Adding Process To Fragment

I have a search bar inside my 'main' layout, i call this layout by returning it with fragment acitivity after calling by my "MainActivity.java". My question is, how can i add function for the searchbar so i will be able to search from my database? i can only display the layout and i don't know where do i need to put my function for searching data from my database.here is my code from my 'main.java'

public class Main extends Fragment{
    public Main(){}

    @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container,
           Bundle savedInstanceState) {

       View rootView = inflater.inflate(R.layout.main, container, false);
       return rootView;
   }    
}

Thanks a lot!