Ошибка NullPointerException при импорте изображений

Question

Я работаю над двумерной игрой, и всякий раз, когда я импортирую изображения классов противника, это дает мне следующую ошибку при запуске игры. Всякий раз, когда изображения удаляются из игровой папки, игра проходит отлично. Любая помощь будет оценена.

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
    at OurGame.Board.checkCollisions(Board.java:69) 
    at OurGame.Board.actionPerformed(Board.java:40) 
    at javax.swing.Timer.fireActionPerformed(Unknown Source) 
    at javax.swing.Timer$DoPostEvent.run(Unknown Source) 
    at java.awt.event.InvocationEvent.dispatch(Unknown Source) 
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
    at java.awt.EventQueue.access$200(Unknown Source) 
    at java.awt.EventQueue$3.run(Unknown Source) 
    at java.awt.EventQueue$3.run(Unknown Source) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
    at java.awt.EventQueue.dispatchEvent(Unknown Source) 
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
    at java.awt.EventDispatchThread.run(Unknown Source) 

Все игровые классы, которые я поставил вместе, чтобы они могли общаться друг с другом. Здесь ниже я вставить все мои игровые классы:

//Frame.java//

package OurGame; 
import javax.swing.*;//imports the graphics of the JFrame, always comes after the package or a error will be received 

public class Frame { 

    public static void main(String[] args) 
    { 

     JFrame frame = new JFrame("A Game Designed For Kejsi!"); 

     frame.add(new Board());//goes to the constructor of board 

     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//when the frame is closed, it just exits it 
     frame.setSize(1024,768);//sets the size with the dimensions of the background picture 
     frame.setVisible(true);//makes it visible 

    } 

} 

//Board.java//

package OurGame; 
import java.awt.*; 
import javax.swing.*; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.awt.event.KeyAdapter; 
import java.awt.event.KeyEvent; 
import java.util.ArrayList; 

public class Board extends JPanel implements ActionListener, Runnable{//you need to extend the panel, cause this class is a panel 

    Girl p;//creates a instance of the girl 
    Image img;//this image will contain the background image 
    Timer time;//this is used because the frame is going to be updated, because I will move the character 
    int v =300; 
    Thread animator; 
    Enemy en; 
    Enemy en2; 

    boolean lost = false;//determines wether or not the game is lost 

    static Font font = new Font("SanSerif", Font.BOLD,24);//creates a new font used for writing inside the graphics/paint method 
    public Board() 
    { 

     p = new Girl(); 
     addKeyListener(new AL());//listens all the time for any keys pressed or released 
     setFocusable(true);// it allows or not a component to receive focus from mouse or keyboard. 
     ImageIcon i = new ImageIcon("C:/Users/Marjo/Desktop/GameI/test.png"); 
     img = i.getImage();//img stores background image 
     time = new Timer(2, this);//updates the screen every 5 milliseconds 
     time.start();//this will run a method for the action perform therefore we need to implement ActionListener 
     en = new Enemy(p.x+1000,500, "C:/Users/Marjo/Desktop/GameI/enemy.png"); 
     en2 = new Enemy(p.x+1200,400,"C:/Users/Marjo/Desktop/GameI/fish.png"); 

    } 

    public void actionPerformed(ActionEvent e) 
    { 
     checkCollisions();//checks for collisions every 5 milliseconds 
     ArrayList bullets = Girl.getBullets();//adds any new bullets every 5 milliseconds 

     for(int w = 0; w< bullets.size();w++) 
     { 
      Bullet m = (Bullet) bullets.get(w); 
      if(m.getVisible()==true)//if the bullet is visible it will move it 
      { 
       m.moveRight(); 
      } 
      else 
       bullets.remove(w);//if the bullet is not visible it will remove it 
     } 

     p.move();//makes the character move every 5 millisecond 
     repaint();//repaints every 5 milliseconds 
     if(p.x>400)//shows where the enemy spawns 
     { 
      en.move(p.getDx()); 
     } 
     if(p.x>500) 
     { 
      en2.move(p.getDx()); 
     } 
    } 


    public void checkCollisions()//checks for collisions 
    { 
     Rectangle r1 = en.getBounds(); 
     Rectangle r2 = en2.getBounds(); 

      ArrayList bullets = Girl.getBullets();//goes through all the bullets and checks for collisions with the enemies 

      for(int w = 0; w< bullets.size();w++) 
      { 
       Bullet m = (Bullet) bullets.get(w); 
       Rectangle m1 = m.getBounds(); 
       if(r1.intersects(m1) && en.isAlive())//if the bullet touches the enemy 
       { 
        en.isAlive=false; 
        m.visible=false; 
       } 
       else 
        if(r2.intersects(m1)&& en2.isAlive()) 
        { 
         en2.isAlive=false; 
         m.visible=false; 
        } 

