBufferStrategy(3);
             return;
         }
         Graphics g = bs.getDrawGraphics();

         g.drawImage(background,0,0,null);
         p.render(g);
         c.render(g);


         g.dispose();
         bs.show();

     }

public void keyPressed(KeyEvent e){
    int key = e.getKeyCode();

    if (key == KeyEvent.VK_RIGHT){
        p.setVelX(5);
    }
    else if (key == KeyEvent.VK_LEFT){
        p.setVelX(-5);
    }
    else if (key == KeyEvent.VK_DOWN){
        p.setVelY( 5);
    }
    else if (key == KeyEvent.VK_UP){
        p.setVelY(- 5);
    }
    else if (key == KeyEvent.VK_SPACE && !is_shooting)
    {

        is_shooting = true;

        c.addBullet(new Bullet(p.getX(), p.getY(),this));

    }
}
public void keyReleased(KeyEvent e){
int key = e.getKeyCode();

    if (key == KeyEvent.VK_RIGHT){
        p.setVelX(0);
    }
    else if (key == KeyEvent.VK_LEFT){
        p.setVelX(0);
    }
    else if (key == KeyEvent.VK_DOWN){
        p.setVelY(0);
    }
    else if (key == KeyEvent.VK_UP){
        p.setVelY(0);
        System.out.println("IM in HEREE");
    }
    else if (key == KeyEvent.VK_SPACE){
        is_shooting = false;
    }
 }
     public static void main(String args[]){
         Game game= new Game();

         game.setPreferredSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE ));
         game.setMaximumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE ));
         game.setMinimumSize(new Dimension(WIDTH * SCALE, HEIGHT * SCALE ));

         JFrame frame = new JFrame(game.TITLE);
         frame.add(game);
         frame.pack();
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setResizable(false);
         frame.setLocationRelativeTo(null);
         frame.setVisible(true);
         System.out.println(System.getProperty("user.dir"));
         game.start();
     }

     public BufferedImage getSpriteSheet(){
         return spriteSheet;
     }
}

对于一些println语句，我发现keyReleased函数被调用了我正在按下的'ANY'键。当我按下键而不释放键时，如何防止调用keyReleased方法？