Subclassing JTable

[henri henri]

I wanted to subclass JTable to use in my application. The Table works correctly, but I want to add Event functionality. I tried to add the line
this.addTableModelListener(); to this class but it gave a compiler erro. I tried to add the same line to my JFrame clas used to display the instantiated JTable and it did not work.

          model = new BeanTableModel();
          table = new Table(model);
          table.addTableModelListener(this);

 
    import javax.swing.table.*;
    import javax.swing.*;
    import java.awt.Color;
    import java.awt.Font;
    import static film_titles.Colour.*;
    import javax.swing.event.TableModelListener;
 

public class Table extends JTable implements TableModelListener {
      public Table(TableModel tm) {
        super(tm);
 
        this.setForeground(RED);
        this.setFont(new Font("Dialog", Font.PLAIN, 14));
        this.setSelectionForeground(Color.WHITE);
        this.setSelectionBackground(BLUE);
        this.setGridColor(Color.GRAY);
        this.setRowSelectionAllowed(true);
        this.setCellSelectionEnabled(true);
        this.setRowHeight(20);
        this.setShowGrid(true);
 
     /////////   this.addTableModelListener();    /////////
     
     
        TableColumnModel cm = this.getColumnModel();
cm.getColumn(0).setPreferredWidth(245);
cm.getColumn(1).setPreferredWidth(100);
cm.getColumn(2).setPreferredWidth(125);
cm.getColumn(3).setPreferredWidth(40);
        cm.getColumn(4).setPreferredWidth(30);
        cm.getColumn(5).setPreferredWidth(25);
       }
    }

[Ernest Friedman-Hill]

Moving to our Swing/AWT/JFace/SWT forum.

[Jeff Albertson]

Inside your constructor you would write

addTableModelListener(this); 
//or
this.addTableModelListener(this); 

Elsehere you would write

table.addTableModelListener(table);

That being said, your design looks bad. First, do you *really* need to subclass JTable?
What JTable method are you overriding? Second, this sort of typing is bad:

public class Table extends JTable implements TableModelListener 

because one can do the following with it:

JTable table1 = ...
Table table2 = ...
table1.addTableModelListener(table2);

Did you really intend to have one table listen to another? I suspect you wanted
to define a table that needed, solely as an implementation detail, to define a TableModelListener.
In that case, I would define a seperate class implementing TableModelListener, or
if you really need it to access implementation details of Table, to do this:

//Still not keen on subclassing JTable if you don't need to!
public class Table extends JTable {
    private TableModelListener tml = new TableModelListener() {
        public void tableChanged(TableModelEvent e){...}
    };
    
    public Table(...) {
        super(...);
        addTableModelListener(tml);
        ...
    }
}

[ November 02, 2005: Message edited by: Jeff Albrechtsen ]

[henri henri]

I made a subclass of JTable to take some of the design code out of my JInternalFrame class which displays the Table. Thanks for all of your suggestions.

[henri henri]

I tried your suggestion in my code, and none of it works as you suggested.

[Jeff Albertson]

Then you're doing it wrong:

import javax.swing.*;
import javax.swing.event.*;
 
public class ExampleListener implements TableModelListener {
    public void tableChanged(TableModelEvent e) {
        System.out.println("column=" + e.getColumn() + " firstRow=" + e.getFirstRow()
        + " lastRow=" + e.getLastRow() + " type=" + e.getType());
    }
 
    public static void main(String[] args) {
        JTable table = new JTable(16,4);
        table.getModel().addTableModelListener(new ExampleListener());
 
        final JFrame f = new JFrame("ExampleListener");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(table));
        f.pack();
        SwingUtilities.invokeLater(new Runnable(){
            public void run() {
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
}

[henri henri]

Thanks, I will give it a try. I would simply like to be able to re-edit the JavaBean values in my JTable and have those values be transmitted back to the JavaBean via the set methods i have designed in my FilmBean class.

Thanks for your advice on subclassing. it seems that it is not a good idea to do it if one can avoid it.

I have about 60 lines of code in my JTable subclass. it seemed to make sense to keep it in a separate class and instantiate it in the class that will display it like so Table table = new Table(model);
All of the configuration is taken care of in the subclass. Apparently alot of java people are dead set against this approach. I don't have enough experience to understand it or grasp why..