使用JScrollPane

Question

我有一份就业历史GUI。如果用户想要添加更多历史记录，他们会单击添加按钮并在当前窗格下方，它将添加另一个用户表单，用户可以在其中输入更多信息。我不知道该怎么做。此外，我有一个返回上一帧的按钮，但我希​​望用户能够看到他们在前一帧中输入的内容，而不是创建一个新的帧。任何帮助将不胜感激。到目前为止，这是我的代码：

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;
import javax.swing.border.EmptyBorder;

public class EmploymentHistory extends JFrame {

    private JButton btnClear, btnNext, btnPrevious, btnAddMoreEmployment;
    private JLabel labelEmployer, labelPosition, labelStart, labelEnd, labelDuties,
            labelReason, labelPhoneNum;
    private JTextField txtEmployer, txtPosition, txtStart, txtEnd, txtPhoneNum;
    private JTextArea areaDuties, areaReason;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new EmploymentHistory().setVisible(true);
            }
        });
    }

    public EmploymentHistory() {
        createView();

        setTitle("Employment History");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(600, 500);
        setMinimumSize(new Dimension(600, 500));
        setLocationRelativeTo(null);
        setResizable(false);
    }

    private void createView() {
        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        getContentPane().add(panel);

        // add scroll pane to move down
        northPanel(panel);

        centerPanel(panel);

        southPanel(panel);
    }

    private void northPanel(JPanel panel) {
        JPanel northPanel = new JPanel();
        northPanel.setBackground(Color.GRAY);
        panel.add(northPanel, BorderLayout.NORTH);

        JLabel labelEmployment = new JLabel("Employment Information");
        labelEmployment.setFont(new Font("Serif", Font.BOLD, 25));
        northPanel.add(labelEmployment, BorderLayout.CENTER);
    }

    private void centerPanel(JPanel panel) {
        JPanel centerPanel = new JPanel();
        centerPanel.setBackground(Color.yellow);
        centerPanel.setSize(300, 300);
        GridBagLayout layout = new GridBagLayout();

        centerPanel.setLayout(layout);
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.anchor = GridBagConstraints.LINE_END;

        labelEmployer = new JLabel("Employer: ");
        labelEmployer.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelEmployer, gbc);
        gbc.gridy++;

        labelPosition = new JLabel("Position: ");
        labelPosition.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelPosition, gbc);
        gbc.gridy++;

        labelPhoneNum = new JLabel("Employer's Phone Number: ");
        labelPhoneNum.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelPhoneNum, gbc);
        gbc.gridy++;

        labelStart = new JLabel("Start Date: ");
        labelStart.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelStart, gbc);
        gbc.gridy++;

        labelEnd = new JLabel("End Date: ");
        labelEnd.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelEnd, gbc);
        gbc.gridy++;

        labelDuties = new JLabel("Duties: ");
        labelDuties.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelDuties, gbc);
        gbc.gridy++;

        labelReason = new JLabel("Reason for leaving: ");
        labelReason.setFont(new Font("Serif", Font.PLAIN, 15));
        centerPanel.add(labelReason, gbc);
        gbc.gridy++;

        //reseting
        gbc.gridx = 1;
        gbc.gridy = 0;
        gbc.anchor = GridBagConstraints.LINE_START;

        txtEmployer = new JTextField(25);
        txtEmployer.setHorizontalAlignment(JTextField.CENTER);
        txtEmployer.setHorizontalAlignment(SwingConstants.LEFT);
        centerPanel.add(txtEmployer, gbc);
        gbc.gridy++;

        txtPosition = new JTextField(25);
        txtPosition.setHorizontalAlignment(JTextField.CENTER);
        txtPosition.setHorizontalAlignment(SwingConstants.LEFT);
        centerPanel.add(txtPosition, gbc);
        gbc.gridy++;

        txtPhoneNum = new JTextField(25);
        txtPhoneNum.setHorizontalAlignment(JTextField.CENTER);
        txtPhoneNum.setHorizontalAlignment(SwingConstants.LEFT);
        centerPanel.add(txtPhoneNum, gbc);
        gbc.gridy++;

        txtStart = new JTextField(25);
        txtStart.setHorizontalAlignment(JTextField.CENTER);
        txtStart.setHorizontalAlignment(SwingConstants.LEFT);
        centerPanel.add(txtStart, gbc);
        gbc.gridy++;

        txtEnd = new JTextField(25);
        txtEnd.setHorizontalAlignment(JTextField.CENTER);
        txtEnd.setHorizontalAlignment(SwingConstants.LEFT);
        centerPanel.add(txtEnd, gbc);
        gbc.gridy++;

        areaDuties = new JTextArea();
        areaDuties.setLineWrap(true);
        areaDuties.setWrapStyleWord(true);
        JScrollPane scrollPane = new JScrollPane(areaDuties);
        scrollPane.setPreferredSize(new Dimension(315, 90));
        centerPanel.add(scrollPane, gbc);
        gbc.gridy++;

        areaReason = new JTextArea();
        areaReason.setLineWrap(true);
        areaReason.setWrapStyleWord(true);
        JScrollPane scrollPaneReason = new JScrollPane(areaReason);
        scrollPaneReason.setPreferredSize(new Dimension(315, 90));
        centerPanel.add(scrollPaneReason, gbc);
        gbc.gridy++;

        btnAddMoreEmployment = new JButton("Add More");
        btnAddMoreEmployment.addActionListener(new ButtonAddMoreActionListener());
        centerPanel.add(btnAddMoreEmployment, gbc);
        gbc.gridy++;

        panel.add(centerPanel);
    }

    private void southPanel(JPanel panel) {
        JPanel southPanel = new JPanel();
        southPanel.setBackground(Color.GREEN);
        panel.add(southPanel, BorderLayout.SOUTH);

        btnPrevious = new JButton("PREVIOUS");
        btnPrevious.addActionListener(new ButtonPreviousActionLisener());
        southPanel.add(btnPrevious);

        btnClear = new JButton("CLEAR");
        southPanel.add(btnClear);

        btnNext = new JButton("NEXT");
        southPanel.add(btnNext);
    }

    private class ButtonAddMoreActionListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            JPanel panel = new JPanel();
            panel.setLayout(new BorderLayout());
            getContentPane().add(panel);

            JScrollPane scrollPane = new JScrollPane(panel);
            scrollPane.setPreferredSize(new Dimension(315, 90));
            panel.add(scrollPane);

            centerPanel(panel);

        }
    }

    private class ButtonPreviousActionLisener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            BasicInfo goBasic = new BasicInfo();
            goBasic.setVisible(true);
        }
    }
}