使用sql从comobBox项目自动填充Jfields

Question

我正在尝试实现一个代码，该代码允许用户从comboBox中选择视频的名称，然后让sql从数据库中返回与txtfields相对应的值。 我的组合框的sql语句返回值，直到我添加了ActionEvent，但现在没有任何值。

package project_files;

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JComboBox;
import javax.swing.JTextField;

public class videointerface_registered {

    private JFrame frame;
    private JTextField txtSubject;
    private JTextField txtDescription;
    private JTextField txtCity;
    private JTextField txtTags;
    private JTextField txtUser;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    videointerface_registered window = new videointerface_registered();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public videointerface_registered() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        JLabel lblVideoName = new JLabel("Video Name");
        lblVideoName.setBounds(33, 27, 103, 14);
        frame.getContentPane().add(lblVideoName);

        final JComboBox<String> comboBox = new JComboBox<String>();
        comboBox.setBounds(205, 24, 203, 20);
        frame.getContentPane().add(comboBox);
            comboBox.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent argo0) {

          try {
              Class.forName("com.mysql.cj.jdbc.Driver");
                Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/userdatabase", "root", "pass1234");

                    String SQL1="Select video_name from video";
                    PreparedStatement ps=con.prepareStatement(SQL1);
                        ResultSet rs = ps.executeQuery();
                        while(rs.next()) {
                            comboBox.addItem(rs.getString("video_name"));
             txtDescription.setText("video_description");
             txtSubject.setText("video_subject");
             txtCity.setText("video_city");
             txtUser.setText("userid");
             txtTags.setText("video_tags");
        }


            rs.close();
            ps.close();
        } catch (Exception e3) {
            e3.printStackTrace();
            System.exit(0);
        }
    }
});


        JLabel lblDescription = new JLabel("Video Description");
        lblDescription.setBounds(38, 64, 46, 14);
        frame.getContentPane().add(lblDescription);

        JLabel lblVideoSubject = new JLabel("Video Subject");
        lblVideoSubject.setBounds(33, 108, 46, 14);
        frame.getContentPane().add(lblVideoSubject);

        JLabel lblCity = new JLabel("City");
        lblCity.setBounds(33, 159, 46, 14);
        frame.getContentPane().add(lblCity);

        JLabel lblUser = new JLabel("Posted by");
        lblUser.setBounds(33, 221, 46, 14);
        frame.getContentPane().add(lblUser);

        JLabel lblTags = new JLabel("Tags");
        lblTags.setBounds(33, 196, 46, 14);
        frame.getContentPane().add(lblTags);

        txtSubject = new JTextField();
        txtSubject.setEditable(false);
        txtSubject.setBounds(204, 61, 86, 20);
        frame.getContentPane().add(txtSubject);
        txtSubject.setColumns(10);

        txtDescription = new JTextField();
        txtDescription.setEditable(false);
        txtDescription.setBounds(204, 105, 86, 20);
        frame.getContentPane().add(txtDescription);
        txtDescription.setColumns(10);

        txtCity = new JTextField();
        txtCity.setEditable(false);
        txtCity.setBounds(205, 156, 86, 20);
        frame.getContentPane().add(txtCity);
        txtCity.setColumns(10);

        txtTags = new JTextField();
        txtTags.setEditable(false);
        txtTags.setBounds(205, 193, 86, 20);
        frame.getContentPane().add(txtTags);
        txtTags.setColumns(10);

        txtUser = new JTextField();
        txtUser.setEditable(false);
        txtUser.setBounds(204, 221, 86, 20);
        frame.getContentPane().add(txtUser);
        txtUser.setColumns(10);





        }   
    }