1

Okay, so I am trying to create a simple game where you shoot a missile and if it hits a wall it has to bounce back expect for the bottom wall were it will inactivate the missile to allow me to shoot a new missile. 

import java.awt.*;

public class Project2{
  public static final int PANEL_WIDTH = 300;
  public static final int PANEL_HEIGHT = 300;
  public static final int SLEEP_TIME = 50;
  public static final Color SHOOTER_COLOR = Color.RED;
  public static final Color BACKGROUND_COLOR = Color.WHITE;
  public static final int SHOOTER_SIZE = 20; //diameter of the shooter
  public static final int GUN_SIZE = 10; //length og the gun
  public static final int SHOOTER_POSITION_Y = PANEL_HEIGHT - SHOOTER_SIZE;
  public static final int SHOOTER_INITIAL_POSITION_X = 150;
  public static int shooterPositionX;
  public static int gunPositionX;
  public static int gunPositionY;
  public static int targetPositionX;
  public static final Color TARGET_COLOR = Color.BLUE;
  public static final int TARGET_POSITION_Y = 50;
  public static final int TARGET_SIZE = 20;
  public static final int KEY_SPACE =32;
  public static final int KEY_PAGE_UP = 33;
  public static final int KEY_HOME = 36;
  public static final int KEY_LEFT_ARROW = 37;
  public static final int KEY_UP_ARROW = 38;
  public static final int KEY_RIGHT_ARROW = 39;
  public static final int KEY_DOWN_ARROW = 40;
  public static double missilePositionX;
  public static double missilePositionY;
  public static double missileDeltaX;
  public static double missileDeltaY;
  public static boolean missileActive;
  public static final Color MISSILE_COLOR = Color.BLACK;
  public static final int MISSILE_SIZE =2;
  public static final double MISSILE_SPEED =1.0;
  public static int hitCount;
  public static final int TARGET_DELTA_X= 1;
  public static int targetDeltaX;
//  public static final Random.nextDouble();
  public static void initialize(){
    shooterPositionX = SHOOTER_INITIAL_POSITION_X;
    gunPositionX = 0;
    gunPositionY = GUN_SIZE;
    targetPositionX = 150;
    missileActive = false;
    hitCount = 0;
    targetDeltaX = 0;
  }

  public static void main(String[] args) {
    DrawingPanel panel = new DrawingPanel(PANEL_WIDTH, PANEL_HEIGHT);
    Graphics g = panel.getGraphics( );
    initialize();
    startGame(panel, g);

  }

  public static void drawAll(Graphics g){
    g.setColor(Color.BLACK);
    g.drawString("Project 2 by JR", 10, 15); // fix ""
    g.drawString("Hits: " + hitCount, 10, 30);
//    for(int i=0, i<=hitCount; i++){
//     
//    }
    // Hits: followed by a number of stars corresponding to the hit count.
    //Do not do this by calling g.drawString in a loop. Instead, make a single string with a
    //for loop, appending the appropriate number of stars. Then call g.drawString once.
    drawShooter(g, SHOOTER_COLOR);
    drawTarget(g, TARGET_COLOR);

  }

  public static void startGame(DrawingPanel panel, Graphics g) {
    for (int i = 0; i <= 10000; i++) {
      panel.sleep(SLEEP_TIME);
      handleKeys(panel, g);
//      moveTarget(g);
      drawAll(g);
      moveMissile(g);

    }
  }

  public static void drawShooter(Graphics g, Color c){
    g.setColor(c);
    g.fillOval(shooterPositionX-SHOOTER_SIZE/2, SHOOTER_POSITION_Y-SHOOTER_SIZE, SHOOTER_SIZE, SHOOTER_SIZE);
    g.drawLine(shooterPositionX, SHOOTER_POSITION_Y-SHOOTER_SIZE, shooterPositionX+gunPositionX, SHOOTER_POSITION_Y-SHOOTER_SIZE - GUN_SIZE);
  }

  public static void drawTarget(Graphics g, Color c){
    g.setColor(c);
    g.fillOval(targetPositionX-TARGET_SIZE/2, TARGET_POSITION_Y-TARGET_SIZE, TARGET_SIZE, TARGET_SIZE);
    g.drawLine(targetPositionX-TARGET_SIZE, TARGET_POSITION_Y+TARGET_SIZE/2, targetPositionX+TARGET_SIZE, TARGET_POSITION_Y+TARGET_SIZE/2);
  }

  public static void moveShooter(Graphics g, int deltaX){
    drawShooter(g, BACKGROUND_COLOR);
    shooterPositionX += deltaX;
    drawShooter(g, SHOOTER_COLOR);
    //does not allow you to move any part of the shooter off the screen.
  }

