add
Register an AvailabilityListener to be notified when music is determined to be available or not.
This listener will be automatically removed after first callback.
Note that the AvailabilityListener methods won't be called until the player has either successfully or unsuccessfully tried to contact Adaptr to get a list of streaming servers. Therefore, it is possible that offline music is available to clients before an AvailabilityListeners are called.
Parameters
event