How to check if two Box2d bodies collision / overlap at any moment?

Question

How can you check if 2 bodies(with 1 Fixture both) collide(overlaps)?

I know about the ContactListener that fires a method when they start colliding and when they stop. But is there a way to check it in any given moment? Like:

if(body1.overlaps(body2))...

Additional details, one of them is sensor. this is in libgdx.

Answer 1

You can apply setContactlistner to your world object like

world.setContactListener(new ContactListener() {

            @Override
        public void beginContact(Contact contact) {

         if(contact.getfixtureA.getBody().getUserData()=="body1"&&
               contact.getfixtureB.getBody().getUserData()=="body2")
            Colliding = true;
            System.out.println("Contact detected");
        }

        @Override
        public void endContact(Contact contact) {
            Colliding = false;
            System.out.println("Contact removed");
        }

        @Override
        public void postSolve(Contact arg0, ContactImpulse arg1) {
            // TODO Auto-generated method stub
        }

        @Override
        public void preSolve(Contact arg0, Manifold arg1) {
            // TODO Auto-generated method stub
        }
    });

The beginContact() method will always call whenever any body will overlap or touch another body.You can also get the information about the body by contact object like contact.getFixtureA().getBody().getUserData(); if you want to do something with them.And when they separate from each other EndContact() method will be called.

Hope This helps.

Answer 2

Just check if the contact you are looking for is in the contact list:

for (ContactEdge ce = body1.getContactList(); ce != null; ce = ce.next)
{
     if (ce.other == body2 && ce.contact.isTouching())
     {
         // Do what you want here

         break;
     }
}

Answer 3

You can create the variable collision: When equals 0, collision equals false; When equals 1, collision equals true;

So:

if(body1.overlaps(body2)==true)
{collision=1}
else
{collision=0}