Playing Audio with Fade In/Out effect

Previously I was using the Timer() thread to create a Volume Fade In and Fade Out effects while playing the audio and setting up the volume in it. After upgrading to the latest version of ExoPlayer now I am getting the following error message:

> java.lang.IllegalStateException: Player is accessed on the wrong thread.
> Current thread: 'Timer-0'
> Expected thread: 'main'

I understand that ExoPlayer needs to accessed via same thread, but is there a way to create the Volume Fade In/Fade Out effect?

Thanks