Comment résoudre les problèmes VK_ et NullPointerException?

Question

import java.awt.Color; 

import java.awt.Graphics; 
import java.awt.Graphics2D; 
import java.awt.GraphicsEnvironment; 
import java.awt.Rectangle; 
import java.awt.event.KeyEvent; 
import java.awt.event.KeyListener; 
import java.awt.image.BufferedImage; 
import javax.swing.JFrame; 
import javax.swing.JOptionPane; 

/** 
* 
* @author Zeveso 
*/ 
public class gameStart extends JFrame { 

//set Global variables 
final int WIDTH = 400, HEIGHT = 400; 
//Dimension dim = Toolkit.getDefaultToolkit().getScreenSize(); 
double cOspeed = .5; //car 1 speed 
double cTspeed = .5; //car 2 speed 
Boolean winnerChosen = false; 
Boolean canLap = false; 
Boolean canLapT = false; 
int cOlaps = 0; 
int cTlaps = 0; 
final int UP = 0, RIGHT = 1, DOWN = 2, LEFT = 3; 
//direction of carOne 
int cODirection = UP; 
int cTDirection = UP; 
//setup for double buffer 
BufferedImage bufImg; 
//set Global Track 
//set outside 
Rectangle left = new Rectangle(0, 0, WIDTH/10, HEIGHT); 
Rectangle right = new Rectangle((WIDTH/10) * 9, 0, WIDTH/5, HEIGHT); 
Rectangle top = new Rectangle(0, 0, WIDTH, HEIGHT/8); 
Rectangle bottom = new Rectangle(0, (HEIGHT/15) * 14, WIDTH, HEIGHT/9); 
//set inside 
Rectangle topInr = new Rectangle((WIDTH/11) * 2, (HEIGHT/16) * 3, (WIDTH/14) * 9, HEIGHT/10); 
Rectangle bottomInr = new Rectangle((WIDTH/11) * 2, (HEIGHT/16) * 12, (WIDTH/14) * 9, HEIGHT/10); 
Rectangle leftInr = new Rectangle((WIDTH/11) * 2, HEIGHT/5, WIDTH/5, (HEIGHT/10) * 6); 
Rectangle rightInr = new Rectangle((WIDTH/12) * 6, (HEIGHT/20) * 7, WIDTH/2, (HEIGHT/10) * 3); 
//create finishLine 
Rectangle finishLine = new Rectangle(WIDTH/10, (HEIGHT/10) * 8, WIDTH/10, HEIGHT/70); 
//create checkpoint 
Rectangle checkPoint = new Rectangle((WIDTH/25) * 9, (HEIGHT/10) * 5, WIDTH/7, HEIGHT/70); 
//set Global Cars 
Rectangle carOne = new Rectangle(WIDTH/8, HEIGHT/2, WIDTH/30, WIDTH/30); 
Rectangle carTwo = new Rectangle(WIDTH/9, HEIGHT/2, WIDTH/30, WIDTH/30); 

public gameStart() { 
    super("Racing Game"); //set title 
    setSize(400, 400); //set the size 
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //make sure it closes when you click the exit button 
    setVisible(true); //make sure its visible 
    setResizable(false); 
    setLocationRelativeTo(null); //set location of JFrame to middle 
    /* 
    * Set the location 
    * First get the size of screen from Global variables 
    * Then use .setLocation(); with those variables 
    */ 

    //start double buffer 
    bufImg = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration().createCompatibleImage(WIDTH, HEIGHT); 

    //start cars up 
    moveMyCar moveCar = new moveMyCar(); 
    moveMyCar2 moveCar2 = new moveMyCar2(); 
    moveCar.start(); 
    moveCar2.start(); 
} 

