Java：如何從JcomboBox獲得字符串

Question

我已經看過類似的問題，但這兩個例子和答案太複雜，我不明白。

我正在處理項目，基本上需要能夠從組合框選擇項目，所以我可以在JDBC中運行查詢。我在JDBC部分獲得了幫助。

問題：我很困惑天氣使用ActionListener，ItemStateChanged或兩者！

而且我還需要在上述方法中加入哪部分代碼。

感謝您help`

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(); 

    } 
     } 
} 

Answer 1

你只需要重寫actionPerformed（）方法，這裏是獲得所選選項的文本

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

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

現在，你有文本的方法現在您可以使用文本從相應的組合框中選擇。如果您仍有任何疑問，請參閱：在組合框中處理事件的鏈接https://docs.oracle.com/javase/tutorial/uiswing/components/combobox.html 。