Question

I’m using a JTabbedPane in my application and I listen to its changes with ChangeListener so that I can know which tab is currently selected.
So my stateChanged method is;

public void stateChanged(ChangeEvent e) {
    currentPageIndex = jTabbedPane.getSelectedIndex();
}

But while I’m adding new tabs to the JTabbedPane it throws an ArrayIndexOutOfBoundsException in the method above, I don’t know why. Some suggested for a similar case that this is a bug https://bugs.java.com/bugdatabase/view_bug?bug_id=4873983, but as you’ll see some says the solution is to work with Swing from EventDispatchThread.

What does it mean, do they mean the SwingUtilities.invokeLater thing? Can someone show me how I can modify my stateChanged method accordingly to avoid the exception?

Edit: And below is my addTab() method. This is called multiple times at the beginning of the program, and it ‘sometimes’ fires stateChanged() method. And at some point stateChanged() causes the exception. That’s what I could tell from the debugger up to now. I know it doesn’t seem clear, so if you haven’t already heard this kind of thing before, that’s OK, thanks for your effort. But I think this could be related to the link I gave above.

void addTab(EJournal eJournalModel,int index, String pageName) {
    SectionPage newPage = new SectionPage(jTabbedPane.getSize(), controller, eJournalModel.getSections().get(currentPageIndex));
    JScrollPane scrollPane = new JScrollPane(newPage);
    scrollPanes.add(index, scrollPane);
    sectionPages.add(index, newPage);
    jTabbedPane.insertTab(pageName, idleIcon, scrollPane, null, index);
    jTabbedPane.updateUI();
}

Edit2 : This exception is thrown. After my methods actually finished executing and evertying is finished, an actionPerformed() is fired, then a whole bunch of stuff and then exception.

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0
        at javax.swing.plaf.basic.BasicTabbedPaneUI.tabForCoordinate(BasicTabbedPaneUI.java:1488)
        at javax.swing.plaf.basic.BasicTabbedPaneUI.setRolloverTab(BasicTabbedPaneUI.java:558)
        at javax.swing.plaf.basic.BasicTabbedPaneUI.access$2000(BasicTabbedPaneUI.java:37)
        at javax.swing.plaf.basic.BasicTabbedPaneUI$Handler.mouseEntered(BasicTabbedPaneUI.java:3604)
        at java.awt.Component.processMouseEvent(Component.java:6272)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3255)
        at java.awt.Component.processEvent(Component.java:6028)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4630)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4574)
        at java.awt.LightweightDispatcher.trackMouseEnterExit(Container.java:4363)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4220)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
        at java.awt.Container.dispatchEventImpl(Container.java:2085)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

Answer 1

You did not post a SSCCE. 5 lines of code is NOT a SSCCE.

For one thing you should NOT be using the updateUI() method. I have no idea why I see this so often in posted code.