ComboBox help

Hi all:

When selecting a row and press the Edit button , I need to see the default item in the table , but while loading it first appears white and then I can select the item pre loaded, appreciate your help.

The code is:

UsuarioDAO uDAO = new UsuarioDAO();
        List<Usuario> c = uDAO.buscarPorId(id);
        for (int i = 0; i < uDAO.buscarPorId(id).size(); i++) {
            System.out.println("" + i);
            System.out.println("NOMBRE" + c.get(i).getNombre());

            txtNombre.setValue(c.get(i).getNombre());
            txtApepat.setValue(c.get(i).getApepat());
            txtApemat.setValue(c.get(i).getApemat());
            txtFono.setValue(c.get(i).getFono());
            txtCelular.setValue(c.get(i).getCelular());
           
            comboCiudad.addItem(c.get(i).getCiudad().getNombre());
           
            txtEstado.setValue(c.get(i).getEstado());
             comboCiudad.setNewItemsAllowed(true);
            
            comboCiudad.setImmediate(true);
        }

I leave attached image of what I currently have .