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As you already know, JTabbedPane provides a convenient way for components such as JPanels to share the same real estate on the screen. It also allows a user to select a desired panel by clicking on a tab. If you’ve ever used a Firefox browser than you truly appreciate tabbed panes. Firefox displays each web page in a separate tab, allowing a user to switch between pages by clicking on a corresponding tab.

Up until JDK 1.6, we had limited control of what was rendered on a tab itself. In particular we were limited to the label, the icon and a tooltip. In other words we could not place a button on a tab itself as is done in a Firefox browser. Many improvised by manually drawing components and simulating their behavior. Although this solution worked great, the code was way too complicated for a simple task. With JDK 6 came three new methods which completely changed the behavior of a tabbed pane. You can now set componets on a tab itself. In addition, swing will render these components for you. All possible with three methods below:

public void setTabComponentAt(int index, Component component) – allows you to add a component such as a button to a tab. The rendering and the event handling is done for you by swing.

public Component getTabComponentAt(int index) – gets a component for a corresponding index that was set by a setTabComponentAt(..) method above.

public int indexOfTabComponent(Component tabComponent) – reverse lookup, that returns an index of a tab that corresponds to the tab component set by a setTabComponentAt(..) method above. This is particularly handy if you are using a button to remove a corresponding tab from a tabbed pane.

Below is a simple example that illustrates how to implement a Firefox style close button on the individual tab. Keep in mind this example won’t work on versions prior to JDK 1.6!

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class JtabbedCloseExample extends JFrame {

JTabbedPane jtabbedPane;

class TabButton extends JPanel implements ActionListener {

public TabButton( String label ){

super(new FlowLayout());

add( new JLabel( label ));

JButton button = new JButton(”X”);

button.addActionListener( this );

button.setMargin(new Insets(0,0,0,0));

add( button );

}

public void actionPerformed(ActionEvent ae ){

// close the tab which was clicked
jtabbedPane.remove(jtabbedPane.indexOfTabComponent( this ) );

}

}

public JtabbedCloseExample() {

jtabbedPane = new JTabbedPane();

jtabbedPane.add(new JTextArea(”Tab 1 text area”));

jtabbedPane.add(new JTextArea(”Tab 2 text area”));

jtabbedPane.add(new JTextArea(”Tab 3 text area”));

jtabbedPane.setTabComponentAt( 0, new TabButton(”Tab 1″) );

jtabbedPane.setTabComponentAt( 1, new TabButton(”Tab 2″) );

jtabbedPane.setTabComponentAt( 2, new TabButton(”Tab 3″) );

getContentPane().add( jtabbedPane );

setSize(new Dimension(300, 200));

setVisible(true);

}

public static void main ( String [] args ){

new JtabbedCloseExample();

}

}

This is not the best looking window. However, it clearly illustrates the easy with which you can add your custom components to the tabs!

This entry was posted on Friday, November 16th, 2007 at 2:36 am and is filed under Java. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.