Detecting Row Changes on a JTable

[Riaan Nel]

Good Morning Everybody

I have a scenario where I have a JTable in which the user is allowed to make changes. When the user changes the selected row, I would like to pop up a confirmation prompt before saving any changes to a row. I've tried a ListSelectionListener, but it causes the UI to be 'frozen' between two selected rows when the prompt comes up. Is there any way in which I can get a listener on a JTable to fire before the row is actually changed? I posted this in the General Java forum (https://coderanch.com/t/535665/java/java/Detecting-Row-Changes-JTable) as well, as I did not realize that JavaRanch has a Swing/AWT/SWT/JFace forum.

Here's a simplified example.

import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTable;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
public class Main {
public static void main(String[] args) {
JFrame testFrame = new JFrame("JTable Test");
testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
testFrame.setSize(640, 480);
testFrame.setLayout(new GridLayout(1, 1));
Object[] columns = {"Name", "Surname"};
Object[][] data = {{"Mickey", "Mouse"}, {"Donald", "Duck"}, {"Elmer", "Fudd"}};
final JTable testTable = new JTable(data, columns);
testTable.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e) {
//I want something to happen before the row change is triggered on the UI.
JOptionPane.showMessageDialog(testTable, "Row changed!");
}
});
testTable.changeSelection(0, 0, false, false);
testFrame.add(testTable);
testFrame.setVisible(true);
}
} 

Thanks for your help!

[Darryl Burke]

 

Riaan Nel wrote:I posted this in the General Java forum (https://coderanch.com/t/535665/java/java/Detecting-Row-Changes-JTable) as well, as I did not realize that JavaRanch has a Swing/AWT/SWT/JFace forum.

Thanks for linking the duplicate thread. I've removed it.

[Darryl Burke]

Here's my attempt to solve your problem with a class extending JTable and overriding valueChanged().

import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
public class RowVerifierTableTest {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new RowVerifierTableTest().makeUI();
}
});
}
public void makeUI() {
int rows = 30;
int columns = 5;
final JTable table = new RowVerifierTable(rows, columns);
for (int row = 0; row < rows; row++) {
for (int column = 0; column < columns; column++) {
table.setValueAt(row + 100 * column, row, column);
}
}
final JFrame frame = new JFrame();
frame.add(new JScrollPane(table));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
class RowVerifierTable extends JTable {
boolean rowSelectionAdjusting2;
int selectedRow = -1;
public RowVerifierTable(int rows, int columns) {
super(rows, columns);
setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
}
@Override
public void valueChanged(ListSelectionEvent e) {
int approve = JOptionPane.YES_OPTION;
if (!e.getValueIsAdjusting()) {
if (selectedRow != -1) {
approve = JOptionPane.showConfirmDialog(null,
"Change row selection?", "Confirm",
JOptionPane.YES_NO_OPTION);
}
if (approve == JOptionPane.YES_OPTION) {
super.valueChanged(e);
} else {
getSelectionModel().removeListSelectionListener(this);
getSelectionModel().clearSelection();
setRowSelectionInterval(selectedRow, selectedRow);
getSelectionModel().addListSelectionListener(this);
scrollRectToVisible(getCellRect(selectedRow, 0, true));
repaint();
}
selectedRow = getSelectedRow();
}
}
}

I can't see any LaF independent way to prevent the clicked cell from appearing selected before the dialog is shown.

[Hauke Ingmar Schmidt]

Please have a look in the Oracle's JTable tutorial and how to use models. You need a model that just doesn't change if it shouldn't. No need to tamper with the presentation.

[Riaan Nel]

Hi Guys

Darryl, thank you for your solution - I'll play with it a bit when I get back to working on the app.

Hauke, thanks for the link and the hint, I'll go through it and see if I can get my table model to behave the way I want.

Regards,
Riaan

[Riaan Nel]

For future reference, here's the solution that I came up with.

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTable;
import javax.swing.KeyStroke;
import javax.swing.ListSelectionModel;
public class Main {
public static void main(String[] args) {
JFrame testFrame = new JFrame("JTable Test");
testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
testFrame.setSize(640, 480);
testFrame.setLayout(new GridLayout(1, 1));
Object[] columns = {"Name", "Surname"};
Object[][] data = {{"Mickey", "Mouse"}, {"Donald", "Duck"}, {"Elmer", "Fudd"}};
final JTable testTable = new JTable(data, columns);
InputMap inputMap = testTable.getInputMap();
inputMap.put(KeyStroke.getKeyStroke("DOWN"), "DOWN");
inputMap.put(KeyStroke.getKeyStroke("UP"), "UP");
ActionMap actionMap = testTable.getActionMap();
actionMap.put("DOWN", new AbstractAction() {
public void actionPerformed(ActionEvent e) {
JOptionPane.showMessageDialog(null, "Changing Row!");
if (testTable.getSelectedRow() < testTable.getRowCount() - 1) {
testTable.changeSelection(testTable.getSelectedRow() + 1, 0, false, false);
}
}
});
actionMap.put("UP", new AbstractAction() {
public void actionPerformed(ActionEvent e) {
JOptionPane.showMessageDialog(null, "Changing Row!");
if (testTable.getSelectedRow() > 0) {
testTable.changeSelection(testTable.getSelectedRow() - 1, 0, false, false);
}
}
});
System.out.println(testTable.getMouseListeners());
for (MouseListener listener : testTable.getMouseListeners()) {
testTable.removeMouseListener(listener);
}
testTable.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
for (MouseMotionListener listener : testTable.getMouseMotionListeners()) {
testTable.removeMouseMotionListener(listener);
}
testTable.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
JTable table = (JTable)e.getSource();
int rowAtPoint = table.rowAtPoint(e.getPoint());
int columnAtPoint = table.columnAtPoint(e.getPoint());
if (rowAtPoint != -1 && rowAtPoint != testTable.getSelectedRow()) {
JOptionPane.showMessageDialog(null, "Changing Row!");
table.changeSelection(rowAtPoint, columnAtPoint, false, false);
}
}
});
testTable.changeSelection(0, 0, false, false);
testFrame.add(testTable);
testFrame.setVisible(true);
}
}