What's wrong with JList in JScrollPanel

  I want to design a Frame which cotains 2 buttons. When I click
button1, the frame display a JPanel(Panel1) and when I click

 button2, it displays another JPanel(Panel2).

  codes in Frame1:
        jButton1.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e) {
                if (selected != null)
                    Frame1.this.remove(selected);
                selected = new Panel1();

                selected.setBounds(0, 0, 400, 300);
                Frame1.this.add(selected);
                Frame1.this.repaint();

            }
        });

There is a JLabel and a JScorllPane which contains a JList in Panel1
There is a JList and a JScorllPane which contains a JList in Panel1
In Panel1, JLabel can display correctly. But JScrollPanel display
nothing.
In Panel2, JList can display correctly. But JScrollPanel display
nothing.

What's wrong with JList in JScrollPane?

Panel1 and Panel2:

public class Panel1 extends JPanel {
    public Panel1() {
        try {
            jbInit();
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    private void jbInit() throws Exception {
        this.setLayout(null);
        DefaultListModel model=new DefaultListModel();
        model.addElement("1");
        model.addElement("2");
        jList1.setModel(model);
        jScrollPane1.setBounds(new Rectangle(59, 62, 285, 131));
        jLabel1.setText("jLabel1");
        jLabel1.setBounds(new Rectangle(62, 25, 151, 23));
        this.add(jScrollPane1);
        this.add(jLabel1);
        jScrollPane1.getViewport().add(jList1);
    }

    JScrollPane jScrollPane1 = new JScrollPane();
    JList jList1 = new JList();
    JLabel jLabel1 = new JLabel();
}

public class Panel2 extends JPanel {
    public Panel2() {
        try {
            jbInit();
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }

    private void jbInit() throws Exception {
        this.setLayout(null);
        DefaultListModel model=new DefaultListModel();
        model.addElement("1");
        model.addElement("2");
        jList1.setModel(model);
        jList2.setModel(model);
        jScrollPane1.setBounds(new Rectangle(86, 61, 236, 161));
        jList2.setBounds(new Rectangle(73, 11, 65, 29));
        this.add(jScrollPane1);
        this.add(jList2);
        jScrollPane1.getViewport().add(jList1);
    }

    JScrollPane jScrollPane1 = new JScrollPane();
    JList jList1 = new JList();
    JList jList2 = new JList();
}