Of course, silly me. My apologies.
I'm not sure if you are aware, but the runtime has evolved quite a bit since the stock version that came with cocos2d-x 3.0. For instance, IK support has been added since then. Additionally, the animation listener has been broken out into 4 listeners plus 4 track listeners (one for each type of event).
I tried to look at the runtime files in the v3.0 release and couldn't find why you would get those values sent to your animation listener. At first glance, at least, it looks like every time the animation listener is called with the ANIMATION_END event type, the event parameter is null and the loopCount is 0. event is only non-null, if type is ANIMATION_EVENT.
Is the spineboy.json you're using the one that ships with cocos2d-x, or with a more recent version of Spine? Or have you modified it? What I'm getting at here, is that you should double check that the animation has an Event timeline.