  public static void handleKeys(DrawingPanel panel, Graphics g){
    int keyCode = panel.getKeyCode();
    if (keyCode == KEY_SPACE)
      reset(g);
    else if (keyCode == KEY_RIGHT_ARROW)
      moveShooter(g,1);
    else if (keyCode == KEY_LEFT_ARROW)
      moveShooter(g,-1);
    else if (keyCode == KEY_HOME)
      moveGun(g,1);
    else if (keyCode == KEY_PAGE_UP)
      moveGun(g,-1);
    else if(keyCode == KEY_UP_ARROW)
      shootMissile(g);
  }

  public static void reset(Graphics g){
    g.setColor(BACKGROUND_COLOR);
    g.fillRect(0,0, PANEL_WIDTH, PANEL_HEIGHT);
    initialize();
  }

  public static void moveGun(Graphics g, int deltaX){
    drawShooter(g, BACKGROUND_COLOR);
    gunPositionX += deltaX;
    drawShooter(g, SHOOTER_COLOR);
    //Do not let gunPositionX have an absolute value larger than SHOOTER_SIZE.
  }

  public static void shootMissile(Graphics g){
    if(missileActive == false){
      missileActive = true;
      missilePositionX = shooterPositionX;
      missilePositionY = SHOOTER_POSITION_Y-SHOOTER_SIZE;
      missileDeltaX = 0;
      missileDeltaY = 0;
      missilePositionX += missileDeltaX;
      missilePositionY += missileDeltaY;
    }
  }

  public static void moveMissile(Graphics g){
    if(missileActive){
      drawMissile(g, BACKGROUND_COLOR);
      missilePositionX += missileDeltaX;
      missilePositionY += missileDeltaY;
      drawMissile(g, MISSILE_COLOR); 
      if(missilePositionY <= 0){
        missileDeltaY = -Math.abs(missileDeltaY);
        missilePositionY += missileDeltaY;
      }
      else if(missilePositionX >= 300){
        missilePositionX += missileDeltaX;
      }
      else if(missilePositionX <=0){
        missileDeltaX = -Math.abs(missileDeltaX);
        missilePositionX += missileDeltaX;
      }
      else if(missilePositionY >= 300){
        drawMissile(g, BACKGROUND_COLOR);
        missileActive = false;
      }
      if( detectHitTarget((int)missilePositionX, (int)missilePositionY, (int)MISSILE_SIZE/2, targetPositionX, TARGET_POSITION_Y, TARGET_SIZE/2)){
        hitCount ++;
        drawMissile(g, BACKGROUND_COLOR);//erase the missile;
        missileActive = false;
      }
    }
  }
  public static void drawMissile(Graphics g, Color c){
    g.setColor(c);
    g.fillOval((int)missilePositionX, (int)missilePositionY, MISSILE_SIZE, MISSILE_SIZE);
    missileDeltaY = - gunPositionY * MISSILE_SPEED;
    missileDeltaX = gunPositionX * MISSILE_SPEED;  
  }
  public static boolean detectHitTarget(int x1, int y1, int r1, int x2, int y2, int r2){
     if(Math.sqrt(Math.pow((x1 - x2), 2) + Math.pow((y1 - y2), 2)) <= r1 + r2){
      return true;
    }else{
      return false;}
  }
  public static void moveTarget(Graphics g){
//    drawTarget(g, BACKGROUND_COLOR);
//    targetPositionX += targetDeltaX;
//    if(targetPositionX >= 0){
//      targetPositionX = +Math.abs(targetDelta);
//    }
//    else if(targetPositionX <=300){
//      targetPositionX = -Math.abs(targetDelta);
//    }
//    if(Random >= .98){
//      targetDeltaX = 0;
//    }
//    else if(Random >= .96){
//      targetDeltaX =1;
//    }
//    else if(Random >= .94){
//      targetDleta = -1;
//    }
  }
}

so far the ball is just getting 'stuck' to the top wall or not even getting 'stuck' in the case of the side walls just going off the panel, instead of bouncing off and I can't seem to figure it out.

