Problem with collision Box2D [closed]

Question

I have been stuck with collisions in Cocos2d-x and Box2D for the past few days.

I have a class object: Ball

enum{

kActionIdle,
kActionBigger,
kActionCollision
}
Ball
{
    //variable
      m_actionState = kActionState ;
      bool m_collision;

//method
     startContact()  
     {
        if(m_actionState == kActionState)// i think it can't check this condition althought its' true
        sprite->runAction(action);//this line run normally if add in other function
     }

}
class MyContactListener : public b2ContactListener

  {
    void BeginContact(b2Contact* contact) {

      //check if fixture A was a ball
      void* bodyUserData = contact->GetFixtureA()->GetBody()->GetUserData();
      if ( bodyUserData )
        static_cast<Ball*>( bodyUserData )->startContact();

      //check if fixture B was a ball
      bodyUserData = contact->GetFixtureB()->GetBody()->GetUserData();
      if ( bodyUserData )
        static_cast<Ball*>( bodyUserData )->startContact();

    }

In method tick() of Box2D :

void tick(cctime dt)
{
    for(std::vector <Ball*>::iterator i = m_listBall->begin(); i!=m_ListBall->end(); i++) //this for run normally 
   {
     (*i)->startContact(); //i add breakpoint in here, and call function startContact, but not run action:(,
   }
}