code: public void addChannel(String boneName, GVRAnimationChannel channel)
      {
          int boneId = mSkeleton.getBoneIndex(boneName);
          if (boneId >= 0)
          {
              mBoneChannels[boneId] = channel;
              mSkeleton.setBoneOptions(boneId, GVRSkeleton.BONE_ANIMATE);
              Log.d("BONE", "Adding animation channel %d %s ", boneId, boneName);
          }
      }
docs: Add a channel to the animation to animate the named bone.
  @param boneName  name of bone to animate.
  @param channel   The animation channel.