What's the best rule for fitting a dynamic JTable inside a dialog or a frame?(height issue)

Question

I want to calculate the height of a dialog that contain only a table depending on how many rows that table it has so I'm using the cross multiplication rule.For example i check initially that my table is well fitting into the dialog(Without space at the bottom) for some value and after that i use the cross multiplication rule because data are dynamic.But unfortunately this rule does not solve the problem.What's the best rule for fitting a dynamic table inside a dialog or a frame? Here is my code

public class FlowLayoutChangingGap {
    public static void main(String[] args) {
        // just for testing perpose but data are getting from database and it's dynamic
        Object[][] data = {
                {"Kathy", "Smith", "Snowboarding", new Integer(5)},
                {"John", "Doe", "Rowing", new Integer(3)},
                {"Sue", "Black", "Knitting", new Integer(2)},
                {"Jane", "White", "Speed reading", new Integer(20)},
                {"Joe", "Brown", "Pool", new Integer(10)}};

        Object[] columnNames = {"firstname", "lastname", "age"};
        final JTable table = new JTable(data, columnNames);
        JFrame aWindow = new JFrame("This is a Test");
        aWindow.setBounds(50, 50, 500, 500);
        aWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        FlowLayout flow = new FlowLayout(FlowLayout.LEFT, 20, 30);
        Container content = aWindow.getContentPane();
        content.setLayout(flow);
        JButton jButton = new JButton("Press Me");
        ActionListener l = new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                JPanel jPanel = new JPanel();
                jPanel.setLayout(new GridBagLayout());
                GridBagConstraints gbc = new GridBagConstraints();
                gbc.anchor = GridBagConstraints.NORTHWEST;
                gbc.fill = GridBagConstraints.BOTH;
                gbc.gridx = 0;
                gbc.gridy = 0;
                gbc.weightx = 1.0;
                gbc.weighty = 1.0;
                jPanel.add(table, gbc);
                JDialog jdialog = new JDialog();
                jdialog.setContentPane(jPanel);

                jdialog.setLocationRelativeTo(null);
                int height = table.getModel().getRowCount() * 25;
                jdialog.setSize(400, height);
                jdialog.setVisible(true);

            }
        };
        jButton.addActionListener(l);
        content.add(jButton);
        aWindow.setVisible(true);
    }
}

Answer 1

Here is a way to fix the number of rows displayed in the scroll-pane.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;

class FlowLayoutChangingGap {

    public static final int ROWS = 3;

    FlowLayoutChangingGap() {
        // just for testing perpose but data are getting from database and it's dynamic
        Object[][] data = {
            {"Kathy", "Smith", "Snowboarding", new Integer(5)},
            {"John", "Doe", "Rowing", new Integer(3)},
            {"Sue", "Black", "Knitting", new Integer(2)},
            {"Jane", "White", "Speed reading", new Integer(20)},
            {"Joe", "Brown", "Pool", new Integer(10)}};
        Object[] columnNames = {"firstname", "lastname", "age"};
        final JTable table = new JTable(data, columnNames) {

            @Override
            public Dimension getPreferredScrollableViewportSize() {
                Dimension d = getPreferredSize();
                // Note: margin is included in rowHeight
                int n = getRowHeight(); // + getRowMargin();
                // tbd: insets? we are one-off here
                return new Dimension(d.width, (n * ROWS));
            }
        };
        JPanel jPanel = new JPanel();
        jPanel.setBorder(new EmptyBorder(6, 6, 6, 6));
        jPanel.setLayout(new GridLayout());
        JScrollPane sp = new JScrollPane(table);
        //sp.getViewport().
        jPanel.add(sp);
        JDialog jdialog = new JDialog();
        jdialog.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        jdialog.setContentPane(jPanel);

        jdialog.setLocationRelativeTo(null);
        jdialog.pack();
        jdialog.setVisible(true);
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                new FlowLayoutChangingGap();
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}