B&S: Delete Problem with last row in JTable, getSelectedRow() return wrong row index

[Darya Akbari]

Hi all,

I have a very annoying problem in my MVC design and have no clue at all why it happen.

The problem is as follow:

When I try to delete a row from my JTable it works perfect unless I delete the last row. While for all other row the next row is selected, this is not the case for the last row. Hence when I delete the last row, there is no selected row after.

If someone again click on the Delete button the table.getSelectedRow() method should return -1 as there are no rows selected.

Unfortunately, this is not the case and the method return the last stored selected row say 3 for example . As a consequence the program run into an exception.

To make things a little bit tangible I post a simple JTable test program on a MVC base.

To reproduce the error do the following:

1. Start SimpleJTableTest

2. Select last row in table

3. Click on the Delete button, the selected row index is shown, click OK, the row becomes removed from the view and the model, no other remaining row is selected.

4. Click on the Select button, the selected row index -1 should be presented and that's the problem.

Point 4. is the annoying problem. I don't know why the select row is not -1 .

Any help is welcome :roll: .

Regards,
Darya

Here the code for testing:

import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.table.*;
 

public class SimpleJTableTest {
    public static void main(String[] args) {
        SimpleModel model = new SimpleModel();
        SimpleController contoller = new SimpleController(model);
    }
}
 

interface ModelObserver {
    void updateModel();
}
 

class SimpleView implements ModelObserver {
    private SimpleModel model;
    private SimpleController controller;
 
    JFrame frame;
    JTable jt;
    JScrollPane jsp;
 
    JButton delete;
    JButton select;
 
    JPanel panel;
 
    public SimpleView(SimpleController sc, SimpleModel sm) {
        controller = sc;
        model = sm;
        model.registerObserver((ModelObserver) this);
    }
 
    public void buildGUI() {
        frame = new JFrame("Simple JTable Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        jt = new JTable((AbstractTableModel) model);
        jsp = new JScrollPane(jt);
 
        delete = new JButton("Delete");
        select = new JButton("Select");
        delete.addActionListener(new DeleteListener());
        select.addActionListener(new SelectListener());
 
        panel = new JPanel();
        panel.add(delete);
        panel.add(select);
 
        frame.getContentPane().add(jsp, BorderLayout.CENTER);
        frame.getContentPane().add(panel, BorderLayout.SOUTH);
 
        frame.setSize(300, 200);
        frame.setVisible(true);
    }
 
    public void updateModel() {
        jt.setModel((AbstractTableModel) model);
        jt.updateUI();
    }
 
    class DeleteListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            int selectedRow = jt.getSelectedRow();     
            Object[] options = {"OK"};       
            int option = JOptionPane.showOptionDialog(null,
                    "Selected row " + selectedRow,
                    "Delete Information",
                    JOptionPane.DEFAULT_OPTION,
                    JOptionPane.INFORMATION_MESSAGE,
                    null, options, options[0]);
            if (option == JOptionPane.OK_OPTION) {
                controller.deleteRow(selectedRow);
            }
        }
    }
 
    class SelectListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            int selectedRow = jt.getSelectedRow();            
            Object[] options = {"OK"};       
            int option = JOptionPane.showOptionDialog(null,
                    "Selected row " + selectedRow,
                    "Select Information",
                    JOptionPane.DEFAULT_OPTION,
                    JOptionPane.INFORMATION_MESSAGE,
                    null, options, options[0]);
            if (option == JOptionPane.OK_OPTION) {
                controller.selectRow(selectedRow);
            }
        }
    }
}
 

class SimpleModel extends AbstractTableModel {
    private ArrayList columns;
    private ArrayList rows;
 
    private ArrayList observers = new ArrayList();
 
    public SimpleModel() {
        initialize();
    }
 
    public void initialize() {
        columns = new ArrayList();
        rows = new ArrayList();
 
        String[] rowA = {"a", "a", "a"};
        String[] rowB = {"b", "b", "b"};
        String[] rowC = {"c", "c", "c"};
        String[] rowD = {"d", "d", "d"};
 

 
        rows.add(rowA);
        rows.add(rowB);
        rows.add(rowC);
        rows.add(rowD);
 
        columns.add("Column1");
        columns.add("Column2");
        columns.add("Column3");
    }
 
    public int getColumnCount() {
        return columns.size();
    }
 
    public int getRowCount() {
        return rows.size();
    }
 
    public Object getValueAt(int row, int column) {
        Object[] tableRow = (Object[]) this.rows.get(row);
        return tableRow[column];
    }
 
    public String getColumnName(int column) {
        return columns.get(column).toString();
    }
 
    public int getColumnPosition(String columnName) {
        return columns.indexOf(columnName);
    }
 
