Changing Box2D Body from Kinematic to Dynamic after contact

Question

What is the correct way to change a Kinematic body into a dynamic body?

context - I have a dynamic body as a projectile which has to be fired at a kinematic body (it is kinematic because i am tweening it around the world in random movements). when the projectile makes contact with the kinematic body I would like it to become a dynamic body and be affected by gravity and I will apply a force to the contact point.

At the moment I am simply changing the type with in a menthod called by the contactListener

body.setType(BodyType.DynamicBody);

my biggest issue is that gravity is not acting on the body once it is changed to dynamic, so I'm pretty certain I'm going about this the wrong way.

Answer 1

Trying this myself this seems to be caused by the body still being in sleeping state after changing it to Dynamic. Bodies in sleeping state are not included in the physics calculation until they are awoken by colliding with another body. The solution to this is to manually awake the body:

bodyFound.setType(BodyType.DynamicBody);
bodyFound.setAwake(true); // awake the body to enable physics calculations

Answer 2

try it like this,

mPhysicsWorld.setContactListener(new ContactListener()
{
@Override
public void beginContact(Contact contact)
{
    final Body ballA = (Ball) pContact.getFixtureA().getBody();
    final Body ballB = (Ball) pContact.getFixtureB().getBody();

    Body bodyFound;//find body of interest from ballA.getUserData(); and ballB.getUserData();

    runOnUpdateThread(new Runnable()
    {
        @Override
        public void run()
        {
            //I hope you have used: "physicsWorld.registerPhysicsConnector(new PhysicsConnector(sprite,body,true,false));" while creating bodies
            bodyFound.setType(BodyType.DynamicBody);
            //now it will respond to gravity
        }
    }
}
};

if still it do not respond on gravity than update gravity on scene.onUpdate() method, physicsWorld.setGravity(Vector2 yourGravity);