Collision dectection

[jazzermonty]

Hi folks

Back again. Trying to register two moving objects intersecting on the frame. Code as follows:

 public Rectangle drawBat()
    {
        x = new Rectangle(batX, batY, breadth, length);
        return x;
        
    }
    public Rectangle drawBall()
    {
        o = new Rectangle(ballX, ballY, circumference, circumference);
        return o;
    }
    public void collision(Rectangle o, Rectangle x)
    {
        o = drawBall();
        x = drawBat();
        if(o.intersects(x));
        {
            System.out.println(x.x + "..." + x.y + "..." + o.x + ".." + o.y);
        }
    }

But no matter what, collision always prints the line. I've even tried if(!o.intersects(x)); to see what happened and I still get the output. Any hints?

Thanks

[KevinWorkman]

If you want help, you have to provide an SSCCE. You're using a few variables there whose values are completely unknown to us, which makes it impossible to help you.

Have you tried drawing the objects on the screen? Do they indeed intersect?

[jazzermonty]

If you want help, you have to provide an SSCCE. You're using a few variables there whose values are completely unknown to us, which makes it impossible to help you.

Have you tried drawing the objects on the screen? Do they indeed intersect?

Hi Kevin

Appologies. Variables declaration as follows:

this.breadth = 10;
        this.circumference= 60;
        this.batLength = 125;
        this.batY = 160;
        this.batX = 460;
        this.ballX = 200;
        this.ballY = 250;

The bat and ball move about the screen using an external container within another class, and yes, the do intersect (or not, depending on the position of the bat or ball.

But the method above 'collision' always prints the line, wither it's true or false.

Thanks

[jazzermonty]

Ok, I realise I'm not being very clear here. Let me put this in context. I have a JPanel that draws the bat and ball on screen. The bat moves depending on the arrow keys (this works) and the ballbounces about on screen( this works) if it hits the edge of the screen. I now want to detect the collision point of the bat and ball. batY changes depending on the arrow up or arrow down. The ball moves about using an offset.

Is this enough?

[Norm]

want to detect the collision point of the bat and ball.

Draw a picture of the ball and bat when they are colliding.
Write on the drawing their x,y location. Now do some arithmetic to compute the x,y using the size of each to determine when they are colliding.
Draw another picture where the ball and bat are not colliding and verify on it that your formulas for when they collide is correct when they are not colliding.

Look at the Polygon class. It has methods that can help.

[jazzermonty]

Draw a picture of the ball and bat when they are colliding.
Write on the drawing their x,y location. Now do some arithmetic to compute the x,y using the size of each to determine when they are colliding.
Draw another picture where the ball and bat are not colliding and verify on it that your formulas for when they collide is correct when they are not colliding.

Look at the Polygon class. It has methods that can help.

Sorry Norm, you lost me there. I thought the intersect() class would detect this for me, rather than(as I suspect your getting at) doing this longhand. Is this what you mean?

[Norm]

I made suggestions for two ways to do it. Your choice.

One could give you the x,y of where the collision occurred.
The other gives a true/false for if a collision occurred.

[Norm]

if(o.intersects(x));

[jazzermonty]

Sorry Norm, still not following.

I've been trying to implement this:

http://http://docs.oracle.com/javase...awt.Rectangle)

I've seen examples where this works, just not for me. And I'm doing what you say in your previous post (see line 5).

 public void collision(Rectangle o, Rectangle x)
    {
        o = drawBall();
        x = drawBat();
        if(!o.intersects(x));
        {
            System.out.println(x.x + "..." + x.y + "..." + o.x + ".." + o.y);
        }
    }

[Norm]

Look at post #8 and see what is colored RED

[jazzermonty]

Look at post #8 and see what is colored RED

Not seeing the RED (colour blindness sucks). Thanks for you patience.

[jazzermonty]

Ah, just got it. Thanks a lot Norm, really helpful.

You guys rock (bloomin syntax errors).

[Norm]

Bummer.
What is wrong with the compiler you are using. When I compile this statement I get a warning:

TestCode10.java:473: warning: [empty] empty statement after if
      if("x".equals("y"));
                         ^

[jazzermonty]

Bummer.
What is wrong with the compiler you are using. When I compile this statement I get a warning:

TestCode10.java:473: warning: [empty] empty statement after if
      if("x".equals("y"));


                         ^

Nothing, my java foo ain't soo good. I replied in post #12 where I realised what you were getting at. Cheers for your help once again.