JBox2d - world.getBodyList() goes into an infinite loop

Question

I'm trying to make a class that would draw objects of my JBox2d's world onto a canvas.

On update I have a call to

render.draw(canvas,world);

which passes the world and the canvas to the drawing class, which will be supposed to cycle through the world's objects and draw them into a canvas.

public void draw(Canvas canvas, World world)
{

    canvas.drawColor(0xFF6699FF);

    for ( Body b = world.getBodyList(); b!=null; b.getNext() )
    {
        Log.e("xy", String.valueOf( b.getPosition().x )+" "+String.valueOf( b.getPosition().y )  );
    }

}

yet it seems to go into an infinite loop, back button doesn't work, then it says "not responding" and offers to forceclose.

Any ideas what's the right way to cycle through the bodies in this case?

Thanks!

Seems to be right! :) I took this code from C++ and somehow didn't notice this moment. :) Thanks again! — Roger Travis, May 09 '12 at 13:08
Alright well I added it as an answer if you want to accept it! — BeRecursive, May 09 '12 at 22:54

score 6 · Accepted Answer · answered May 09 '12 at 22:54

6

As mentioned in my comment - the loop should be as follows:

for ( Body b = world.getBodyList(); b!=null; b = b.getNext() )
{
    Log.e("xy", String.valueOf(b.getPosition().x)+ " " + String.valueOf(b.getPosition().y));
}

answered May 09 '12 at 22:54

BeRecursive

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Jan-Terje Sørensen · Answer 2 · 2013-05-07T10:26:36.307

This is one way to do it. You get access to your different shapes (polygon / circle) through the world body list:

public void draw(Canvas canvas){
    Body body = world.getBodyList();
    while(body != null){
        Fixture fixture = body.getFixtureList();
        while(fixture != null){
            ShapeType type = fixture.getType();
            if(type == ShapeType.POLYGON){
                PolygonShape shape = (PolygonShape)fixture.getShape();
                // draw shape
            }else if(type == ShapeType.CIRCLE){
                CircleShape shape = (CircleShape)fixture.getShape();
                // draw shape
            }
            fixture = fixture.getNext();
        }
        body = body.getNext();
    }       
}

JBox2d - world.getBodyList() goes into an infinite loop

2 Answers2