How to make JTabbedPane Title component take up entire tab width?

Question

Starting with JDK 1.6, JTabbedPane has been enhanced to allow you to specify an arbitrary Component for the title of a tab (I think before, you could only specify a JLabel and/or icon). We make use of this in our application by specifying a Panel with a GridBagLayout and three children: an Icon (on the left), a label (middle), and a close button (right). the middle component, the label, gets all the weightx and has fill set to HORIZONTAL. Everything looks good - as long as the tabs stay on a single row. When another tab is added and the TabbedPane extends to a second row, things don't look: the tabs are allocated alot more white space now - but the Component isn't being given that extra space! Consequently, the icons on the left and right of my label stay next to the label, instead of staying next to the edges of the tab!
Is this a bug in the JDK?
If it's not a bug, how do I make use of all available tab space?

Answer 1

Hi Darryl,
Thanks for the suggestion. Below is a primitive standalone example. It brings up an empty frame and you can click on the "Add Tab" button to add a tab. When you do, you'll see that the tab's "title" area consists of an "i" button, a label, and a "x" button. The tab itself isn't much bigger than those three components, so things look ok. Now, add two more tabs....the 2nd tab still fits on the first row of the TabbedPane, so things still look ok. When you add the third tab, the first tab gets placed on a new 2nd row of the TabbedPane and the tab takes up the whole width of the TabbedPane....but the "i" and the "x" buttons are still scrunched up next to the label - rather than near the edges of the tab, where they would be expected.
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class TabExample extends javax.swing.JFrame {
    public TabExample() {
        initComponents();
     class TabRenderer extends JPanel {
          private JButton infoButton;
          private JLabel label;
          private JButton closeButton;
          public TabRenderer(String title) {
               infoButton = new JButton("i");
               label = new JLabel(title);
               closeButton = new JButton("x");
               setLayout(new GridBagLayout());
               GridBagConstraints gc = new GridBagConstraints();
               gc.gridy = 0;
               gc.gridx = 0;
               gc.anchor = GridBagConstraints.WEST;
               gc.fill = GridBagConstraints.NONE;
               gc.weightx = 0;
               this.add(infoButton, gc);
               gc.gridx = 1;
               gc.anchor = GridBagConstraints.WEST;
               gc.fill = GridBagConstraints.HORIZONTAL;
               gc.weightx = 1.0;
               this.add(label, gc);
               gc.gridx = 2;
               gc.anchor = GridBagConstraints.EAST;
               gc.fill = GridBagConstraints.NONE;
               gc.weightx = 0;
               this.add(closeButton, gc);
    private void initComponents() {
        tabbedPane = new javax.swing.JTabbedPane();
        jButton1 = new javax.swing.JButton();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().add(tabbedPane, java.awt.BorderLayout.CENTER);
        jButton1.setText("Add Tab");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                addTabHandler(evt);
        getContentPane().add(jButton1, java.awt.BorderLayout.SOUTH);
        pack();
     private void addTabHandler(java.awt.event.ActionEvent evt) {
          int index = tabbedPane.getTabCount();
          tabbedPane.add(new JPanel(), index);
          tabbedPane.setTabComponentAt(index, new TabRenderer("Tab " + index));
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame f = new TabExample();
                    f.setSize(400, 300);
                    f.setVisible(true);
    private javax.swing.JButton jButton1;
    private javax.swing.JTabbedPane tabbedPane;
}