Thread: [Java AWT (No Swing)] - Problem with hiding user-drawn graphics

Hello everyone,

I'm creating a game called Mouse Trap and I'm having an issue with a graphic drawn using AWT. Basically, when the mouse collides with the cheese, I want the cheese to disappear, or call (cheese[i].hide()). However, the cheese does not appear. hide() works for all other objects that inherit from PFigure, but the cheese will not. It's created a major issue in my game, and basically the only task left to accomplish.

I believe my problem lies within Cheese.java, method draw(). For example, if I replace it with an example drawing, this problem goes away!:

   public void draw()
   {
      Graphics g = panel.getGraphics();
      g.setColor(Color.blue);
      g.drawOval(x + width / 4 , y + 1, width / 2, height / 2);
      g.setColor(Color.red);
      g.drawLine( x + width / 2, y + height / 2 + 1, x + width / 2, y + 3 * height / 4 );
      g.setColor(Color.green);
      g.drawLine( x + width / 4, y + 5 * height / 8 + 1, x + 3 * width / 4, y + 5 * height / 8 + 1);
      g.setColor(Color.blue);
      g.drawLine( x + width / 2, y + 3 * height / 4, x + width / 4, y + 7 * height / 8 );
      g.drawLine( x + width / 2, y + 3 * height / 4, x + 3 * width / 4, y + 7 * height / 8 );
   }

I am open to any questions to explain my problem further if needed. I have three classes below that most likely involve the problem, feel free to ask if you need the others.

PFigure.java (This class cannot be changed as a requirement to my project)

import java.awt.*;
 
public abstract class PFigure implements Comparable
{
   protected int x, y;           // Current position of the figure
   protected int width, height;  // Drawn (displayed) this size
   protected int priority;       // Can use to determine "winner"
   protected Panel panel;        // Panel the figure lives on
 
   public PFigure ( int startX, int startY, int _width, int _height, 
                    int pr, Panel p )
   {
       x = startX;
       y = startY;
       width = _width;
       height = _height;
       priority = pr;
       panel = p;
   }
 
   // Can use this in "battles", which figures is "greater"
   public int compareTo(Object o)
   {
      if( o instanceof PFigure )
         return priority - ((PFigure)o).priority;
      return Integer.MAX_VALUE;
   }
 
   // Has "this" figure collided with p?
   public boolean collidedWith ( PFigure p )
   {
      if (  p == null )
         return false;
 
      return ( x + width ) >= p.x && ( p.x + p.width ) >= x &&
             ( y + height ) >= p.y && ( p.y + p.height ) >= y;
   }
 
   // Can be used for moving by keyboard or mouse
   public void move ( int deltaX, int deltaY )
   {
      x = x + deltaX;
      y = y + deltaY;
   }
 
   public void hide()
   {
      Graphics g = panel.getGraphics();
      Color oldColor = g.getColor();
      g.setColor(panel.getBackground());
      g.fillRect(x, y, width, height);
      g.setColor(oldColor);
   }
 
   // Can be automatic move, for example, called based on timer
   public void move()
   {
   }
 
 
   // Draw the figure.
   // Each derived class will write their own drawing method.
   // The first line should be:
   //    Graphics g = panel.getGraphics();
   abstract public void draw();
 
 
}

Cheese.java

import java.awt.*;
 
public class Cheese extends PFigure
{
 
   public Cheese(int startX, int startY, Panel p)
   {
      super(startX, startY, 60, 50, 0, p);
   }
 
   @Override
   public void draw()
   {
      Polygon cheese = new Polygon(); //
      cheese.addPoint(x , y);
      cheese.addPoint(x + 60, y);
      cheese.addPoint(x + 20, y - 50);
 
      Graphics g = panel.getGraphics();
      g.setColor(Color.yellow);
      g.fillPolygon(cheese);
      g.setColor(Color.black);
      g.drawPolygon(cheese);
      g.drawOval(x + 17, y - 32, width / 4, height / 4);
      g.drawOval(x + 11, y - 15, width / 5, height / 5);
      g.drawOval(x + 30, y - 15, width / 5, height / 5);
   }
 
}

MouseTrapGame.java

import java.awt.*;
import java.awt.event.ActionEvent;
 
public class MouseTrapGame extends java.awt.Frame
                           implements java.awt.event.ActionListener {
 
   private PFigureList listOfFigures = new PFigureList();
   private Mouse mouse;
   private MouseTrap mouseTrap;
   private Broom broom;
   private Cheese[] cheeses = new Cheese[5];
 
   private Dialog winMsg = new Dialog(this);
   private Dialog loseMsg = new Dialog(this);
 
   private int cheeseLeft = 5;
 
   private javax.swing.Timer moveTimer = new javax.swing.Timer(200, this);
 
   /**
    * Creates new form MouseTrapGame
    */
   public MouseTrapGame()
   {     
      initComponents();
      setSize(1000, 800);
      setLocationRelativeTo(null);
      spawnCheese();
      spawnTraps();
      spawnBrooms();
      mouse = new Mouse(gamePanel);      
      gamePanel.requestFocus();
      moveTimer.start();
   }
 
   private void displayWin()
   {
      winMsg.add(new Label("Congratulations! You won!"));
      winMsg.setSize(200, 100);
      winMsg.setLocationRelativeTo(null);
      winMsg.setVisible(true);
   }
 
   private void displayLose()
   {
      loseMsg.add(new Label("You lose..."));
      loseMsg.setSize(150, 100);
      loseMsg.setLocationRelativeTo(null);
      loseMsg.setVisible(true);
   }
 
