Get value from a cell in JTable

Question

I've looked everywhere but can't seem to figure this out. I just want to pull out a cell's value from my JTable when a user clicks on it.

However at the moment I am getting -1 so I suppose double clicking results in no row being detected. Here is the code:

import java.awt.*;
import java.awt.event.*;
import java.sql.SQLException;
import javax.swing.*;
import javax.swing.table.TableColumn;

public class CardLayoutExample {
    private static JScrollPane scrollPane;

  public static void main(String[] arguments) throws SQLException {

    // main window
    JFrame.setDefaultLookAndFeelDecorated(true);
    JFrame window = new JFrame("CardLayout Example");
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setSize(1500,800); 
    window.getContentPane().setLayout(new BorderLayout());



final CardLayout cardLayout = new CardLayout(); 
final JPanel cardPanel = new JPanel(cardLayout);

JPanel card3 = new JPanel();
cardPanel.add(card3,"All Patients");

String AllPatients="select * from tblPtDetails";
    JTable tablePatientDt = new   JTable(Bquery.buildTableModel(Bquery.resultQuery(AllPatients)));
    tablePatientDt.setEnabled(false);
    tablePatientDt.setPreferredScrollableViewportSize(new Dimension(1200, 400));
    tablePatientDt.setAutoResizeMode( JTable.AUTO_RESIZE_OFF ); 
    tablePatientDt.setRowHeight(30);
    tablePatientDt.setAutoCreateRowSorter(true);
    card3.add(tablePatientDt);
    card3.add(new JScrollPane(tablePatientDt), BorderLayout.CENTER);
    for (int i = 0; i < (tablePatientDt.getColumnCount()); i++) {
        TableColumn columnPatients = null;
        columnPatients = tablePatientDt.getColumnModel().getColumn(i);
        columnPatients.setPreferredWidth(70); //sport column is bigger

    }
    tablePatientDt.addMouseListener(new MouseAdapter() {
           public void mouseClicked(MouseEvent e) {
              if (e.getClickCount() == 2) {
                 int row = tablePatientDt.getSelectedRow();
                 int column = tablePatientDt.getSelectedColumn();
                 //Object val= tablePatientDt.getModel().getValueAt(row, column);
                 //tablePatientDt.getModel().getValueAt(row, column);
                 //return tablePatientDt.getModel().getValueAt(row, column);
                 System.out.println(row);
                 JFrame newFrame = new JFrame();
                 newFrame.setTitle("Detail Screen");
                 newFrame.setVisible(true);
                 }
           }
        });

Answer 1

Your main problem is here:

tablePatientDt.setEnabled(false);

Because the table is not enabled, no cell or row can ever be selected, and so the selected row will always be -1. Solution: get rid of that line. Instead, if you don't want a cell to be editable on double click, override the JTable or its model and override the isCellEditable method:

e.g.,

// create your JTable model here:
DefaultTableModel model = ......

JTable tablePatientDt = new JTable(model){
@Override
public boolean isCellEditable(int row, int column) {
    return false;
}

Other issues: don't add the JTable to more than one component as you're doing. That spells great risk for trouble since Swing components can be added to only one component at a time.

A side recommendation: in your future questions post only small compilable and runnable programs. Your code above cannot run since it has database dependencies that we don't have access to, and is also incomplete. In order to find your problem, I had to take your code and create a small runnable program with it, an mcve (please read the link):

import java.awt.*;
import java.awt.event.*;
import java.sql.SQLException;

import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableColumn;

public class CardLayoutExample {
    private static JScrollPane scrollPane;

    public static void main(String[] arguments) throws SQLException {

        // main window
        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame window = new JFrame("CardLayout Example");
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // !! window.setSize(1500, 800);
        window.getContentPane().setLayout(new BorderLayout());

        final CardLayout cardLayout = new CardLayout();
        final JPanel cardPanel = new JPanel(cardLayout);

        JPanel card3 = new JPanel();
        cardPanel.add(card3, "All Patients");

        String AllPatients = "select * from tblPtDetails";

        //!!  
        String[][] data = {{"1", "2", "3"}, {"4", "5", "6"}, {"7", "8", "9"}};
        String[] columnNames = {"One", "Two", "Three"};
        DefaultTableModel model = new DefaultTableModel(data, columnNames);
        // !! JTable tablePatientDt = new JTable(Bquery.buildTableModel(Bquery.resultQuery(AllPatients)));
        JTable tablePatientDt = new JTable(model){
            @Override
            public boolean isCellEditable(int row, int column) {
                return false;
            }
        };

        // !! tablePatientDt.setEnabled(false);
        tablePatientDt.setPreferredScrollableViewportSize(new Dimension(1200, 400));
        tablePatientDt.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
        tablePatientDt.setRowHeight(30);
        tablePatientDt.setAutoCreateRowSorter(true);
        // !! card3.add(tablePatientDt);
        card3.add(new JScrollPane(tablePatientDt), BorderLayout.CENTER);
        for (int i = 0; i < (tablePatientDt.getColumnCount()); i++) {
            TableColumn columnPatients = null;
            columnPatients = tablePatientDt.getColumnModel().getColumn(i);
            columnPatients.setPreferredWidth(70); // sport column is bigger

        }
        tablePatientDt.addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent e) {
                if (e.getClickCount() == 2) {
                    int row = tablePatientDt.getSelectedRow();
                    int column = tablePatientDt.getSelectedColumn();
                    // Object val= tablePatientDt.getModel().getValueAt(row,
                    // column);
                    // tablePatientDt.getModel().getValueAt(row, column);
                    // return tablePatientDt.getModel().getValueAt(row, column);
                    System.out.println(row);
                    JFrame newFrame = new JFrame();
                    newFrame.setTitle("Detail Screen");
                    newFrame.setVisible(true);
                }
            }
        });

        //!! 
        window.add(cardPanel);
        window.pack();
        window.setVisible(true);
    }
}

But really this effort should be yours not mine, since we're all volunteers, and you're the one asking for volunteer help in solving a problem. So in the future we ask that you create your own mcve to go with your questions.

Also that detail window shouldn't be a JFrame but rather a JDialog.