Java - graphics paint

Question

I'm trying to develop a Java brick breaker (like DxBall) game and I want to make the Ball object with its own draw method.

What I'm trying to do:

public class Ball {
  private int x, y, diameter;
  public void  Ball(){
    x = 0;
    y = 0; 
    diameter = 20;
  }

  public void draw(Graphics g){
    g.setPaint(Color.red);
    g.fillOval(x, y, diameter, diameter);
  }
}

Therefore, my game engine extends JFrame and its paintComponent method will call game objects draw method. To sum, is it proper way to do object oriented game in Java? What should my Ball class extend?

I want to apply these objects in my GameEngine class which is a JFrame. GameEngine does some calculations and changes my objects(Ball or Paddle) x,y or speed values and then it will call all drawable objects paint methods. — user1832093, Nov 17 '12 at 16:18
No, you cannot call a paint method, call a draw method instead. — Roman C, Nov 17 '12 at 16:22
Ok, look at [this](http://stackoverflow.com/questions/13164162/canvas-object-not-displaying-but-location-is-updating-correctly-in-java-applet/13166879#13166879) example my be this help you but it needs to convert to the light objects. — Roman C, Nov 17 '12 at 16:33

Reimeus · Answer 1 · 2012-11-17T16:12:37.070

If you wish to make Ball a graphical component, you could extend JComponent:

public class Ball extends JComponent {
    private int x;
    private int y
    private int diameter;

    public Ball() {
        x = 0; 
        y = 0; 
        diameter=20;
    }

    @Override
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.setPaint(Color.red);
        g.fillOval(x, y, diameter, diameter);          
    }
}

and simply call repaint when you wish to paint the component instead of a custom draw method.

Note: There's no return type for constructors.

score 3 · Answer 2 · answered Nov 17 '12 at 16:06

3

Your Ball class seems to look ok. It doesn't need to extend anything. You will need to pass the Graphics object from the paintComponent of your game object to the Ball draw method.

answered Nov 17 '12 at 16:06

Dan D.

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I tried to pass Graphics object to my Ball class however it failed. – user1832093 Nov 17 '12 at 16:15
1

The paintComponent method in the game class should call the Ball.draw(g) method. How did it fail? – Dan D. Nov 17 '12 at 16:23

Sri Harsha Chilakapati · Answer 3 · 2012-11-18T01:43:16.743

1

Your class is fine but I recommend extending a class. This class usually called as Sprite or Action or GameObject contains the basic information like

image (or animation), position, collision rect and some basic functions like get and set it's position, speed and some collision detection functions if you wish.

Some resources.

Hope they help. And to draw the object, do

g.drawImage(ball.image, ball.x, ball.y, null);

edited Nov 18 '12 at 01:43

answered Nov 17 '12 at 17:07

Sri Harsha Chilakapati

11,744
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In many games, the objects would extend a class `Actor` or `Sprite` or else which would contain the basic nature of any element in the game like it's `position, image, collision rect` etc., – Sri Harsha Chilakapati Nov 18 '12 at 01:27
I recommend extending the class. Sorry for my english. – Sri Harsha Chilakapati Nov 18 '12 at 01:28
I think you should edit more of that excellent 1st comment into your answer. It makes it more clear. :) – Andrew Thompson Nov 18 '12 at 01:30

Java - graphics paint

3 Answers3