public void showSortPopup(View v){

        PopupMenu sortMenu = new PopupMenu(this,v);
        listFragment = getFragmentManager().findFragmentById(R.id.mainActivityFrag);
        MenuInflater inflater = sortMenu.getMenuInflater();
        inflater.inflate(R.menu.sort_popup, sortMenu.getMenu());
        sortMenu.show();

        sortMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
            public boolean onMenuItemClick(MenuItem item) {
                int id = item.getItemId();
                switch (id) {
                    case R.id.action_sort_lastName:
                        MainActivityListFragment.lastName = true;
                        MainActivityListFragment.firstName = false;
                        break;
                    case R.id.action_sort_firstName:
                        MainActivityListFragment.lastName = false;
                        MainActivityListFragment.firstName = true;
                        break;
                    case R.id.action_sort_creationDate:
                        MainActivityListFragment.lastName = false;
                        MainActivityListFragment.firstName = false;
                        break;
                }
                listFragment.onActivityCreated(null);
                return true;

            }
        });

    }