Errors happen when using World.destroyBody( Body body )

Question

on Android application using libgdx, when I use World.destroyBody( Body body ) method, once in a while the application suddenly shuts down.

Is there some setting I need to do with body collision or Box2DDebugRenderer before I destroy bodies?

Below is the source I use for destroying bodies.

private void deleteUnusedObject( ) { for( Iterator<Body> iter = mWorld.getBodies() ; iter.hasNext() ; ){ Body body = iter.next( ) ; if( body.getUserData( ) != null ) { Box2DUserData data = (Box2DUserData) body.getUserData( ) ; if( ! data.getActFlag() ) { if( body != null ) { mWorld.destroyBody( body ) ; } } } } }

Thanks

Do you have any error messages? Why would you check if the body != null in the inner if statement when it is first used in your first if statement body.getUserData() != null. Second, what does mWorld.destroyBody( body ); do? Do you have any other threads running? — Luis Estrada
– Luis Estrada, Commented Mar 2, 2012 at 15:01
Do you do any contact filtering? When do you call deleteUnusedObjects? Are you sure youre not storing and using any references to destroyed bodies somewhere? — Majd
– Majd, Commented Mar 4, 2012 at 12:16
Possible duplicate of What is the proper way to remove a box2d body from the world in libgdx? — Anko
– Anko, Commented Nov 7, 2015 at 19:13

Vaughan Hilts · Accepted Answer · 2012-08-03 14:58:52Z

4

If you are trying to destroy the body in a CollisonEvent, this happens mid-step so you can't do that. Your best bet is to build a list of objects you would like to destroy and have them removed next frame.

answered Aug 3, 2012 at 14:58

Vaughan Hilts

5,4591 gold badge34 silver badges58 bronze badges

\$\begingroup\$ This is most likely the problem. @minami I did post a solution here that you would need to call outside the world.step() gamedev.stackexchange.com/questions/27113/… \$\endgroup\$

Chuck D
– Chuck D

2012-08-03 20:57:52 +00:00
Commented Aug 3, 2012 at 20:57

Add a comment |

Siddharth · Accepted Answer · 2012-06-04 12:57:44Z

I also face the same problem in libgdx. But I found an alternate solution about this is. The following is the way to work same as destroyBody

world.step(0,0,0); body.setActive(false);

this will made body inactive in the physics world and in the dispose method we destroy the body.

Amplify91 · Accepted Answer · 2012-07-04 13:56:57Z

Make sure you are not trying to destroy the body inside of world.step(). If you are destroying it from a ContactListener or something similar, you'll have to mark the body to be destroyed later and not during world.setp().

Rudy_TM · Accepted Answer · 2012-08-03 16:05:45Z

In your render method check if the world is locked, with world.islocked(), if it isn´t locked, and call immediatly the destroy body.

I suppose that you error is an assertion from Box2D

render(float arg0) { if(!world.isLocked()) { destroy your bodies here . . . } }

Tiarsoft · Accepted Answer · 2013-04-02 08:40:18Z

This is the best way to do it, i read it in the Box2D manual. You have to call this just after CURRENT_WORLD.step(..,...,...);

Iterator<Body> i = mWorld.getBodies(); Body node=i.next(); while (i.hasNext()) { Body oBj=node; node=i.next(); Box2DUserData data = (Box2DUserData ) oBj.getUserData(); if(data!=null && !data.getActFlag()){ mWorld.destroyBody(oBj); } }

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