Getting previous selected position

Hi,

selecting a position was working ok, but when I was retreiving the position, it wasn't Overrided, and I don't know why it was returning -1 all the time. 

I added the method and initialized the position at -1. Why do I initialize? if I don't, it initializes to null, so to 0, and the 0 position is the first item of the array, then it could make confusion.

So briefly, if nothing is selected, it returns -1. This "-1" could be ok for checking if something was selected or for "diselecting".