Event Handling between JPanels

Question

Hi everyone,
I'm trying a three-fold assignment on java, which relates to graphs and finding strongly connected components.
In the first part, the user can create his own graph and the program should find all SCC and display them.
In the second part, the program creates random graphs and then finds all SCC and displays them.
In the third part, some statistical data is to be displayed.
So what I have done so far is that I have created a JFrame on which I have added 3 JPanels, each for every part of the assignment.
Changing between the JPanels is done by a JTabbedPane.
My problem lies on the second part. I've created a class called RandomGraphPanel, which extends JPanel. Then I've created two sub-JPanels,
called RandomGraphAreaPanel, where the graph should be displayed and RandomGraphDataPanel, where the user can choose some parameters on which the random graph is based. I don't know how I can paint the graph on the first sub-JPanel, after pressing a button on the second sub-JPanel.
I will include some code from my classes:
public class RandomGraphPanel extends JPanel
     private JPanel graphArea;
     private RandomGraphDataPanel data;
     private RandomGraphAreaPanel area;
     public RandomGraphPanel()
          super();
          setLayout(new BorderLayout(5,5));
          data = new RandomGraphDataPanel();
          area = new RandomGraphAreaPanel();
          add(data, BorderLayout.SOUTH);
          add(area, BorderLayout.CENTER);          
     }//RandomGraphPanel constructor
}//RandomGraphPanel class
public class RandomGraphDataPanel extends JPanel
     public RandomGraphDataPanel()
          super();
          //part where RandomGraphDataPanel is filled with 2 JSliders and 1 JButton
     }//RandomGraphDataPanel constructor
     private class ButtonHandler implements ActionListener
          public void actionPerformed(ActionEvent event)
               //code that is executed when the button is pressed               
          }//actionPerformed
     }//ButtonHandler private class
}//RandomGraphDataPanel classAny help will be appreciated.
Thanks,
philimonas

Answer 1

Probably the best way would be to somehow implement the MVC pattern here. Another way would be to move the button handling code out of the RandomGraphDataPanel class and into the RandomGraphPanel class. You could then pass the ActionListener into the RandomGraphDataPanel object by perhaps a constructor parameter, or by a separate addActionListener method that you have created. Something like so:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
public class RandomGraphPanel extends JPanel
    private JPanel graphArea;
    private RandomGraphDataPanel data;
    private RandomGraphAreaPanel area;
    public RandomGraphPanel()
        super();
        setLayout(new BorderLayout(5, 5));
        // *** passing ActionListener to the data class via constructor parameter
        data = new RandomGraphDataPanel(new ButtonHandler());
        area = new RandomGraphAreaPanel();
        add(data, BorderLayout.SOUTH);
        add(area, BorderLayout.CENTER);    
    // *** move this code into this class
    private class ButtonHandler implements ActionListener
        public void actionPerformed(ActionEvent event)
            area.showGraph();  // or whatever is needed to show graph       
}and
//import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
public class RandomGraphDataPanel extends JPanel
    public RandomGraphDataPanel(ActionListener buttonHandler)
        super();
        JButton someButton = new JButton("Show Graph");
        someButton.addActionListener(buttonHandler);
    private class ButtonHandler implements ActionListener
        public void actionPerformed(ActionEvent event)
            //code that is executed when the button is pressed         
}