Learning Java

The JTabbedPane Class

If you’ve ever dealt with the System control panel in Windows, you already know what a JTabbedPane is. It’s a container with labeled tabs. When you click on a tab, a new set of controls is shown in the body of the JTabbedPane. In Swing, JTabbedPane is simply a specialized container.

Each tab has a name. To add a tab to the JTabbedPane , simply call addTab( ). You’ll need to specify the name of the tab as well as a component that supplies the tab’s contents. Typically, it’s a container holding other components.

Even though the JTabbedPane only shows one set of components at a time, be aware that all the components on all the pages are in memory at one time. If you have components that hog processor time or memory, try to put them into some “sleep” state when they are not showing.

The following example shows how to create a JTabbedPane. It adds standard Swing components to a first tab, named Controls . The second tab is filled with an instance of ImageComponent , which was presented earlier in this chapter.

//file: TabbedPaneFrame.java
import java.awt.*; 
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;

public class TabbedPaneFrame {
  public static void main(String[] args) {
    // create a JFrame to hold everything
    JFrame f = new JFrame("TabbedPaneFrame");
    f.addWindowListener(new WindowAdapter( ) {
      public void windowClosing(WindowEvent we) { System.exit(0); }
    });
    f.setSize(200, 200);
    f.setLocation(200, 200);

    JTabbedPane tabby = new JTabbedPane( );
    
    // create a controls pane
    JPanel controls = new JPanel( );
    controls.add(new JLabel("Service:"));
    JList list = new JList(
        new String[] { "Web server", "FTP server" });
    list.setBorder(BorderFactory.createEtchedBorder( ));
    controls.add(list);
    controls.add(new JButton("Start"));
    
    // create an image pane
    String filename = "Piazza di Spagna.jpg";
    Image image = Toolkit.getDefaultToolkit( ).getImage(filename);
    JComponent picture = new JScrollPane(new ImageComponent(image));
    
    tabby.addTab("Controls", controls);
    tabby.addTab("Picture", picture);
    
    f.getContentPane( ).add(tabby);
    f.setVisible(true);
  }
}

The code is not especially fancy, but the result is an impressive-looking user interface. The first tab is a JPanel that contains some other components, including a JList with an etched border. The second tab simply contains an ImageComponent wrapped in a JScrollPane. The running example is shown in Figure 14.8.

Figure 14-8. Using a tabbed pane