Reset/reactivate collision

Hi,
Somebody knows how can reactivate/reset collision for rigidbody after it has been moved? here is my code:

[java]public void collision(PhysicsCollisionEvent event) {
if(event.getNodeA().getName().contains(“Ground1”)||event.getNodeB().getName().contains(“Ground1”)){
if(event.getNodeA().getName().contains(“PlayerNode”)||event.getNodeB().getName().contains(“PlayerNode”)){
ground2.getControl(RigidBodyControl.class).setPhysicsLocation(
new Vector3f(0,0, ground1.getLocalTranslation().z+120));
fpsText.setText(“Collision detected GROUND1”);
}}
if(event.getNodeA().getName().contains(“Ground2”)||event.getNodeB().getName().contains(“Ground2”)){
if(event.getNodeA().getName().contains(“PlayerNode”)||event.getNodeB().getName().contains(“PlayerNode”)){
ground1.getControl(RigidBodyControl.class).setPhysicsLocation(
new Vector3f(0,0, ground2.getLocalTranslation().z+120));
player.setWalkDirection(new Vector3f(0f,0f,-0.5f));
fpsText.setText(“Collision detected GROUND2”);
}}

}[/java]

In my case collision btwn PlayerNode (CharacterControl) and ground1,ground2 is done only once after that no longer active (PlayerNode fall down)

http://hub.jmonkeyengine.org/javadoc/com/jme3/bullet/objects/PhysicsRigidBody.html#activate()

Sorry, but if I add lines:
[java] ground1.getControl(RigidBodyControl.class).activate();
ground2.getControl(RigidBodyControl.class).activate();[/java]
nothing happens

Well you set the location directly there, you have to make sure the positions make sense. Maybe your object gets stuck?