code: public void playSequentially(Animator... items) {
          if (items != null) {
              mNeedsSort = true;
              if (items.length == 1) {
                  play(items[0]);
              } else {
                  for (int i = 0; i < items.length - 1; ++i) {
                      play(items[i]).before(items[i+1]);
                  }
              }
          }
      }
docs: Sets up this AnimatorSet to play each of the supplied animations when the
  previous animation ends.
  
  @param items The animations that will be started one after another.