Drawing Panel

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.ArrayList;

public class DrawingPanel implements ActionListener {
 private static final String versionMessage = 
    "Drawing Panel version 1.1, January 25, 2015";
 private static final int DELAY = 100;  // delay between repaints in millis
 private static final boolean PRETTY = false;  // true to anti-alias
 private static boolean showStatus = false;
 private static final int MAX_KEY_BUF_SIZE = 10;

 private int width, height;    // dimensions of window frame
 private JFrame frame;         // overall window frame
 private JPanel panel;         // overall drawing surface
 private BufferedImage image;  // remembers drawing commands
 private Graphics2D g2;        // graphics context for painting
 private JLabel statusBar;     // status bar showing mouse position
 private volatile MouseEvent click;     // stores the last mouse click
 private volatile boolean pressed;      // true if the mouse is pressed
 private volatile MouseEvent move;      // stores the position of the mouse
 private ArrayList<KeyInfo> keys;

 // construct a drawing panel of given width and height enclosed in a window
 public DrawingPanel(int width, int height) {
   this.width = width;
   this.height = height;
   keys = new ArrayList<KeyInfo>();
   image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);

   statusBar = new JLabel(" ");
   statusBar.setBorder(BorderFactory.createLineBorder(Color.BLACK));
   statusBar.setText(versionMessage);

   panel = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
   panel.setBackground(Color.WHITE);
   panel.setPreferredSize(new Dimension(width, height));
   panel.add(new JLabel(new ImageIcon(image)));

   click = null;
   move = null;
   pressed = false;

   // listen to mouse movement
   MouseInputAdapter listener = new MouseInputAdapter() {
     public void mouseMoved(MouseEvent e) {
       pressed = false;
       move = e;
       if (showStatus)
          statusBar.setText("moved (" + e.getX() + ", " + e.getY() + ")");
     }

     public void mousePressed(MouseEvent e) {
       pressed = true;
       move = e;
       if (showStatus)
          statusBar.setText("pressed (" + e.getX() + ", " + e.getY() + ")");
     }

     public void mouseDragged(MouseEvent e) {
       pressed = true;
       move = e;
       if (showStatus)
          statusBar.setText("dragged (" + e.getX() + ", " + e.getY() + ")");
     }

     public void mouseReleased(MouseEvent e) {
       click = e;
       pressed = false;
       if (showStatus)
          statusBar.setText("released (" + e.getX() + ", " + e.getY() + ")");
     }

     public void mouseEntered(MouseEvent e) {
//       System.out.println("mouse entered");
       panel.requestFocus();
     }

   };
   panel.addMouseListener(listener);
   panel.addMouseMotionListener(listener);
   new DrawingPanelKeyListener();

   g2 = (Graphics2D)image.getGraphics();
   g2.setColor(Color.BLACK);
   if (PRETTY) {
     g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
     g2.setStroke(new BasicStroke(1.1f));
   }

   frame = new JFrame("Drawing Panel");
   frame.setResizable(false);
   try {
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // so that this works in an applet
   } catch (Exception e) {}
   frame.getContentPane().add(panel);
   frame.getContentPane().add(statusBar, "South");
   frame.pack();
   frame.setVisible(true);
   toFront();
   frame.requestFocus();

   // repaint timer so that the screen will update
   new Timer(DELAY, this).start();
 }

 public void showMouseStatus(boolean f) {
   showStatus = f;
 }

 public void addKeyListener(KeyListener listener) {
   panel.addKeyListener(listener);
   panel.requestFocus();
 }

 // used for an internal timer that keeps repainting
 public void actionPerformed(ActionEvent e) {
   panel.repaint();
 }

 // obtain the Graphics object to draw on the panel
 public Graphics2D getGraphics() {
   return g2;
 }

 // set the background color of the drawing panel
 public void setBackground(Color c) {
   panel.setBackground(c);
 }

 // show or hide the drawing panel on the screen
 public void setVisible(boolean visible) {
   frame.setVisible(visible);
 }

 // makes the program pause for the given amount of time,
 // allowing for animation
 public void sleep(int millis) {
   panel.repaint();
   try {
     Thread.sleep(millis);
   } catch (InterruptedException e) {}
 }

 // close the drawing panel
 public void close() {
   frame.dispose();
 }

 // makes drawing panel become the frontmost window on the screen
 public void toFront() {
   frame.toFront();
 }

 // return panel width
 public int getWidth() {
    return width;
 }

 // return panel height
 public int getHeight() {
    return height;
 }

 // return the X position of the mouse or -1
 public int getMouseX() {
   if (move == null) {
     return -1;
   } else {
     return move.getX();
   }
 }

 // return the Y position of the mouse or -1
 public int getMouseY() {
   if (move == null) {
     return -1;
   } else {
     return move.getY();
   }
 }

 // return the X position of the last click or -1
 public int getClickX() {
   if (click == null) {
     return -1;
   } else {
     return click.getX();
   }
 }

