ciao ho un problema stranissimo, quando provo ad eseguire questa classe:

codice:
package a_ApplicationLayer;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JPanel;

import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.axis.ValueAxis;
import org.jfree.chart.plot.XYPlot;
import org.jfree.data.XYDataset;
import org.jfree.data.time.Millisecond;
import org.jfree.data.time.TimeSeries;
import org.jfree.data.time.TimeSeriesCollection;
import org.jfree.ui.ApplicationFrame;
import org.jfree.ui.RefineryUtilities;
import b_BusinessLayer.BusinessUser;

/**
 * A demonstration application showing a time series chart where you can dynamically add
 * (random) data by clicking on a button.
 *
 */
public class DynamicDataDemo extends ApplicationFrame implements ActionListener {

    /** The time series data. */
    public TimeSeries series;
    private BusinessUser dati;
    /** The most recent value added. */
    private double lastValue = 100.0;
    /**
     * Constructs a new demonstration application.
     *
     * @param title  the frame title.
     */
    public DynamicDataDemo(final String title,BusinessUser dati) {

        super(title);
        this.series = new TimeSeries("Random Data", Millisecond.class);
        this.dati=dati;
        final TimeSeriesCollection dataset = new TimeSeriesCollection(this.series);
        final JFreeChart chart = createChart(dataset);
        
        final ChartPanel chartPanel = new ChartPanel(chart);
        final JButton button = new JButton("Add New Data Item");
        button.setActionCommand("ADD_DATA");
        button.addActionListener(this);

        final JPanel content = new JPanel(new BorderLayout());
        content.add(chartPanel);
        content.add(button, BorderLayout.SOUTH);
        chartPanel.setPreferredSize(new java.awt.Dimension(500, 270));
        setContentPane(content);


    }

    /**
     * Creates a sample chart.
     *
     * @param dataset  the dataset.
     *
     * @return A sample chart.
     */
    private JFreeChart createChart(final XYDataset dataset) {
        final JFreeChart result = ChartFactory.createTimeSeriesChart(
            "Dynamic Data Demo",
            "Time",
            "Value",
            dataset,
            true,
            true,
            false
        );
        final XYPlot plot = result.getXYPlot();
        ValueAxis axis = plot.getDomainAxis();
        axis.setAutoRange(true);
        axis.setFixedAutoRange(20000.0);  // 60 seconds
        axis = plot.getRangeAxis();
        axis.setRange(-100.0, 0.0);
        return result;
    }
    
    public void add_valore(double val){
      this.series.add(new Millisecond(),val);
    }
    
    public void registra(){
      for(int i=0;i<20;i++)
      {
        this.series.add(new Millisecond(),this.dati.getSegnale());
        System.out.println("ciao");
      }

    }

    //  ****************************************
************************************
    // * JFREECHART DEVELOPER GUIDE                                               *
    // * The JFreeChart Developer Guide, written by David Gilbert, is available   *
    // * to purchase from Object Refinery Limited:                                *
    // *                                                                          *
    // * http://www.object-refinery.com/jfreechart/guide.html                     *
    // *                                                                          *
    // * Sales are used to provide funding for the JFreeChart project - please    *
    // * support us so that we can continue developing free software.             *
    //  ****************************************
************************************

    /**
     * Handles a click on the button by adding new (random) data.
     *
     * @param e  the action event.
     */
    public void actionPerformed(final ActionEvent e) {

   
   }

    /**
     * Starting point for the demonstration application.
     *
     * @param args  ignored.
     */
    public static void main(final String[] args) {

      BusinessUser d= new BusinessUser();
      final DynamicDataDemo demo = new DynamicDataDemo("Dynamic Data Demo",d);
      demo.pack();
      RefineryUtilities.centerFrameOnScreen(demo);
      demo.setVisible(true);
      demo.series.add(new Millisecond(),d.getSegnale());
      demo.series.add(new Millisecond(),d.getSegnale());
      demo.series.add(new Millisecond(),d.getSegnale());


    }
la cosa stranissima è che se prendo tutto il codice presente nel Main quindi questo

codice:
      BusinessUser d= new BusinessUser();
      final DynamicDataDemo demo = new DynamicDataDemo("Dynamic Data Demo",d);
      demo.pack();
      RefineryUtilities.centerFrameOnScreen(demo);
      demo.setVisible(true);
      demo.series.add(new Millisecond(),d.getSegnale());
      demo.series.add(new Millisecond(),d.getSegnale());
      demo.series.add(new Millisecond(),d.getSegnale());


e lo collego ad un'evento di un bottone di un'altra finestra

il grafico mi si apre correttamente ma aspetta di creare tutti e tre i segnali e poi lo visualizza di colpo! (menter eseguendo lo stesso codice nel main della classe i punti venivano inseriti ogni 2 secondi [il tempo impiegato dalla funzione getsegnale()])

nell'alro caso invece resta una finestra grigia x 6 secondi e poi mi disegna di colpo il grafico!!!

ho provato anche a lanciare un thread apposta x il grafico ma non cambia niente...secondo voi cosa può essere?

grazie mille!!