Java BoxLayout returning error BoxLayout can't be shared

StackOverflow https://stackoverflow.com/questions/21428080

  •  04-10-2022
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Question

The following code for laying out components returns error

public class MainPanel extends JPanel
{
    private JTextField txt1, txt2;
    private JButton btnCopy, btnCut, btnDel;
    private JPanel wrapper1, wrapper2;

    public MainPanel()
    {
        txt1 = new JTextField();
        txt2 = new JTextField();

        btnCopy = new JButton("Copy");
        btnCut = new JButton("Cut");
        btnDel = new JButton("Delete");

        wrapper1 = new JPanel();
        wrapper1.setLayout(new BoxLayout(wrapper1, BoxLayout.Y_AXIS));
        wrapper1.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        wrapper1.add(txt1);
        wrapper1.add(txt2);

        wrapper2 = new JPanel();
        wrapper2.setLayout(new BoxLayout(wrapper1, BoxLayout.Y_AXIS));
        wrapper2.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        wrapper2.add(btnCopy);
        wrapper2.add(btnCut);
        wrapper2.add(btnDel);

        setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
        add(wrapper1);
        add(wrapper2);
    }
}

I am aware of similar question BoxLayout can't be shared error but it doesn't address my problem, as I am not using JFrame but JPanel instead

Error:

Exception in thread "AWT-EventQueue-0" java.awt.AWTError: BoxLayout can't be shared
at javax.swing.BoxLayout.checkContainer(BoxLayout.java:464)
at javax.swing.BoxLayout.invalidateLayout(BoxLayout.java:248)
at javax.swing.BoxLayout.addLayoutComponent(BoxLayout.java:281)
at java.awt.Container.addImpl(Container.java:1120)
at java.awt.Container.add(Container.java:410)
at copycut.MainPanel.<init>(MainPanel.java:39)
at copycut.CopyCut.<init>(CopyCut.java:23)
at copycut.CopyCut$1.run(CopyCut.java:39)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:727)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:688)
at java.awt.EventQueue$3.run(EventQueue.java:686)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:697)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
Was it helpful?

Solution

I believe that instead of:

wrapper2.setLayout(new BoxLayout(wrapper1, BoxLayout.Y_AXIS));

You want to do:

wrapper2.setLayout(new BoxLayout(wrapper2, BoxLayout.Y_AXIS));

For now, you create a new BoxLayout with wrapper1 for parent and try to "share" it by making it the layout of wrapper2. It's just a mistyping (or most probably some omission after a quick copy/paste) :p

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