      } 

      Rectangle d = p.getBounds(); 

      if(d.intersects(r1)&&en.isAlive==true) 
      { 
      lost = true; 
      } 

      else 
       if(d.intersects(r2)&&en2.isAlive==true) 
      { 
       lost = true; 
      } 

      else 
       lost = false; 
    } 



    boolean k = false; 
    public void paint(Graphics g) 
    { 
     if(lost)//determines what to do when the game is lost 
      { 
       System.out.println("YOU LOST THE GAME. Marjo's minions defeated you!"); 
       System.exit(0); 
      } 


     if(p.dy==2 && k == false)//when jumping we want animation(thread to start) 
     { 
      k = true; 
      animator = new Thread(this); 
      animator.start(); 
     } 


     super.paint(g); 
     Graphics2D g2d = (Graphics2D) g; 

     if((p.getX()-170)%2040 == 0)//if it is at 166,1166,2166 etc. checks every 2000 pixels 
      p.nx = 0; 
     if((p.getX()-1186)%2040 == 0)//like above... 
      p.nx2 = 0; 

     g2d.drawImage(img, 1000-p.nx2, 0, null);//without this the game would be blank, draws the background 

     if(p.getX()>166)//starts a new background after the first one finishes 
     { 
      g2d.drawImage(img, 1000-p.nx, 0, null);//without this the game would be blank, draws the background 
     } 

     g2d.drawImage(p.getImage(), p.left, v, null);//draws character and keeps its position updated thanks to getImage(),getX() and getY() 

     ArrayList bullets = Girl.getBullets(); 

     for(int w = 0; w< bullets.size();w++) 
     { 
      Bullet m = (Bullet) bullets.get(w); 
      g2d.drawImage(m.getImage(), m.getX(), m.getY(), null); 
     } 


     g2d.setFont(font); 
     g2d.setColor(Color.BLUE); 
     g2d.drawString("Ammo left: "+ p.ammo,400,20);//draws the text ammo left at 500 right and 20 down pixels (position) 

     //prints the enemy only after a certain point in the game 
     if(p.x>400) 
     { 
      if(en.isAlive == true) 
      { 
       g2d.drawImage(en.getImage(),en.getX(),en.getY(),null); 
      } 
     } 

     if(p.x>500) 
     { 
      if(en2.isAlive == true) 
      { 
       g2d.drawImage(en2.getImage(),en2.getX(),en2.getY(),null); 
      } 
     } 


    } 


    private class AL extends KeyAdapter{//just determines which key was pressed 

     public void keyReleased(KeyEvent e)//tells us which key was released 
     { 
      p.keyReleased(e); 
     } 

     public void keyPressed(KeyEvent e)//which key was pressed 
     { 
      p.keyPressed(e); 
     } 

    } 


    //this is used for threads (jumping) and is a result of implementing runnable 
    public void run() { 

     long beforeTime,timeDiff,sleep; 
     //weird method to time jumping animation, always use this 
     beforeTime = System.currentTimeMillis(); 
     while(done == false)//this will keep looping as long as the jump is not done 
     { 
      cycle(); 
      timeDiff = System.currentTimeMillis() - beforeTime; 
      sleep = 10/*the speed of jumping, maybe not, for speed look below at the v++,v-- crap*/ - timeDiff; 
      if(sleep <= 0) 
       sleep = 2; 
      try{ 
       Thread.sleep(sleep); 
      } catch(Exception e) 
      {} 
      beforeTime = System.currentTimeMillis(); 
     } 
     k = false; 
     h = false; 
     done = false; 
    } 
    //changes the y value of the character 
    boolean h = false;//when at the peak of jump 
    boolean done = false;//when done jumping 
    public void cycle() 
    { 
     if(h == false)//it will continue jumping up as long as it is not at max height 
      { 
       v-=5; 
       p.bullh = v;//the bullh value makes sure that bullets that are shot get shot at the same height with the character 
       //which is v, therefore the variable bullh is the height of the shot bullets 
      } 
     if(v==100)//h becomes true once at max height 
      { 
       h = true; 
       p.bullh = v; 
      } 
     if(h == true && v<=460)//once at max height it will start descending making sure it doesn't go under the ground 
      { 
       v+=5; 
       p.bullh = v; 
      } 
     if(v == 300)//the jump is finished 
      { 
       done = true; 
       p.bullh = v; 
      } 
    } 

} 

//Girl.java//

package OurGame; 

import java.awt.Image; 
import java.awt.Rectangle; 
import java.awt.event.KeyEvent; 
import java.util.ArrayList; 

import javax.swing.ImageIcon; 

public class Girl { 

    int x,dx,y,nx2,nx,left,dy;//the x coordinate and the change in the x coordinate 
    Image still; 
    ImageIcon i = new ImageIcon("C:/Users/Marjo/Desktop/GameI/still.png"); 
    //creates the girl, but moving to the left 
    ImageIcon l = new ImageIcon("C:/Users/Marjo/Desktop/GameI/stillLeft.png"); 
    static ArrayList bullets;//stores the bullets 
    int ammo = 30; 
    int bullh = 450; //I created this variable to make sure bullets get shot at same height 

    public Girl() 
    { 


     still = i.getImage(); 
     left = 150; 
     x = 150; 
     y = 300; 
     nx2 = 1000; 
     nx = 0; 
     bullets = new ArrayList(); 


