need to update variables, main thread or different thread?

Question

Sorry if the question sounds stupid, I haven't been programming for too long, so I have this kind o newbie questions...

I have a JFrame (JFrame form from netBeans) with some variables(arrayList, int...). After a process, this variables change. The process is an mySQL query through JCDB driver, some arrayList update with data, which I use to fill a Jtable... and so on...

At first (poor me) I made a SwingWorker. Through the SwingWorker constructor, I pass these variables (about 6 variables more or less), and use them to do the processing and fill the tables.

I thought I would be able to update the value of these variables in the overriden Done() method (poor me again), and not just the GUI components.

I learned many things with this failure: 1) even though I passed the variables through the constructor, that doesn't mean they get updated in the place they come from. 2) SwingWorker can only return 1 variable, and modify GUI components.

So, and this is my main point, how can I do what I was trying to do? I learned it can't be done with SwingWorker class but then, how can it be done?

I don't want to put the code in an mouse click event just like that, because it would block my EDT with no notification to the user about what's happening.

I though about doing something like this: place the code inside a mouse click event, and show a Dialog so the user knows that a process is taking place at the moment.

private void jButton_calcular_rutaMousePressed(java.awt.event.MouseEvent evt) {                                                   
        // BOTON CALCULAR RUTA

        int index = jL_empGeo.getSelectedIndex();

        JOptionPane optionPane = new JOptionPane("Descargando ruta, espere por favor.", JOptionPane.INFORMATION_MESSAGE, JOptionPane.DEFAULT_OPTION, null, new Object[]{}, null);
        JDialog dialog = new JDialog();
        dialog.setTitle("Descarga");
        dialog.setModalityType(Dialog.DEFAULT_MODALITY_TYPE);

        dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);

        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        dialog.setLocation(dim.width / 2 - dialog.getSize().width / 2, dim.height / 2 - dialog.getSize().height / 2);
        dialog.setContentPane(optionPane);

        dialog.pack();

        dialog.setLocationRelativeTo(this);

        dialog.setVisible(true);

        //
        // THE PROCESSING TAKES PLACE HERE
        //
        //
        // mySQL query
        //
        // update arrayLists and variables
        //
        // update GUI components
        //
        //

        dialog.setVisible(false);
    }

Would this make any sense? is there any way to do the processing in a different Thread and afterwards get the arrayLists and variables back into the main thread?

Thanks in advance for your help.

EDIT

SwingWorker class

package descargas;

import clases.Empleados;
import clases.InfoPuntoRuta;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
import java.awt.Dimension;
import java.awt.Image;
import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.ImageIcon;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.SwingWorker;
import javax.swing.table.DefaultTableModel;
import maps.java.Geocoding;
import maps.java.Route;
import maps.java.StaticMaps;

public class ActualizarRuta2 extends SwingWorker<Void, Void> {

    int index;
    ArrayList<Empleados> arrayEmpleados;
    ArrayList<InfoPuntoRuta> listaPuntosRuta;
    DefaultTableModel modeloTablaRutas;
    JDialog dialog;
    ArrayList<String> listaIntermedios;
    JLabel jLab_RutaMAP;
    ImageIcon icono;
    int origenInt;
    int destinoInt;
    int destinoMax;

    public ActualizarRuta2(int index, int origenInt, int destinoInt, int destinoMax, ArrayList<Empleados> arrayEmpleados, ArrayList<InfoPuntoRuta> listaPuntosRuta, DefaultTableModel modeloTablaRutas, JDialog dialog, JLabel jLab_RutaMAP) {
        this.index = index;
        this.arrayEmpleados = arrayEmpleados;
        this.listaPuntosRuta = listaPuntosRuta;
        this.modeloTablaRutas = modeloTablaRutas;
        this.dialog = dialog;
        this.jLab_RutaMAP = jLab_RutaMAP;
        this.origenInt = origenInt;
        this.destinoInt = destinoInt;
        this.destinoMax = destinoMax;
    }

    @Override
    protected Void doInBackground() throws Exception {

        listaIntermedios = new ArrayList<String>();

