Question

I can seek the items randomly in Jlist with a next button. When I press the next button fastly, I’m getting the exception: Exception in thread “Thread-7” java.lang.ClassCastException: sun.java2d.NullSurfaceData cannot be cast to sun.java2d.d3d.D3DSurfaceData
So since the frequency of clicking next triggers this problem can we say there’s something wrong with threads? As a note there is no update in jlist. Jlist is been initialized and filled with elements at start and then just seeking the items randomly with the next button.
If I remove ensureIndexIsVisible then there’s no trouble.

I hope below summary code helps:

public class B_Object {
    private NewJFrame njf = new NewJFrame();
    HandlePlay hPlay = new HandlePlay(njf);

    njf.nextButton.addActionListener(new java.awt.event.ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            playNext();                
        }
    });
}

public class HandlePlay {
    private NewJFrame n_j_f;
    HandlePlay(NewJFrame njf){
        n_j_f = njf;
    }
    private void setDisplay(int i) {
        String str = "dummy";
        n_j_f.jList1.setSelectedIndex(i);
        n_j_f.setTitle(str);
        n_j_f.jTextArea1.setText(str);
        n_j_f.jList1.ensureIndexIsVisible(n_j_f.jList1.getSelectedIndex());
    }
}

Answer 1

After trying different threads and searching the event dispatch thread I found it’s related with EDT. To solve this issue following modification is enough:

private void test(final int i) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            jList1.setSelectedIndex(i);
            System.out.println("javax.swing.SwingUtilities.isEventDispatchThread()=" + javax.swing.SwingUtilities.isEventDispatchThread());
            jList1.ensureIndexIsVisible(i);
        }
    });
}

So make sure that if you have such gui problems intermittenly occuring, check if you’re doing that operation within the EDT, checking by isEventDispatchThread().