    } 

    public static ArrayList getBullets() 
    { 
     return bullets; 
    } 

    public void fire()//if more than 0 ammo creates a new bullet and adds it to an array list to be displayed on screen 
    { 
     if(ammo>0) 
     { 
      ammo--; 
      Bullet z = new Bullet((left + 100),bullh + 100); 
      bullets.add(z); 
     } 
    } 

    public void move() 
    { 
     if(dx!=-2)//makes it move only to the right, but is fixed below 
     { 
      if(left + dx<=350) 
       left = left + dx;//this moves the actual character to the right since left controls the characters physical position without moving 
      //screen 
      else 
      { 
       x = x + dx; 
       nx2 = nx2 + dx; 
       nx = nx + dx; 
      } 
     } 
     else 
     { 
      if(left+dx > 0)//will move left if not out of screen 
      { 
       left = left + dx; 
      } 
     } 
    } 

    public Rectangle getBounds()//assumes the girl is a rectangle and gets its bounds 
    { 
     return new Rectangle(left,y,75,240); 
    } 

    public int getX() 
    { 
     return x; 
    } 

    public int getY() 
    { 
     return y; 
    } 

    public int getDx() 
    { 
     return dx; 
    } 

    public Image getImage() 
    { 
     return still; 
    } 

    public void keyPressed(KeyEvent e)//will move the character if a key is pressed 
    { 
     int key = e.getKeyCode();//the integer code for an actual key in the keyboard 

     if(key == KeyEvent.VK_LEFT) 
     { 
      dx = -2; 
      still = l.getImage(); 
     } 


     if(key == KeyEvent.VK_RIGHT) 
     { 
      dx = 2; 
      still = i.getImage(); 
     } 

     if(key == KeyEvent.VK_UP) 
     { 
      dy = 2; 
     } 
    } 

    public void keyReleased(KeyEvent e) 
    { 
     int key = e.getKeyCode();//the integer code for an actual key in the keyboard 

     if(key == KeyEvent.VK_LEFT) 
     dx = 0;//the character will stop if the keys are released 

     if(key == KeyEvent.VK_RIGHT) 
     dx = 0; 

     if(key == KeyEvent.VK_UP) 
      dy = 0; 

     if(key == KeyEvent.VK_SPACE) 
      fire(); 

    } 


} 

//Bullet.java//

package OurGame; 
import java.awt.*; 

import javax.swing.ImageIcon; 


public class Bullet { 

    int x,y; 
    Image img; 
    boolean visible;//the bullet will be visible unless it hits something or goes out of the screen 

    public Bullet(int startX, int startY) 
    { 
     x = startX; 
     y = startY; 
     ImageIcon newBullet = new ImageIcon("C:/Users/Marjo/Desktop/GameI/bullet.png");//the bullet picture stored in the hard drive 
     img = newBullet.getImage(); 
     visible = true;//the bullet is initially visible 
    } 

    public void moveRight() 
    { 
     x = x + 6;//the bullet will move 6 pixels per millisecond 

     if(x>1024)//if the bullet is outside the board it is no longer visible 
     { 
      visible = false; 
     } 
    } 

    public Rectangle getBounds()//assumes the bullet is a rectangle and gets its bounds 
    { 
     return new Rectangle(x,y,54,16); 
    } 

    public int getX() 
    { 
     return x; 
    } 

    public int getY() 
    { 
     return y; 
    } 

    public boolean getVisible() 
    { 
     return visible; 
    } 

    public Image getImage() 
    { 
     return img; 
    } 


} 



//Enemy.java// 

package OurGame;

импорт java.awt.Image; import java.awt.Rectangle;

импорт javax.swing.ImageIcon;

класс Enemy общественного {

Image img; 
int x,y; 
boolean isAlive = true; 

public Enemy(int startX, int startY, String location) 
{ 
    x = startX; 
    y = startY; 
    ImageIcon l = new ImageIcon(location);//the reason why we are doing this is because we want to use more than one appearance of an enemy 
    img = l.getImage(); 
} 


public Rectangle getBounds()//assumes is a rectangle and gets its bounds 
{ 
    return new Rectangle(x,y,175,175); 
} 



public int getX() 
{ 
    return x; 
} 

public int getY() 
{ 
    return y; 
} 

public boolean isAlive() 
{ 
    return isAlive; 
} 

public Image getImage() 
{ 
    return img; 
} 


public void move(int dx) 
{ 
    if(dx!=-2)//makes sure the enemies don't go further away 
    x = x-dx;//when the player moves the enemy seems to be moving from right to left 
} 

}

Answer 1

Вы начинаете свой таймер, перед тем как инициализировать en и en2. Таймерные вызовы checkCollisions() и en и en2 еще не инициализированы. Вот почему вы получаете NPE.