Filter data in firebase and show in textview without button

I want to get details to autocomplete text view and when select that item then another text view show the sub category of that item without button click. as a example when the programme open load all category in autocomplete view i select biscuit then biscuit names load in next text(cream cracker,lomon puff) view or autocoplete view without press button.if i select book then load in next text view copybook.i can do this when button click event.but want do without using button.i wan to do text change event. don't know which event use in text view for that