 // return the Y position of the last click or -1
 public int getClickY() {
   if (click == null) {
     return -1;
   } else {
     return click.getY();
   }
 }

 // return true if a mouse button is pressed
 public boolean mousePressed() {
   return pressed;
 }

 public synchronized int getKeyCode() {
   if (keys.size() == 0)
     return 0;
   return keys.remove(0).keyCode;
 }

  public synchronized char getKeyChar() {
   if (keys.size() == 0)
     return 0;
   return keys.remove(0).keyChar;
 }

  public synchronized int getKeysSize() {
    return keys.size();
  }

 private synchronized void insertKeyData(char c, int code) {
   keys.add(new KeyInfo(c,code));
   if (keys.size() > MAX_KEY_BUF_SIZE) {
     keys.remove(0);
//     System.out.println("Dropped key");
   }
 }

 private class KeyInfo {
   public int keyCode;
   public char keyChar;

   public KeyInfo(char keyChar, int keyCode) {
     this.keyCode = keyCode;
     this.keyChar = keyChar;
   }
 }

 private class DrawingPanelKeyListener implements KeyListener {

   int repeatCount = 0;

   public DrawingPanelKeyListener() {
     panel.addKeyListener(this);
     panel.requestFocus();
   }

   public void keyPressed(KeyEvent event) {
//     System.out.println("key pressed");
     repeatCount++;
     if ((repeatCount == 1) || (getKeysSize() < 2))
        insertKeyData(event.getKeyChar(),event.getKeyCode());
   }

   public void keyTyped(KeyEvent event) {
   }

   public void keyReleased(KeyEvent event) {
     repeatCount = 0;
   }

 }

}
Moy_Desu
  • 19
  • 7
  • Can you post your `DrawingPanel` class too? – pleft Oct 31 '16 at 14:37
  • i implemented @elefasGR solution, I did include the `drawMissile()` within the `if`'s to erase the previous instance and re draw the new one. I also did add and subtract 1 from the `if`'s with a 0 to keep the missile within the panel width. – Moy_Desu Oct 31 '16 at 16:26

1 Answers1

0

Your drawMissile method which is called inside moveMissile method everytime it is called it is re-initializing the missileDeltaY and missileDeltaX variables.

missileDeltaY = - gunPositionY * MISSILE_SPEED;
missileDeltaX = gunPositionX * MISSILE_SPEED;

So no matter what calculations take place in the rest body of the moveMissile method, those variables will take their default values hence no change of the trajectory when hitting the boundaries.

I have made some changes in your methods to help you figure out the solution, it looks like it is working if you shoot the missile to hit the left boundary

shootMissile

public static void shootMissile(Graphics g){
    if(missileActive == false){
        missileActive = true;
        missilePositionX = shooterPositionX;
        missilePositionY = SHOOTER_POSITION_Y-SHOOTER_SIZE;
        missileDeltaX = 0;
        missileDeltaY = 0;
        missilePositionX += missileDeltaX;
        missilePositionY += missileDeltaY;
        missileDeltaY = - gunPositionY * MISSILE_SPEED;
        missileDeltaX = gunPositionX * MISSILE_SPEED;
    }
}

moveMissile

public static void moveMissile(Graphics g){
    if(missileActive){
        drawMissile(g, BACKGROUND_COLOR);
        missilePositionX += missileDeltaX;
        missilePositionY += missileDeltaY;
        drawMissile(g, MISSILE_COLOR);
        if(missilePositionY <= 0){
            missileDeltaY = Math.abs(missileDeltaY);
            missilePositionY += missileDeltaY;
        }
        if(missilePositionX >= 300){
            missilePositionX += -Math.abs(missileDeltaX);
        }
        if(missilePositionX <=0){
            missileDeltaX = Math.abs(missileDeltaX);
            missilePositionX += missileDeltaX;
        }
        if(missilePositionY >= 300){
            drawMissile(g, BACKGROUND_COLOR);
            missileActive = false;
        }
        if( detectHitTarget((int)missilePositionX, (int)missilePositionY, (int)MISSILE_SIZE/2, targetPositionX, TARGET_POSITION_Y, TARGET_SIZE/2)){
            hitCount ++;
            drawMissile(g, BACKGROUND_COLOR);//erase the missile;
            missileActive = false;
        }
    }
}

drawMissile

public static void drawMissile(Graphics g, Color c){
    g.setColor(c);
    g.fillOval((int)missilePositionX, (int)missilePositionY, MISSILE_SIZE, MISSILE_SIZE);
}
pleft
  • 7,567
  • 2
  • 21
  • 45