    public boolean isCellEditable(int row, int column) {
        return false;
    }
 
    public void setValueAt(Object o, int row, int column) {
        Object[] tableRow = (Object[]) this.rows.get(row);
        tableRow[column] = o;
    }
 
    public void deleteRow(int row) {
        rows.remove(row);
        printRows();
        notifyObservers();
    }
 
    private void printRows() {
        Iterator it = rows.iterator();
        while (it.hasNext()) {
            String[] record = (String[]) it.next();
            for (int j = 0; j < record.length; j++) {
                System.out.print( " | " + record[j]);
            }
            System.out.println();
        }
        System.out.println();
    }
 

    public void selectRow(int row) {
    }
 
    public void registerObserver(ModelObserver observer) {
        observers.add(observer);
    }
 
    public void notifyObservers()  {
        for (int i = 0; i < observers.size(); i++) {
            ModelObserver observer = (ModelObserver)observers.get(i);
            observer.updateModel();
        }
    }
 
}
 

class SimpleController {
    private SimpleModel model;
    private SimpleView view;
 
    public SimpleController(SimpleModel sm) {
        model = sm;
        view = new SimpleView(this, model);
        view.buildGUI();
    }
 
    public void deleteRow(int row) {
        model.deleteRow(row);
    }
 
    public void selectRow(int row) {
        model.selectRow(row);
    }
}

[Anonymous]

Hi Darya,

Did you have any luck with this problem?

Have you tried the following code?

class DeleteListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            int selectedRow = jt.getSelectedRow();     
            Object[] options = {"OK"};       
            int option = JOptionPane.showOptionDialog(null,
                    "Selected row " + selectedRow,
                    "Delete Information",
                    JOptionPane.DEFAULT_OPTION,
                    JOptionPane.INFORMATION_MESSAGE,
                    null, options, options[0]);
            if (option == JOptionPane.OK_OPTION) {
                controller.deleteRow(selectedRow);
jt.clearSelection();
            }
        }
    }  

Notice that I've added a line - jt.clearSelection();, this will clear any selected rows once the row has been deleted. When you perform the select now, -1 is returned.

Cheers,
Matt.

[Darya Akbari]

Hi Matt,

Your jt.clearSelection() unfortunately doesn't help here either.

I have a workaround in my assignment solution, so I can deal with the problem. But honestly I would be more satisfied when we can make this minimized model I've posted run.

Regards,
Darya

[Anonymous]

That's strange cause it worked when I added the line to your code.

[Darya Akbari]

On what system are you testing? I test on Win XP. Did you follow the steps I described?

Regards,
Darya

[Darya Akbari]

Maybe I forgot to say that one must copy all code and paste it in a file named SimpleJTableTest.java.

Regards,
Darya

[Ta Ri Ki Sun]

Originally posted by Matt Garner:
That's strange cause it worked when I added the line to your code.

Tested, it works here too, running win xp atm, let me know if you want me to try in linux

[Mihai Radulescu]

Hi, Darya


I use sometimes the :
ListSelectionModel (each table has one).This model has a method :
removeSelectionInterval(int,int)

I hope this will help.

Regards,
Mihai

[Mihai Radulescu]

I have also table(s) in my gui(s) and after I move/deletete some row(amd I change the model) I do :

private void selectTableRow(int row) {
    if(row >= 0) {
        table.setRowSelectionInterval(row, row);
    }
}

In this way I have control over the row selection.

I hope this will help


Regards,
Mihai.
[ July 11, 2005: Message edited by: Mihai Radulescu ]

[Darya Akbari]

Hi Ta Ri Ki Sun,

what is atm? Nice to see whether it works under linux, however I have the problem under the following java version and operation system:

JAVA VERSION:
-------------

java version "1.4.2_05"


HOST PLATFORM:
--------------

Dell Latitude D800
Intel Pentium M processor 1600MHz
processor speed 1.56 GHz
RAM 1024 MB
Microsoft Windows XP Professional

It's very strange that you do not reproduce the problem as I do

Do you really get a -1

Regards,
Darya

[Ta Ri Ki Sun]

Originally posted by Darya Akbari:
Hi Ta Ri Ki Sun,

what is atm?

At the moment, sorry I assumed

Nice to see whether it works under linux

No it works under windows, but I don't see why it wouldn't work under linux

Here's my version info

C:\SunCerts\SCJD\URLyBird\dist>java -version
java version "1.4.2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2-b28)
Java HotSpot(TM) Client VM (build 1.4.2-b28, mixed mode)

I specifically tested the change Matt suggested, without his line clearSelection I always ended up with the last selection, this way it always goes to -1