Java-将选项卡添加到JTabbedPane导致StackOverflowError（禁用触发ChangeEvent？）

Question

Hey StackOverflow community, I'm having a StackOverflow problem.

I'm having difficulty adding a new tab to my GUI's JTabbedPane container, when the [+] tab is selected. So far, whenever I click the [+] tab, new tabs are appended until a StackOverflowError occurs.

A new tab is added to the JTabbedPane when the following condition is true.

if(songPanel.getSelectedIndex()==songPanel.getTabCount()-1){
...
}

I've tried to revert back to the previously selected tab to avoid tabs being added repeatedly to the JTabbedPane, to no avail. When the ChangeEvent actuator is fired, does it stay on indefinitely? I haven't come across anything useful in the SE7 API.

Relevant code (non-compilable, excerpt from larger program. May be missing brackets, only because I copy-pasted excerpts of the code, and liable to make mistakes)

@Override
    public void init(){
        setLayout(new GridLayout(MAIN_LAYOUT_ROWS, MAIN_LAYOUT_COLUMNS));
        add(renderPanel = new JScrollPane());
        add(controlPanel = new JPanel());
        add(colourPanel = new JPanel());
        add(songPanel = new JTabbedPane());

        //songPanel options
        songPanel = new JTabbedPane();
        songPanel.setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);
        songPanel.addTab("#1", new JTextArea());
        songPanel.addTab("+", null, new JLabel(), "+");

        Container cp = getContentPane();
        cp.add(BorderLayout.SOUTH, songPanel);

        //integrate songPanel changeListener 
        songPanel.addChangeListener(new ChangeListener(){

            @Override //Method called when selected tab changes
            public void stateChanged(ChangeEvent e){
                try {          
                    if(songPanel.getSelectedIndex()==songPanel.getTabCount()-1){
                        addTab("songPanel");
                    }
                } catch (StackOverflowError soe){soe.printStackTrace();}
            }
        });
//*************************************************************************
    @Override
    public void start(){

    }
//*************************************************************************
    private void addTab(String panelName){
        System.out.println("ADDING TAB");
        if(panelName.equals("songPanel")){
            String tabName = ("#" + Integer.toString(songPanel.getTabCount()-1));
            songPanel.insertTab(tabName, null, new JTextField(), tabName,           songPanel.getTabCount()-2);
        }
    }
}
//**************************************************************************
}

I've tried:

• Setting a revert index in the addTab() method, so the newest tab is selected (still results in StackOverflowError)

Note this line:

songPanel.getSelectedIndex()==songPanel.getTabCount()-1)

Both "songPanel.getSelectedIndex()" and "songPanel.getTabCount()-1)" are always equal, so condition is always true ( causing the StackOverflowError )

Error message:

java.lang.StackOverflowError
at javax.swing.text.StyleContext$SmallAttributeSet.getAttributeNames(StyleContext.java:947)
at javax.swing.text.StyleContext$SmallAttributeSet.containsAttributes(StyleContext.java:973)
at javax.swing.text.StyleContext$SmallAttributeSet.equals(StyleContext.java:852)
at java.util.WeakHashMap.eq(WeakHashMap.java:282)
at java.util.WeakHashMap.get(WeakHashMap.java:379)
at java.util.Collections$SynchronizedMap.get(Collections.java:2031)
at javax.swing.text.StyleContext.getImmutableUniqueSet(StyleContext.java:520)
at javax.swing.text.StyleContext.addAttributes(StyleContext.java:340)
at javax.swing.text.AbstractDocument$AbstractElement.addAttributes(AbstractDocument.java:1985)
at javax.swing.text.AbstractDocument$AbstractElement.<init>(AbstractDocument.java:1777)
at javax.swing.text.AbstractDocument$LeafElement.<init>(AbstractDocument.java:2502)
at javax.swing.text.AbstractDocument$BidiElement.<init>(AbstractDocument.java:2674)
at javax.swing.text.AbstractDocument.<init>(AbstractDocument.java:149)
at javax.swing.text.AbstractDocument.<init>(AbstractDocument.java:109)
at javax.swing.text.PlainDocument.<init>(PlainDocument.java:90)
at javax.swing.text.PlainDocument.<init>(PlainDocument.java:80)
at javax.swing.text.DefaultEditorKit.createDefaultDocument(DefaultEditorKit.java:130)
at javax.swing.plaf.basic.BasicTextUI.installUI(BasicTextUI.java:799)
at javax.swing.JComponent.setUI(JComponent.java:655)
at javax.swing.text.JTextComponent.setUI(JTextComponent.java:338)
at javax.swing.text.JTextComponent.updateUI(JTextComponent.java:348)
at javax.swing.text.JTextComponent.<init>(JTextComponent.java:322)
at javax.swing.JTextField.<init>(JTextField.java:231)
at javax.swing.JTextField.<init>(JTextField.java:172)
at application.Analyzer.addTab(Analyzer.java:133)
at application.Analyzer.access$100(Analyzer.java:24)
at application.Analyzer$1.stateChanged(Analyzer.java:101)
at javax.swing.JTabbedPane.fireStateChanged(JTabbedPane.java:416)
at javax.swing.JTabbedPane$ModelListener.stateChanged(JTabbedPane.java:270)
at javax.swing.DefaultSingleSelectionModel.fireStateChanged(DefaultSingleSelectionModel.java:132)
at javax.swing.DefaultSingleSelectionModel.setSelectedIndex(DefaultSingleSelectionModel.java:67)
at javax.swing.JTabbedPane.setSelectedIndexImpl(JTabbedPane.java:616)
at javax.swing.JTabbedPane.insertTab(JTabbedPane.java:735)
at application.Analyzer.addTab(Analyzer.java:133)
at application.Analyzer.access$100(Analyzer.java:24)
.
.
.