@Override 
public void paint(Graphics g) { 
    Graphics2D gd = bufImg.createGraphics(); 
    try { 
     //setup double buffer in paint 
     gd.clearRect(0, 0, WIDTH, HEIGHT); 
     //draw finishline 
     gd.setColor(Color.RED); //set color 
     gd.fillRect(finishLine.x, finishLine.y, finishLine.width, finishLine.height); 
     //draw checkpoint 
     //gd.setColor(Color.CYAN); //set color 
     //gd.fillRect(checkPoint.x, checkPoint.y, checkPoint.width, checkPoint.height); 
     //draw track 
     //draw outside 
     gd.setColor(Color.LIGHT_GRAY); //set color 
     gd.fillRect(left.x, left.y, left.width, left.height); 
     gd.fillRect(right.x, right.y, right.width, right.height); 
     gd.fillRect(top.x, top.y, top.width, top.height); 
     gd.fillRect(bottom.x, bottom.y, bottom.width, bottom.height); 
     //draw inside 
     gd.fillRect(topInr.x, topInr.y, topInr.width, topInr.height); 
     gd.fillRect(bottomInr.x, bottomInr.y, bottomInr.width, bottomInr.height); 
     gd.fillRect(leftInr.x, leftInr.y, leftInr.width, leftInr.height); 
     gd.fillRect(rightInr.x, rightInr.y, rightInr.width, rightInr.height); 

     //draw car1 
     gd.setColor(Color.GREEN); // set color 
     //gd.fillRect(carOne.x, carOne.y, carOne.width, carOne.height); 
     gd.draw(carOne); 
     //draw car2 
     gd.setColor(Color.PINK); 
     //gd.fillRect(carTwo.x, carTwo.y, carTwo.width, carTwo.height); 
     gd.draw(carTwo); 
    } finally { 
     gd.dispose(); 
    } 

    g.drawImage(bufImg, 0, 0, this); 
} 

@Override 
public void update(Graphics g) { 
    paint(g); 
} 

private class moveMyCar extends Thread implements KeyListener { 
    @Override 
    public void run() { 
     addKeyListener(this); 
     while (true) { 
      try { 
       repaint(); 

       //check for collisions 
       if (carOne.intersects(left) || carOne.intersects(right) || carOne.intersects(top) || carOne.intersects(bottom) || carOne.intersects(topInr) || carOne.intersects(bottomInr) || carOne.intersects(leftInr) || carOne.intersects(rightInr)) { 
        if (cOspeed > 3.5) { 
         cOspeed = -5; 
        } 
        if (0 < cOspeed && cOspeed < 3.5) { 
         cOspeed = 1; 
        } 
       } 

       // check for laps 
       if (carOne.intersects(finishLine) && cODirection == UP && canLap == true) { 
        cOlaps++; 
        canLap = false; 
       } 
       if (carOne.intersects(checkPoint) && cODirection == DOWN) { 
        canLap = true; 
       } 

       // see if player won 
       if (cOlaps >= 3) { 
        winnerChosen = true; 
        JOptionPane.showMessageDialog(null, "Player 1 won the game!"); 
        break; 
       } 
       if (winnerChosen) { 
        break; 
       } 

       //increase speed 
       if (cOspeed <= 5) { 
        cOspeed += .2; 
       } 

       //change direction 
       if (cODirection == UP) { 
        carOne.y -= cOspeed; 
       } 
       if (cODirection == DOWN) { 
        carOne.y += cOspeed; 
       } 
       if (cODirection == LEFT) { 
        carOne.x -= cOspeed; 
       } 
       if (cODirection == RIGHT) { 
        carOne.x += cOspeed; 
       } 

       Thread.sleep(100); 

      } catch (Exception e) { 
       System.out.println("Error: " + e); 
       break; 
      } 
     } 
    } 

    public void keyPressed(KeyEvent event) { 
     if (event.getKeyChar() == ' ') { 
      if (cOspeed > -3) { 
       cOspeed -= 1; 
      } 
     } 
     System.out.println(event); 
    } 

    public void keyReleased(KeyEvent event) { 
    } 

    public void keyTyped(KeyEvent event) { 
     if (event.getKeyChar() == 'a') { 
      cODirection = LEFT; 
     } 
     if (event.getKeyChar() == 's') { 
      cODirection = DOWN; 
     } 
     if (event.getKeyChar() == 'd') { 
      cODirection = RIGHT; 
     } 
     if (event.getKeyChar() == 'w') { 
      cODirection = UP; 
     } 
    } 
} 

private class moveMyCar2 extends Thread implements KeyListener { 

    @Override 
    public void run() { 
     addKeyListener(this); 
     while (true) { 
      try { 
       repaint(); 

