Clean up registered listeners

[programmerr47]

Hi. Currently as I understand everything correctly we cleaning up views in onDestroyView method. Here was as I remember one of the latest discussion about this topic.

I agree with proposals, but could we enhance it a little bit? Currently we can hang listeners to views through bunch of annotations (for example @OnFocusChange). The question is: can we release those listeners (which we added by annotations) before cleaning up views?

[WonderCsabo]

We should definitely do this. However when we should cleanup in case of @EView(Group) and @EActivity. @dodgex wdyt?

[dodgex]

Sounds like a good idea. But it looks like it might become a bit complicated

from what i found from a short time of googling:

• some listeners (e.g.) focus can be removed by calling setOnFocusChangeListener with null
  -but others (e.g.) text change listener work on a add/remove mechanic so we have to store the handler here

[WonderCsabo]

We have to add a new method to ListenerHandler, generateRemoveListener() or sg like this, and implement it in each listener. And yeah, we have to store the listeners in a field. :(

It is a bigger task.