Do you have any suggestions? I know it's kind of vague, but I'm really not sure what is going wrong.

Any suggestions? Thanks. Tyler

Answer 1

StackOverflow identifies an infinite recursion. So first thing is to find that recursion. In your case these are the lines of the stacktrace that identifies that recursion:

at application.Analyzer.addTab(Analyzer.java:133) at application.Analyzer.access$100(Analyzer.java:24) at application.Analyzer$1.stateChanged(Analyzer.java:101) at javax.swing.JTabbedPane.fireStateChanged(JTabbedPane.java:416) at javax.swing.JTabbedPane$ModelListener.stateChanged(JTabbedPane.java:270) at javax.swing.DefaultSingleSelectionModel.fireStateChanged(DefaultSingleSelectionModel.java:132) at javax.swing.DefaultSingleSelectionModel.setSelectedIndex(DefaultSingleSelectionModel.java:67) at javax.swing.JTabbedPane.setSelectedIndexImpl(JTabbedPane.java:616) at javax.swing.JTabbedPane.insertTab(JTabbedPane.java:735) at application.Analyzer.addTab(Analyzer.java:133)

So when you insert a tab, it automatically triggers a change of selected tab which in turns calls your ChangeEventListener which will trigger the insertion of a tab etc...

So you have two simple solutions:

1. Use a flag (a boolean ) that is set to true before you add the new tab and that you set back to false when you are done. In your condition to test if you need to add a tab, you also check that this flag is not true .
2. You remove your change listener from the JTabbedPane before you insert the tab and you put it back afterwards.

In both case, use a try/finally block to make sure to return to a consistent state.

Answer 2

UPDATED SOLUTION Sorry, the previous solution is not working as expected. Here my updated one:

public class TabbedPaneTest {

    private final static JButton ADD_NEW_TAB_BUTTON = new JButton();
    private JFrame mainFrame;
    private JTabbedPane tabbedPane;

    public void run() {
        mainFrame = new JFrame("Test JTabbedPane");
        mainFrame.setSize(300, 400);
        mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        tabbedPane = new JTabbedPane();
        tabbedPane.addTab("default new tab", new JLabel("this is a default tab"));

        addNewTabButton();
        tabbedPane.addChangeListener(new ChangeListener() {

            @Override
            public void stateChanged(ChangeEvent e) {
                if (tabbedPane.getSelectedComponent() == ADD_NEW_TAB_BUTTON) {
                    tabbedPane.addTab("new tab", new JLabel("new tab label"));
                    addNewTabButton();
                }
            }
        });


        mainFrame.getContentPane().add(tabbedPane);
        mainFrame.setVisible(true);
    }

    private void addNewTabButton() {
        tabbedPane.remove(ADD_NEW_TAB_BUTTON);
        tabbedPane.addTab("[+]", ADD_NEW_TAB_BUTTON);
    }

    public static void main(String[] params) {
        TabbedPaneTest test = new TabbedPaneTest();
        test.run();
    }

}

Answer 3

The problem is that the changeListener is called after the adding once again with the + tab as the selected tab, causing the creation of a new tab, and so on.

a pretty simple solution could be just to add a bool flag as Guillaume Polet stated :

    songPanel.addChangeListener(new ChangeListener(){

        @Override //Method called when selected tab changes
        public void stateChanged(ChangeEvent e){
            try {   
                if(songPanel.getSelectedIndex()==songPanel.getTabCount()-1 && !adding){
                    adding = true;
                    addTab("songPanel");
                    adding = false;
                }
            } catch (StackOverflowError soe){soe.printStackTrace();}
        }
    });

The adding flag is a class field initialized to false, and indicates whether or not you are in progress of adding a tab. Minor changes to the addTab to get everything to work:

private void addTab(String panelName){
    System.out.println("ADDING TAB");
    if(panelName.equals("songPanel")){
        String tabName = ("#" + Integer.toString(songPanel.getTabCount()));
        int index = songPanel.getTabCount()-1;
        songPanel.insertTab(tabName, null, new JTextField(), tabName, index);
        songPanel.setSelectedIndex(index);
    }
}

I made a little change in code, making the active tab the newly created one, and the indexes where a bit off.

Hope this helps :)