Generating random sprites

General Discussions
#1 
package minigames;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class fallingball extends JPanel {
	
	
	int x = 250;
	int y = 0;
	
	private void moveBall() {
		y = y + 1;
		
		
	}
	

	public void paint(Graphics g){
		super.paint(g);
		Graphics2D g2d = (Graphics2D) g;
		g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
		g2d.setColor(Color.black);
		g2d.fillOval(x, y, 30, 30);
	}
	
	public static void main(String[] args) throws InterruptedException{
		JFrame f = new JFrame("Falling Ball");
		fallingball game = new fallingball();
		f.add(game);
		f.setSize(500, 500);
		f.setResizable(false);
		f.setLocationRelativeTo(null);
		f.setVisible(true);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		while (true) {
			game.moveBall();
			game.repaint();
			Thread.sleep(10);
		}
	}

}

only 1 ball is generated and it gets fallen down. i wanted to generate balls falling randomly and from different x co-ordinate in the frame how can i do that

#2

  1. This is kind of the wrong forum to post this kind of question.

  2. You have to create a loop if you want more balls to fall down.

  3. You have to randomly set the x-coordinate using maybe the java.util.Random class.

And last but not least: You don’t begin a question with a bunch of code. Maybe next time start with a little introduction on what you try to accomplish…

#3

oh m sorry but can u tell me where can i get hep for those types of problems. and m sorry for unusual topic in the incorrect place.

#4

Google Java Random and click on the link for the java documents site. Read up on it. Then learn the basic structure of a for loop. This is simple stuff, why did you get into graphics before learning the basics of the language?

#5

Maybe someone of the dukes could move this post to the right forum? :slight_smile:

I allready answered your questions. But it seems you kinda lack some java basics. Maybe you should start with that before trying to write games.

Here is an example for creating a random amount of balls with random x-coordinates:


public class FallingBallTest {

      private int[] balls; // Array of x values for the various balls
      private int y;
      private int width;
      public boolean running = false;

      public FallingBallTest() {
            JFrame f = new JFrame("Falling Ball Test");
            f.add(this);
            f.setSize(500, 500);
            f.setResizable(false);
            f.setLocationRelativeTo(null);
            f.setVisible(true);
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            width = this.getWidth();
            Random rand = new Random();
            balls = new int[rand.nextInt(10)];
            for(int i = 0; i < xCoords.length; i++)
            balls[i] = rand.nextInt(width);
            this.startGame();
      }

      public void startGame() {
            running = true;
            while(running) {
                  this.update();
                  this.repaint();
            }
      }

      public void update() {
            y++
      }

      public void paintComponent(Graphics g) {
            super.paint(g);
            Graphics2D g2d = (Graphics2D) g;
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            g2d.setColor(Color.black);
            for(int x : balls) {
                  g2d.fillOval(x, y, 30, 30);
            }
      }

      public void main(String[] args) {
            new FallingBallTest();
      }
}

I give no guarantee that it actually works, was just scribbling it here before i have to go :).

#6

The only thing I want to point out in your code so that the OP understands is that

xCoords[]

is actually the array of balls. Sorry but it seemed like a very vague and not related name for an array of balls!

#7

Thanks for pointing that out, i changed it :).

#8

I’d say you’re missing a few layers of useful abstraction. In particular a separate ball object and a rough entity system which is just a fancy term of “a list of sprites” basically. Also you should separate some of your logic into their own functions, your game loop for instance.

public class fallingball extends JPanel {
   
   // Make a list of balls
   List<Ball> balls = new ArrayList<Ball>();

   // separate the coordinates and move() function into its own Ball class
   class Ball { 
      int x;
      int y;

      Ball(int x, int y) {
         this.x = x;
         this.y = y;
      }
   
      void move() {
         y = y + 1;
      }
   }

   public void paint(Graphics g){
      super.paint(g);
      Graphics2D g2d = (Graphics2D) g;
      g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      g2d.setColor(Color.black);

      // go through every Ball in the list of balls and paint each one.
      for (int i = 0; i < balls.size(); i++) {
         Ball b = balls.get(i);
         g2d.fillOval(b.x, b.y, 30, 30);
      }
   }

   public void doGameLoop() {
      // go through every Ball in the list of balls and update each one.
      for (int i = 0; i < balls.size(); i++) {
         Ball b = balls.get(i);
         b.move();
      }
      game.repaint();
   }
   
   public static void main(String[] args) throws InterruptedException{
      JFrame f = new JFrame("Falling Ball");
      fallingball game = new fallingball();
      f.add(game);
      f.setSize(500, 500);
      f.setResizable(false);
      f.setLocationRelativeTo(null);
      f.setVisible(true);
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      
      // Create a new random generator
      Random r = new Random();

      // create 10 balls at random places
      for (int i = 0; i < 10; i++) {
         int x = r.nextInt(100);
         int y = 0;

         // Create the ball
         Ball ball = new Ball(x,y);

         // add the newly created ball to the list of balls.
         balls.add(ball);
      }

      while (true) {
         doGameLoop();
         Thread.sleep(10);
      }
   }

}
#9

I’d say the OP would need some more basic java, because that is what you learn when learning the basics of the language…

#10

I agree. I almost would go as far to say that he doesn’t know what classes are. Besides, for such a small project that extra ball class really isn’t needed.

#11

Kon, First, lets make things easier.

Make a Ball Class.

The ball class must contain some things ;

int positionX,positionY;

and two methods at least

update()
render()

Then to make random Numbers , you can use Math.Random(…);

But since you probably isnt so familiar with java,
i recommend two channels :

and

Hope it helps :stuck_out_tongue:

#12

OP really isn’t advanced enough to probably understand what you’re talking about. Plus, if you would’ve read the other posts, this question has already been answered a few times.

#13

I was just trying to help in a simple"r" way.

Plus i put the video tutorials if you would’ve read my post fully. :stuck_out_tongue: