title: Start an animation from a task running on a background thread
body: <p>In my <code>MainActivity</code> I have a <code>callback</code> whose runs asynchronously on a background thread. I would like to show an <code>Animation</code> (rotation) over an <code>Imageview</code>  while the <code>thread</code> is running , so my callback is:</p>
  
  <pre><code>        pull.addChangeListener(new Replication.ChangeListener() {
              @Override
              public void changed(Replication.ChangeEvent event) {
  
                 if (REPLICATION_ACTIVE)) {
                      runOnUiThread(new Runnable() {
                          @Override
                          public void run() {
                             startAnimation();//I call here to the animation                              
                  } else {
                      runOnUiThread(new Runnable() {
                          @Override
                          public void run() {
                           stopAnimation()
                          }
                      });
                  }
  </code></pre>
  
  <p>The startAnimation() method </p>
  
  <pre><code> private void startAnimation(){
                  isAnimationDone = true;
                  imgSincronizacion.setImageResource(R.mipmap.btn_sync_on);
                  Animation rotation= AnimationUtils.loadAnimation(getApplicationContext(), R.anim.rotation);
                  rotacion.setRepeatMode(Animation.ABSOLUTE);
                  rotacion.setRepeatCount(Animation.INFINITE);
                  imgSincronizacion.startAnimation(rotation);
          }
  </code></pre>
  
  <p>Im not facing errors but the animation does not not work. Any idea about how I can animate an <code>ImageView</code> from a background <code>Thread</code> ?</p>