   @Override
   public void actionPerformed(ActionEvent ae)
   {
      if (listOfFigures.checkCollision(mouse))
      {
         moveTimer.stop();
         displayLose();
      }
      if (cheeseLeft == 0)
      {
         moveTimer.stop();
         displayWin();
      }
      mouse.draw();
      for (int i = 0; i < 5; i++)
         cheeses[i].draw();
      listOfFigures.hideAll();
      listOfFigures.moveAll();
      listOfFigures.drawAll();
      cheeseLeftField.setText(String.valueOf(cheeseLeft));      
   }
 
   private void spawnTraps()
   {
      int startX;
      int startY;
      for (int i = 0; i < 4; i++)
      {
         startX = 200 + (int) (Math.random() * 700);
         startY = 50 + (int) (Math.random() * 650);
         mouseTrap = new MouseTrap(startX, startY, gamePanel);
         listOfFigures.add(mouseTrap);
      }
   }
 
   private void spawnBrooms()
   {
      int startX;
      int startY;
      for (int i = 0; i < 4; i++)
      {
         startX = 200 + (int) (Math.random() * 700);
         startY = 50 + (int) (Math.random() * 650);
         broom = new Broom(startX, startY, gamePanel);
         listOfFigures.add(broom);
      }
   }
 
   private void spawnCheese()
   {
      int startX;
      int startY;
 
      for (int i = 0; i < 5; i++)
      {
         startX = 20 + (int) (Math.random() * 750);
         startY = 20 + (int) (Math.random() * 600);
         cheeses[i] = new Cheese(startX, startY, gamePanel);
         System.out.println(startX);
         System.out.println(startY);
      }
   }
 
   /**
    * This method is called from within the constructor to initialize the
    * form. WARNING: Do NOT modify this code. The content of this method is
    * always regenerated by the Form Editor.
    */
   // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
   private void initComponents() {
 
      gamePanel = new java.awt.Panel();
      cheeseLeftLabel = new java.awt.Label();
      cheeseLeftField = new java.awt.TextField();
 
      setMinimumSize(new java.awt.Dimension(1000, 800));
      setTitle("Mouse Trap Game 243");
      addWindowListener(new java.awt.event.WindowAdapter() {
         public void windowClosing(java.awt.event.WindowEvent evt) {
            exitForm(evt);
         }
      });
      setLayout(null);
 
      gamePanel.setBackground(new java.awt.Color(0, 153, 153));
      gamePanel.addKeyListener(new java.awt.event.KeyAdapter() {
         public void keyPressed(java.awt.event.KeyEvent evt) {
            mouseMover(evt);
         }
      });
      add(gamePanel);
      gamePanel.setBounds(0, 0, 1000, 750);
 
      cheeseLeftLabel.setFont(new java.awt.Font("Dialog", 0, 18)); // NOI18N
      cheeseLeftLabel.setText("Cheese Left:");
      add(cheeseLeftLabel);
      cheeseLeftLabel.setBounds(375, 750, 120, 30);
 
      cheeseLeftField.setName(""); // NOI18N
      add(cheeseLeftField);
      cheeseLeftField.setBounds(510, 760, 70, 20);
 
      pack();
   }// </editor-fold>//GEN-END:initComponents
 
   /**
    * Exit the Application
    */
    private void exitForm(java.awt.event.WindowEvent evt) {//GEN-FIRST:event_exitForm
       System.exit(0);
    }//GEN-LAST:event_exitForm
 
   private void mouseMover(java.awt.event.KeyEvent evt) {//GEN-FIRST:event_mouseMover
      mouse.hide();
      if (evt.getKeyCode() == java.awt.event.KeyEvent.VK_DOWN)
         mouse.move(0, 10);
      else if ( evt.getKeyCode() == java.awt.event.KeyEvent.VK_UP )
         mouse.move(0, -10);
      else if ( evt.getKeyCode() == java.awt.event.KeyEvent.VK_LEFT )
         mouse.move(-10, 0);
      else if ( evt.getKeyCode() == java.awt.event.KeyEvent.VK_RIGHT )
         mouse.move(10, 0);
      mouse.draw();
 
      for (int i = 0; i < cheeseLeft; i++)
         if (mouse.collidedWith(cheeses[i]))
         {
            cheeses[i].hide();
            cheeseLeft--;
         }
 
   }//GEN-LAST:event_mouseMover
 
   /**
    * @param args the command line arguments
    */
   public static void main(String args[]) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            new MouseTrapGame().setVisible(true);
         }
      });
   }
   // Variables declaration - do not modify//GEN-BEGIN:variables
   private java.awt.TextField cheeseLeftField;
   private java.awt.Label cheeseLeftLabel;
   private java.awt.Panel gamePanel;
   // End of variables declaration//GEN-END:variables
}

I'm not sure on how I could slim down my program to just show the problem.

Here is a link to download the program folder (this way the images used in the game are also included) if that helps...

Download Prog5.zip @ UppIT

If you can get this to run, the problem is when the mouse touches the cheese. Even though my key event tells the cheese to hide(), the cheese is not erased and drawn at another location. This only happens with user graphically-drawn images. The images that are loaded from file all work fine.