title: How change body's friction when contact with ground has begun?
body: <p>I making platformer character controls, something like this -><a href="http://www.badlogicgames.com/wordpress/?p=2017" rel="nofollow">BOX2D platformer</a>
  I'm using ContactListener interface.
  My problem is(friction) with these lines from code in the link -> </p>
  
  <pre><code>if(!grounded) {
      playerPhysicsFixture.setFriction(0f);
      playerSensorFixture.setFriction(0f);            
  } else {
      if(!Gdx.input.isKeyPressed(Keys.A) &amp;&amp; !Gdx.input.isKeyPressed(Keys.D) &amp;&amp; stillTime &gt; 0.2) {
          playerPhysicsFixture.setFriction(100f);
          playerSensorFixture.setFriction(100f);
      }
      else {
          playerPhysicsFixture.setFriction(0.2f);
          playerSensorFixture.setFriction(0.2f);
      }
  }
  </code></pre>
  
  <p>I can't figure how to change friction when feet already in touch with ground. When I change the friction in onUpdate() method of my character, the friction of conact that already is started isn't changed. Can somebody help me with this issue?</p>