       //check for collisions 
       if (carTwo.intersects(left) || carTwo.intersects(right) || carTwo.intersects(top) || carTwo.intersects(bottom) || carTwo.intersects(topInr) || carTwo.intersects(bottomInr) || carTwo.intersects(leftInr) || carTwo.intersects(rightInr)) { 
        if (cTspeed > 3.5) { 
         cTspeed = -5; 
        } 
        if (0 < cTspeed && cTspeed < 3.5) { 
         cTspeed = 1; 
        } 
       } 

       // check for laps 
       if (carTwo.intersects(finishLine) && cTDirection == UP && canLapT == true) { 
        cTlaps++; 
        canLapT = false; 
       } 
       if (carTwo.intersects(checkPoint) && cTDirection == DOWN) { 
        canLapT = true; 
       } 

       // see if player won 
       if (cTlaps >= 3) { 
        winnerChosen = true; 
        JOptionPane.showMessageDialog(null, "Player 2 won the game!"); 
        break; 
       } 
       if (winnerChosen) { 
        break; 
       } 

       //increase speed 
       if (cTspeed <= 5) { 
        cTspeed += .2; 
       } 

       //change direction 
       if (cTDirection == UP) { 
        carTwo.y -= cTspeed; 
       } 
       if (cTDirection == DOWN) { 
        carTwo.y += cTspeed; 
       } 
       if (cTDirection == LEFT) { 
        carTwo.x -= cTspeed; 
       } 
       if (cTDirection == RIGHT) { 
        carTwo.x += cTspeed; 
       } 

       Thread.sleep(100); 

      } catch (Exception e) { 
       System.out.println("Error: " + e); 
       break; 
      } 
     } 
    } 

    public void keyPressed(KeyEvent event) { 
     if (event.getKeyChar() == 'm') { 
      if (cTspeed > -3) { 
       cTspeed -= 1; 
      } 
     } 
    } 

    public void keyReleased(KeyEvent event) { 
     System.out.println(event.getKeyCode()); 
    } 

    public void keyTyped(KeyEvent event) { 

     if (event.getKeyCode() == event.VK_LEFT) { 
      cTDirection = LEFT; 
     } 
     if (event.getKeyCode() == event.VK_DOWN) { 
      cTDirection = DOWN; 
     } 
     if (event.getKeyCode() == event.VK_RIGHT) { 
      cTDirection = RIGHT; 
     } 
     if (event.getKeyCode() == event.VK_UP) { 
      cTDirection = UP; 
     } 
     } 
    } 
} 

Voici mon code. Je me demandais deux choses. Tout d'abord, je reçois une erreur sur la ligne 80. Ligne 80 :

Graphics2D gd = bufImg.createGraphics(); 

Quoi qu'il en soit, il est une exception dans le thread « AWT-EventQueue-0 » java.lang.NullPointerException et je me demandais si je suppose que pour obtenir cette. Cela n'arrive pas à chaque fois, mais parfois. Si non, alors comment pourrais-je y remédier?

J'ai également utilisé les touches event.VK_ pour les touches fléchées Haut, Bas, Gauche et Droite et cela ne fonctionne pas. Il dit "accéder au champ statique". Que devrais-je faire à ce sujet?

Merci!

