Java：如何从JcomboBox获取字符串

我看过类似的问题，但例子和答案都太复杂了，我无法理解

我正在处理这个项目，基本上需要能够从combobox菜单中选择项，以便在JDBC中运行查询。我得到了JDBC部分的帮助

问题：我对使用ActionListener、ItemStateChanged或两者都使用感到困惑

还有，我需要在上面的方法中加入哪部分代码

谢谢你的帮助`

    package userProfile;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

public class Database extends GUI implements ActionListener   {

        JFrame frame;
        JButton search;
        JComboBox fromLoc, toLoc, fromDate, fromTime;
        JLabel fromLabel, toLabel, fromDateLabel, fromTimeLabel;
        PreparedStatement ps = null;
        Connection link;
        ResultSet rs = null;

    public  Database() {

        frame = new JFrame("Make a Reservation");
        frame.getContentPane().setLayout(null);     

        //Arrival date/time comboBoxes and labels
        fromDateLabel = new JLabel("Departure Date");
        fromDateLabel.setBounds(50,230,100,30);
        fromDate = new JComboBox(new String[]{"12/15/2015", 
                  "12/21/2015", "12/21/2015", "12/24/2015"});
        fromDate.addActionListener(this);
        fromDate.setBounds(50,200,100,30);

        fromTimeLabel = new JLabel("Departure Time");
        fromTimeLabel.setBounds(160,230,100,30);
        fromTime = new JComboBox(new String[]{"13:00", 
                  "15:00", "15:30", "08:00"});
        fromTime.addActionListener(this);
        fromTime.setBounds(160,200,100,30);

        //Departure label and comboBox
        fromLabel = new JLabel("Departure");
        fromLabel.setBounds(50,300,100,30);
        fromLoc = new JComboBox(new String[]{"Atlanta", 
                  "Charleston", "New York", "Los Angeles", 

"Orlando", "San Francisco"});
        fromLoc.addActionListener(this);
        fromLoc.setBounds(50,270,100,30);

        toLabel = new JLabel("Arrival");
        toLabel.setBounds(160,300,100,30);
        toLoc = new JComboBox(new String[]{"Atlanta", 
                  "Charleston", "New York", "Los Angeles", "Orlando", "San Francisco"});
        toLoc.addActionListener(this);
        toLoc.setBounds(160,270,100,30);

        search = new JButton("Ok");
        search.addActionListener(this);
        search.setBounds(270,270,100,30);
        //adding the buttons in frame
        frame.getContentPane().add(fromDateLabel);
        frame.getContentPane().add(fromDate);
        frame.getContentPane().add(fromTimeLabel);
        frame.getContentPane().add(fromTime);
        frame.getContentPane().add(fromLabel);
        frame.getContentPane().add(fromLoc);
        frame.getContentPane().add(toLabel);
        frame.getContentPane().add(toLoc);
        frame.getContentPane().add(search);

        frame.setSize(400,400);
        frame.setVisible(true);


        StateChange state = new StateChange();

          try {
                // Driver for mysql
                Class.forName("com.mysql.jdbc.Driver");
                 // connection link obj
                 link = DriverManager.getConnection("jdbc:mysql://localhost:3306/world", "root", "root");   
                 // query statement obj
                 ps = link.prepareStatement("select * from flights where from_date = ? and from_loc = ? and to_loc = ?");

                 ps.setString(1, fromD);
                 ps.setString(2, fromL);
                 ps.setString(3, toL);

                 rs = ps.executeQuery();

                 while (rs.next()) {


                }

                } catch (SQLException sqle) {
                    System.out.println("An error occurred.Maybe user/password is invalid");
                    sqle.printStackTrace();
                } catch (ClassNotFoundException cfne) {
                    cfne.printStackTrace();
                }

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub

    }

        private class StateChange implements ItemListener {

    @Override
    public void itemStateChanged(ItemEvent e) {
        // TODO Auto-generated method stub
        // if (e.getStateChange() == ItemEvent.SELECTED) {
          //  String toLoc = (String)e.getItem();
           // System.out.println(s);

        // here i just used strings to get content from comboBox
                String fromL = fromLoc.getSelectedItem().toString();
                String fromD = fromDate.getSelectedItem().toString();
                String toL = toLoc.getSelectedItem().toString();

    }
        }
}

---

您只需要重写actionPerformed（）方法，下面是获取所选选项文本的方法

public void actionPerformed(ActionEvent e) {
    JComboBox fromL = (JComboBox)e.getSource();
    String fromL = (String) fromLoc.getSelectedItem();

    // do whatever you want with the values
    ...
  }

现在您已经从相应的组合框中选择了文本，现在您可以使用这些文本了。请参阅链接中的“在组合框上处理事件”部分 如果你还有任何疑问