问使用jbutton打开新窗口时遇到问题

EN

import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

import org.jpedal.PdfDecoder;
import org.jpedal.examples.viewer.Viewer;
import org.jpedal.gui.GUIFactory;
import org.jpedal.utils.LogWriter;

public class Button extends Viewer {

    private MyPanel panel1;
    private MyPanel2 panel2;

    private void displayGUI() {
        JFrame frame = new JFrame("eBookReader Button");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPane = new JPanel();
        contentPane.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new CardLayout());
        panel1 = new MyPanel(contentPane);
        contentPane.add(panel1, "Panel 1");
        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String args[]) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new Button().displayGUI();
            }
        });
    }
}

class MyPanel extends JPanel {

    private JButton jcomp4;
    private JPanel contentPane;

    public MyPanel(JPanel panel) {

        contentPane = panel;

        jcomp4 = new JButton("openNewWindow");

        // adjust size and set layout
        setPreferredSize(new Dimension(315, 85));
        setLayout(null);
        jcomp4.setLocation(0, 0);
        jcomp4.setSize(315, 25);

        jcomp4.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    UIManager.setLookAndFeel(UIManager
                            .getSystemLookAndFeelClassName());
                } catch (Exception e1) {
                    LogWriter.writeLog("Exception " + e1
                            + " setting look and feel");
                }
                MyPanel2 a = new MyPanel2();
                a.setupViewer();

            }
        });

        add(jcomp4);
    }
}

class MyPanel2 extends Viewer {
    public MyPanel2() {

        // tell user we are in multipanel display
        currentGUI.setDisplayMode(GUIFactory.MULTIPAGE);

        // enable error messages which are OFF by default
        PdfDecoder.showErrorMessages = true;

    }

    public MyPanel2(int modeOfOperation) {

        // tell user we are in multipanel display
        currentGUI.setDisplayMode(GUIFactory.MULTIPAGE);

        // enable error messages which are OFF by default
        PdfDecoder.showErrorMessages = true;

        commonValues.setModeOfOperation(modeOfOperation);

    }
}