I currently have a SearchView in the action bar of my app. When I click the search icon, the SearchView expands and the keyboard pops up as expecte         
        
No need to use onBackPressed() method for this!! 
I found the solution, do only as I mentioned below so that the SearchView itself handle the on back button press event.
Inside your onCreateOptionsMenu() method, 
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    MenuItem menuItem = menu.findItem(R.id.action_search);
    SearchView searchview = (SearchView) menuItem.getActionView();
    searchview.setIconifiedByDefault(true);
    searchview.setQueryHint("Enter your keyword");
    searchview.setOnQueryTextListener(this); 
    super.onCreateOptionsMenu(menu, inflater);
}
In your menu.xml add showAsAction attribute and set its values as "always|collapseActionView"
And you're ready to go ;)
P.S. - I was searching for a solution from a long time and now I found one, hope it helps you all.