title: Single Jump function
body: <p>I'm developing a game by andengine. I want my player can jump only one time. So I used contact listner.but it doesn't  always work.mostly works but not always. Check the codes and tell me the my error please.</p>
  
  <p>I have player object.and ten box2d static object.I didn't understand how can this contact listener detect collision between player and these box. Because I have other boxes too.for example: player, square and circle. why this contact listener detect between player and square? why not between circle and square?</p>
  
  <pre><code>    private ContactListener contactListener()
      {
          ContactListener contactListener = new ContactListener()
          {
              @Override
              public void beginContact(Contact contact)
              {
                  player.setJumping(false);
              }
  
              @Override
              public void endContact(Contact contact)
              {
                  player.setJumping(true);
  
              }   
           };
           return contactListener;
      }
  </code></pre>