In this example you will learn how to detect tab selection changes in a JTabbedPane component. To get notified when a tab is selected you must add a ChangeListener to the JTabbedPane component using the addChangeListener(). This method take an instance of class that implements the ChangeListener interface as its arguments.

In this example we implement the ChangeListener interface in the TabbedPaneSelection class. And we need to create an implementation for the stateChanged() method as defined by this interface contract. By implementing the interface in the TabbedPaneSelection class, we don’t need to create a separate class that specifically implement this interface. That’s why in the code snippet below we just pass the current object, using the this keyword, when calling the addChangeListener() method.

The stateChanged() method of this interface will be fired every time a new tab is selected. To get the selected tab index you can use the JTabbedPane‘s getSelectedIndex() method. The index returned by the getSelectedIndex() method is zero based, it means that if you select the first tab you will get index of 0, and if you select the second tab you will get index of 1.

package org.kodejava.swing;

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.*;

public class TabbedPaneSelection extends JPanel implements ChangeListener {
    public TabbedPaneSelection() {
        initializeUI();
    }

    public static void showFrame() {
        JPanel panel = new TabbedPaneSelection();
        panel.setOpaque(true);

        JFrame frame = new JFrame("JTabbedPane Selection Demo");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(TabbedPaneSelection::showFrame);
    }

    private void initializeUI() {
        JTabbedPane tabbedPane = new JTabbedPane();

        JPanel dashboardPanel = new JPanel();
        tabbedPane.addTab("Dashboard", dashboardPanel);

        JPanel accountPanel = new JPanel();
        tabbedPane.addTab("Account", accountPanel);

        this.setLayout(new BorderLayout());
        this.setPreferredSize(new Dimension(500, 200));
        this.add(tabbedPane, BorderLayout.CENTER);

        // Add ChangeListener to the tabbed pane.
        tabbedPane.addChangeListener(this);
    }

    public void stateChanged(ChangeEvent e) {
        JTabbedPane tabbedPane = (JTabbedPane) e.getSource();
        int selectedIndex = tabbedPane.getSelectedIndex();
        JOptionPane.showMessageDialog(null, "Selected Index: " + selectedIndex);
    }
}

If you run the presented code snippet above you’ll get the output as shown in the image below. And if you click the tab a message dialog will be displayed showing you the selected index.

In this example you will learn how to use JTabbedPane to arrange some components in tabbed view. The JTabbedPane component of the Swing API allows some components such as panels to share the same view. By selecting the corresponding tab, the panel will be displayed on the user’s screen. To add tabs to the JTabbedPane class you can use the addTab() method.

To the addTab() method accept two arguments, the title of the tab and the component you wish to display as the content of the tab. In the code snippet below we will use a simple panel as the content of the tab. You can also define an image icon for the tab which makes the program looks better. You can read it in this example:

Now, let’s create a simple example of JTabbedPane which has three tabs and the corresponding content, they are the Dashboard, Transaction and Account tabs. Below is an image that show how the screen will look.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;

public class SimpleTabbedPane extends JPanel {
    public SimpleTabbedPane() {
        initializeUI();
    }

    public static void showFrame() {
        JPanel panel = new SimpleTabbedPane();
        panel.setOpaque(true);

        JFrame frame = new JFrame("Simple Tabbed Pane Demo");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(SimpleTabbedPane::showFrame);
    }

    private void initializeUI() {
        JTabbedPane tabbedPane = new JTabbedPane();

        JPanel dashboardPanel = new JPanel();
        dashboardPanel.add(new JLabel("Dashboard"));

        // Add Dashboard Tab
        tabbedPane.addTab("Dashboard", dashboardPanel);

        JPanel transactionPanel = new JPanel();
        transactionPanel.add(new JLabel("Transaction"));

        // Add Transactions Tab
        tabbedPane.addTab("Transaction", transactionPanel);

        JPanel accountPanel = new JPanel();
        accountPanel.add(new JLabel("Account"));

        // Add Account Tab
        tabbedPane.addTab("Account", accountPanel);

        this.setLayout(new BorderLayout());
        this.setPreferredSize(new Dimension(500, 200));
        this.add(tabbedPane, BorderLayout.CENTER);
    }
}