Tabbed Pane - problem

Pisze applet przy użyciu Tabbed Pane
Mam taki kod który w posiada dwie zakładki na pierwszej na razie jest przycisk i po naciśnięciu przycisku ustawiany jest wydruk do bufora . Po przejsciu na drugą zakładkę nastąpi wyrysowanie na panelu funkcji , tylko nie działa mi to tak do konca , bo jak przejdę na następną zakładkę to nie następuje automatycznie wyrysowanie obrazu, tylko jak ponownie nacisnę na zakładkę to zostanie ona wyrysowana .
A i jak zmienię rozmiar okna to obszar wyrysowania znika .

Co jest nie tak
Oto kod :

public class NewJApplet extends javax.swing.JApplet {
Image buffor;
Graphics bufor;

/** Initializes the applet NewJApplet */
@Override
public void init() {
    try {
        java.awt.EventQueue.invokeAndWait(new Runnable() {
            public void run() {
                initComponents();
                
            }
        });
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}



/** This method is called from within the init() method to
 * initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is
 * always regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    jTabbedPane1 = new javax.swing.JTabbedPane();
    jPanel1 = new javax.swing.JPanel();
    jButton1 = new javax.swing.JButton();
    jPanel2 = new javax.swing.JPanel();

    jTabbedPane1.addFocusListener(new java.awt.event.FocusAdapter() {
        public void focusGained(java.awt.event.FocusEvent evt) {
            jTabbedPane1FocusGained(evt);
        }
    });

    jButton1.setText("jButton1");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addGap(34, 34, 34)
            .addComponent(jButton1)
            .addContainerGap(286, Short.MAX_VALUE))
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addGap(45, 45, 45)
            .addComponent(jButton1)
            .addContainerGap(207, Short.MAX_VALUE))
    );

    jTabbedPane1.addTab("tab1", jPanel1);

    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 395, Short.MAX_VALUE)
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 275, Short.MAX_VALUE)
    );

    jTabbedPane1.addTab("tab2", jPanel2);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addGap(27, 27, 27)
            .addComponent(jTabbedPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 400, Short.MAX_VALUE)
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addGap(31, 31, 31)
            .addComponent(jTabbedPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 300, Short.MAX_VALUE)
            .addContainerGap())
    );
}// </editor-fold>

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
buffor = createImage(400,300);

buffor.getGraphics();
bufor = buffor.getGraphics();
bufor.drawLine(0, 0, 40, 40);

}

private void jTabbedPane1FocusGained(java.awt.event.FocusEvent evt) {
Graphics ekran;
ekran= jPanel2.getGraphics();
ekran.drawImage(buffor, 0, 0, this);

}

// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JTabbedPane jTabbedPane1;
// End of variables declaration

public void run() {
    throw new UnsupportedOperationException("Not supported yet.");
}

}