Answer 1

Je ferais ma peinture de fond dans un BufferedImage puis dessinerais le BufferedImage dans le paintComponent d'un JPanel. Vous pouvez en apprendre davantage sur la façon de faire quelque chose comme ça ici: painting in Swing

Par exemple, en utilisant votre code déjà créé:

import java.awt.*; 
import java.awt.image.BufferedImage; 
import javax.swing.*; 

public class GameStartJPanel extends JPanel { 
    private final static int WIDTH = 400, HEIGHT = 400; 

    private final static Rectangle left = new Rectangle(0, 0, WIDTH/10, HEIGHT); 
    private final static Rectangle right = new Rectangle((WIDTH/10) * 9, 0, WIDTH/5, HEIGHT); 
    private final static Rectangle top = new Rectangle(0, 0, WIDTH, HEIGHT/8); 
    private final static Rectangle bottom = new Rectangle(0, (HEIGHT/15) * 14, WIDTH, HEIGHT/9); 

    private final static Rectangle topInr = new Rectangle((WIDTH/11) * 2, (HEIGHT/16) * 3, (WIDTH/14) * 9, 
       HEIGHT/10); 
    private final static Rectangle bottomInr = new Rectangle((WIDTH/11) * 2, (HEIGHT/16) * 12, (WIDTH/14) * 9, 
       HEIGHT/10); 
    private final static Rectangle leftInr = new Rectangle((WIDTH/11) * 2, HEIGHT/5, WIDTH/5, (HEIGHT/10) * 6); 
    private final static Rectangle rightInr = new Rectangle((WIDTH/12) * 6, (HEIGHT/20) * 7, WIDTH/2, 
       (HEIGHT/10) * 3); 
    private final static Rectangle finishLine = new Rectangle(WIDTH/10, (HEIGHT/10) * 8, WIDTH/10, HEIGHT/70); 

    private final static Rectangle checkPoint = new Rectangle((WIDTH/25) * 9, (HEIGHT/10) * 5, WIDTH/7, HEIGHT/70); 

    private final static Rectangle carOne = new Rectangle(WIDTH/8, HEIGHT/2, WIDTH/30, WIDTH/30); 
    private final static Rectangle carTwo = new Rectangle(WIDTH/9, HEIGHT/2, WIDTH/30, WIDTH/30); 

    private BufferedImage backgroundImage; 

    public GameStartJPanel() { 
     backgroundImage = createBackgroundImage(); 
     setPreferredSize(new Dimension(WIDTH, HEIGHT)); 
    } 

    private BufferedImage createBackgroundImage() { 
     BufferedImage bckgdImage = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); 
     Graphics2D gd = bckgdImage.createGraphics(); 
     try { 

      gd.clearRect(0, 0, WIDTH, HEIGHT); 

      gd.setColor(Color.RED); 
      gd.fillRect(finishLine.x, finishLine.y, finishLine.width, finishLine.height); 

      gd.setColor(Color.LIGHT_GRAY); 
      gd.fillRect(left.x, left.y, left.width, left.height); 
      gd.fillRect(right.x, right.y, right.width, right.height); 
      gd.fillRect(top.x, top.y, top.width, top.height); 
      gd.fillRect(bottom.x, bottom.y, bottom.width, bottom.height); 

      gd.fillRect(topInr.x, topInr.y, topInr.width, topInr.height); 
      gd.fillRect(bottomInr.x, bottomInr.y, bottomInr.width, bottomInr.height); 
      gd.fillRect(leftInr.x, leftInr.y, leftInr.width, leftInr.height); 
      gd.fillRect(rightInr.x, rightInr.y, rightInr.width, rightInr.height); 

      // do this in the paintComponent method 
      // gd.setColor(Color.GREEN); 
      // gd.draw(carOne); 
      // gd.setColor(Color.PINK); 
      // gd.draw(carTwo); 
     } finally { 
      gd.dispose(); 
     } 

     return bckgdImage; 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     if (backgroundImage != null) { 
      g.drawImage(backgroundImage, 0, 0, null); 
     } 

     Graphics2D g2 = (Graphics2D) g; 
     g.setColor(Color.GREEN); 
     g2.draw(carOne); 
     g.setColor(Color.PINK); 
     g2.draw(carTwo); 
    } 

    private static void createAndShowUI() { 
     JFrame frame = new JFrame("GameStartJPanel"); 
     frame.getContentPane().add(new GameStartJPanel()); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.pack(); 
     frame.setLocationRelativeTo(null); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
     java.awt.EventQueue.invokeLater(new Runnable() { 
      public void run() { 
       createAndShowUI(); 
      } 
     }); 
    } 
}