draw a gameobject on playfield with OOP

[Ferdy Dunki Jacobs]

Hello all,

I'm new on this forum so i don't know if my post is at the right place...

I'm just practicing with OOP and inheritance for a game i want to make, i have a playfield with squares (gridlike playfield)
but... and here comes the question...
How can i draw an image on the playfield if i have a superclass called GameObject with 4 subclasses with their own image

my code for the playfield...
Class Game

package happergroep1;

import java.awt.*;

/**
 *
 * @author Patrick
 * @author Furby
 * @version 1.0
 */
public class Game extends javax.swing.JFrame {

    Playfield tekenPanel;

    /** Creates new form Game */
    public Game() {
        initComponents();                           //Vereist
        this.setLayout(new BorderLayout());
        tekenPanel = new Playfield(20, 20);
        this.add(tekenPanel, BorderLayout.CENTER);
        tekenPanel.setFocusable(true);
        tekenPanel.setRequestFocusEnabled(true);
        pack();                                     //Vereist

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

Class Playfield

    package happergroep1;

import java.awt.*;          //* pakt alles in java.awt

import javax.swing.*;       //* pakt alles in java.swing

/**
 *
 * @author Patrick
 * @author Furby
 * @version 1.0
 */
public class Playfield extends JPanel {

    Dimension d;        //d van Dimension
    public static final Dimension square = new Dimension(20, 20);

    Player player;

    public Playfield(int width, int height) {
        d = new Dimension(width, height);
        Color c = new Color(0, 255, 0);

        setLayout(null);
        setPreferredSize(new Dimension(d.width * square.width + 120, d.height * square.height));
        setBackground(c);
        setFocusable(true);

        //player = new Player("pacman.gif", this);
        //addKeyListener(player);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        
        for(int i =0; i < d.width; i++){
            for(int j =0; j < d.height; j++){
                g.drawRect(i * square.width, j * square.height, square.width, square.height);
            }
        }

//        happer.Draw(g);
    }

    @Override  //netbeans asked for this override
    public boolean imageUpdate(Image img, int flags, int x, int y, int w, int h)
        {
        super.imageUpdate(img, flags, x, y, w, h);
        repaint();
        return true;
    }

SuperClass GameObject

package happergroep1;

import java.awt.Image;

/**
 *
 * @author Furby
 */
public abstract class GameObject {

    Image plaatje;

    public enum gameObject {
        Happer, Player, Stone, Block
    }

    public GameObject()
    {
        //call all images here to draw it on the playfield
    }

SubClass Player

package happergroep1;

import java.awt.event.KeyListener;

/**
 *
 * @author Furby
 */
public class Player extends GameObject implements KeyListener {

    public Player() {
        //here i need an image
    }
}

SubClass Happer

package happergroep1;

import java.awt.Toolkit;


/**
 *
 * @author Furby
 */
public class Happer extends GameObject{
    
    public Happer() {
    //here needs to be an image   
    } 
}

SubClass Stone

package happergroep1;

/**
 *
 * @author Furby
 */
public class Stone extends GameObject {

    public Stone() {
    // here i want multiple images here at random positions
    }
}

SubClass Block

package happergroep1;

/**
 *
 * @author Furby
 */
public class Block extends GameObject {

    public Block() {
    //here i want multiple images here at random positions
    }
}

I tried everything i could think of to make an image pop up in my grid like playfield but nothing works
Please can someone help me with this?

If i'm not totally clear just ask me for more info that you need

[Stephan van Hulst]

Hi Ferdy. Welcome to CodeRanch!

First of all, when you post your classes, please post the class name/declaration as well. It's important to know what types they extend or implement.

You also speak of a class GameObject, and four subclasses. Please post them, because it's hard to tell what you want to achieve.

I also notice you make a call to super.paintComponent() twice, one should be sufficient. And you override imageUpdate(). Why?

[Ferdy Dunki Jacobs]

Sorry for the incomplete info, i edited my post and i hope that it is clear to you now,
and netbeans asked me for an override by imageUpdate(), i think because it is an superclass from netbeans that is hidden from our view.

[Stephan van Hulst]

Okay, you won't be able to do what you want from making objects being rendered from their constructor. Technically you can, but this would cause a huge amount of overhead (new objects would be created every time the playing field is redrawn).

You also don't need the subclasses. What you can do is have one final GameObject class that is responsible for drawing all the images. You map a type of object to an image, and each instance will keep track of their x-y position and draw their associated image at the correct location. Here is a skeleton:

final class Playfield extends JPanel implements Observer {

  private static final Map<Entity.Type, Image> IMAGES;

  static {
    // init IMAGES
  }

  private final Map<Entity, GameObject> gameObjects;
  private GameModel model;

  private final class GameObject {

    private final Entity entity;

    GameObject(Entity entity) {
      if (entity == null) {
        throw new NullPointerException();
      }

      this.entity = entity;
    }

    void render(Graphics g) {
      // draw the image associated with this object's entity
    }
  }

  Playfield() {
    gameObjects = new HashMap<Entity, GameObject>();
  }

  void setModel(GameModel model) {
    gameObjects.clear();
    this.model = model;
    
    if (model != null) {
      // initialize a game object for each entity in the model
      model.addObserver(this);
    }
  }

  public void update(Observable o, Object arg) {
    if (o != model) {
      return;
    }

    if (arg instanceof Entity) {
      Entity entity = (Entity) arg;
      GameObject object = gameObjects.get(entity);

      // the game changed something about entity, so update your game object (maybe by repainting it?)
    }

    else {
      repaint(); // repaint the whole field
    }
  }

  @Override
  protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    // draw playfield here

    Rectangle clip = g.getClipBounds();
    for (GameObject object: gameObjects.values()) {
      // if the object is part of the area you have to redraw, then call its render method
    }
  }
}

[Stephan van Hulst]

Note that the classes GameModel and Entity make up your game data. Entity is anything in your game, a happer, a block, a player, etc. Entity.Type is an enum that describes the type of the entity. GameModel is the model of your game. It keeps track of where all the entities are. It should extend Observable, so it can notify your JPanel of changes to the game.

[Ferdy Dunki Jacobs]

Thnx, i will look into it and try to fix it in the weekend

[Ferdy Dunki Jacobs]

thank you so much for all your help, it works now.
you are really a genius with java you can see this topic as solved

[Stephan van Hulst]

Glad it helped