        // recogemos la fecha actual
        DateFormat formatoFecha = new SimpleDateFormat("yyyy-MM-dd");
        Calendar cal = Calendar.getInstance();
        String dateMIN = formatoFecha.format(cal.getTime()) + " 00:00:01";
        String dateMAX = formatoFecha.format(cal.getTime()) + " 23:59:59";

        // GENERAR MAPA DE LA RUTA DEL DIA
        Connection conexion;
        conexion = conexiondb.ConexionDB.getConnection();
        if (conexion != null) {
            try {
                Statement st;
                ResultSet rs;

                st = (Statement) conexion.createStatement();
                rs = st.executeQuery("SELECT * \n"
                        + "FROM position\n"
                        + "WHERE nombre =  '" + arrayEmpleados.get(index) + "'\n"
                        + "AND position_date BETWEEN '" + dateMIN + "' AND '" + dateMAX + "'\n"
                        + "ORDER BY position_date;");

                // vaciamos la lista
                //listaPuntosRuta.clear();
                //System.out.println(rs.);
                // rellenamos la lista
                rs.beforeFirst();

                while (rs.next()) {
                    InfoPuntoRuta punto = new InfoPuntoRuta(rs.getString("nombre"),
                            rs.getString("position_date"), rs.getDouble("latitud"),
                            rs.getDouble("longitud"));

                    Geocoding ObjGeocod = new Geocoding();
                    ArrayList<String> resultadoCI = ObjGeocod.getAddress(punto.getLatitud(), punto.getLongitud());
                    String direccion = resultadoCI.get(0);

                    punto.setDireccion(direccion);

                    listaIntermedios.add(direccion);
                    listaPuntosRuta.add(punto);
                }

                //
                // DESCARGAR MAPA RUTA
                //
                int posicionUltimo = (listaIntermedios.size()) - 1;
                String origen, destino;

                ArrayList<String> waypoints = new ArrayList<String>();
                if (listaIntermedios.size() < 10) {
                    origen = listaIntermedios.get(0);
                    destino = listaIntermedios.get(posicionUltimo);
                    for (int i = 1; i < posicionUltimo; i++) {
                        waypoints.add(listaIntermedios.get(i));
                    }
                } else {
                    origen = listaIntermedios.get(0);
                    destino = listaIntermedios.get(9);
                    for (int i = 1; i < 9; i++) {
                        waypoints.add(listaIntermedios.get(i));
                    }
                }

//                ArrayList<String> prueba = new ArrayList<String>();
//                prueba.add("coruña avenida finisterre 65");
//                prueba.add("coruña ronda de outeiro 125");
//                prueba.add("coruña avenida del ejercito 20");
                Route ObjRout = new Route();

                String[][] resultadoRuta = ObjRout.getRoute(origen, destino, waypoints, Boolean.TRUE, Route.mode.driving, Route.avoids.nothing);
                //String[][] resultadoRuta = ObjRout.getRoute("Madrid", "Barcelona", prueba, Boolean.TRUE, Route.mode.driving, Route.avoids.nothing);
//                String[][] resultadoRuta = ObjRout.getRoute("coruña virrey ossorio 25", "pla y cancela, 16, 15005 la coruña, españa", prueba, Boolean.TRUE, Route.mode.driving, Route.avoids.nothing);
                String polylinea = ObjRout.getGeneralPolyline();
                StaticMaps ObjStatMap = new StaticMaps();
                Image resultadoMapa = ObjStatMap.getStaticMapRoute(new Dimension(585, 405), 1, StaticMaps.Format.png, StaticMaps.Maptype.hybrid, polylinea);
                icono = new ImageIcon(resultadoMapa);

                // RELLENAR TABLA DETALLES DE LA RUTA
                modeloTablaRutas.setRowCount(0);

            } catch (SQLException | UnsupportedEncodingException | MalformedURLException ex) {
                Logger.getLogger(ActualizarRuta2.class.getName()).log(Level.SEVERE, null, ex);
            } finally {
                try {
                    conexion.close();
                } catch (SQLException ex) {
                    Logger.getLogger(ActualizarRuta2.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        }
        return null;
    }

