private MenuItem logoutMI;

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    logoutMI = menu.add(0, 1, 0,"Logout").setIcon(R.drawable.ic_logout);
    logoutMI.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);
    logoutMI.setVisible(false);
    super.onCreateOptionsMenu(menu, inflater);
}

logoutMI.setVisible(true);

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    inflater.inflate(R.menu.menu, menu);
    logoutMI = menu.findItem(R.id.menu_item);
    super.onCreateOptionsMenu(menu, inflater);
}