    @Override
    protected void done() {

        dialog.dispose();

        // RELLENAR TABLA DETALLES DE LA RUTA
        for (InfoPuntoRuta p : listaPuntosRuta) {
            modeloTablaRutas.addRow(new Object[]{
                p.getNombre(), p.getFecha(), p.getDireccion()});
        }

        // ponemos la imagen de la ruta
        jLab_RutaMAP.setIcon(icono);

        //
        listaIntermedios.clear();

//        listaPuntosRuta.clear();
        origenInt = 0;
        destinoMax = listaPuntosRuta.size() - 1;
        if (destinoMax < 9) {
            destinoInt = destinoMax;
        } else {
            destinoInt = 9;
        }

    }

}

Mouse event where I call the SwingWorker

private void jButton_calcular_rutaMousePressed(java.awt.event.MouseEvent evt) {                                                   
        // BOTON CALCULAR RUTA

        int index = jL_empGeo.getSelectedIndex();

        JOptionPane optionPane = new JOptionPane("Descargando ruta, espere por favor.", JOptionPane.INFORMATION_MESSAGE, JOptionPane.DEFAULT_OPTION, null, new Object[]{}, null);
        JDialog dialog = new JDialog();
        dialog.setTitle("Descarga");
        dialog.setModalityType(Dialog.DEFAULT_MODALITY_TYPE);

        dialog.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);

        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        dialog.setLocation(dim.width / 2 - dialog.getSize().width / 2, dim.height / 2 - dialog.getSize().height / 2);
        dialog.setContentPane(optionPane);

        dialog.pack();

        dialog.setLocationRelativeTo(this);

        listaPuntosRuta.clear();
        modeloTablaRutas.setRowCount(0);
        ActualizarRuta2 task = new ActualizarRuta2(index, origenInt, destinoInt, destinoMax, arrayEmpleados, listaPuntosRuta, modeloTablaRutas, dialog, jLab_RutaMAP);
        task.execute();

        dialog.setVisible(true);

    }     

Answer 1

You need communication from your 'SwingWorker', back to the GUI. Java parameters are pass by value -- so therefore, you need some form of value holder.

Making a 'data bean' descending from Observable, is probably the simplest way.

public class QueryResults extends Observable {
    protected List<SomeItem> itemList;
    // getters and setters.
}

From your SwingWorker, you need to store the results & notify observers. Notification must be done on the event-dispatch thread, and javax.swing.SwingWorker provides built-in functionality to call SwingWorker.done() on the EDT.

I have used 'Void' types as a "result", since the data-holder already exists & we are just loading data into it. The UI should already be bound to (and observing) it. Something like this:

public class QueryWorker<Void,Void> extends SwingWorker {
    protected QueryResults holder;
    public QueryWorker (QueryResults holder) {
        this.holder = holder;  // keep the holder & put data into it.
    }

    @Override
    protected Void doInBackground() {
        // run the query..
    }
    @Override
    protected void done() {
        holder.notifyObservers();
    }
}

This is a simplified example. It omits the possibility, for example, of the UI wanting to read the result-hodler (for display refresh) in the middle of loading. Your alternative there is to keep the data bean separate from the observable reference to the bean.

Answer 2

is there any way to do the processing in a different Thread and afterwards get the arrayLists and variables back into the main thread?

Yes, there is. You can (and probably should) start a new thread after dialog.setVisible(true) using

new Thread() {
    @Override
    public void run() {
        getNewValues();
    }
}.start();

Once this job is done, from your "worker"-thread, you can invoke

EventQueue.invokeLater(new Runnable() {
    @Override
    public void run() {
        //overwrite existing variables, update GUI elements, trigger repaints, etc.
        dialog.setVisible(false);
    }
};

However, you should always try to separate your data from your view. That means: You probably should not invoke those actions from your worker thread, but implement the observer pattern to inform your GUI that the data has changed and to refresh itself.