JComboBox实现键值绑定

例子1(没有对数据库操作)：

import java.awt.BorderLayout;

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Vector;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class ComboBoxItem extends JFrame implements ActionListener {
  public ComboBoxItem() {
    Vector model = new Vector();
    model.addElement(new Item(1, "car"));
    model.addElement(new Item(2, "plane"));
    model.addElement(new Item(3, "train"));
    model.addElement(new Item(4, "boat"));
    JComboBox comboBox;

    // Easiest approach is to just override toString() method
    // of the Item class

    comboBox = new JComboBox(model);
    // comboBox.setDragEnabled(true);
    comboBox.addActionListener(this);
    getContentPane().add(comboBox, BorderLayout.NORTH);

    // Most flexible approach is to create a custom render
    // to diplay the Item data

    comboBox = new JComboBox(model);
    // comboBox.setDragEnabled(true);
    comboBox.setRenderer(new ItemRenderer());
    comboBox.addActionListener(this);
    getContentPane().add(comboBox, BorderLayout.SOUTH);
  }

  public void actionPerformed(ActionEvent e) {
    JComboBox comboBox = (JComboBox) e.getSource();
    Item item = (Item) comboBox.getSelectedItem();
    System.out.println(item.getId() + " : " + item.getDescription());
  }

  class ItemRenderer extends BasicComboBoxRenderer {
    public Component getListCellRendererComponent(JList list, Object value, int index,
        boolean isSelected, boolean cellHasFocus) {
      super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);

      if (value != null) {
        Item item = (Item) value;
        setText(item.getDescription().toUpperCase());
      }

      if (index == -1) {
        Item item = (Item) value;
        setText("" + item.getId());
      }

      return this;
    }
  }

  class Item {
    private int id;
    private String description;

    public Item(int id, String description) {
      this.id = id;
      this.description = description;
    }

    public int getId() {
      return id;
    }

    public String getDescription() {
      return description;
    }

    public String toString() {
      return description;
    }
  }

  public static void main(String[] args) {
    JFrame frame = new ComboBoxItem();
    frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
  }

}

例子2（对数据库操作）：

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.plaf.basic.BasicComboBoxRenderer;

public class ComboKeyValue extends JFrame implements ActionListener {
  public ComboKeyValue() {

    JComboBox comboBox;
    Vector model = new Vector();
    String locationid = "";
    String locationname = "";
    try {
      Connection conn = getConnection();
      Statement st = conn.createStatement();
      String sqllocations = "select id, name from locations";
      ResultSet rss = st.executeQuery(sqllocations);
      while (rss.next()) {
        locationid = rss.getString("id");
        locationname = rss.getString("name");
        KeyValue Itemlocation = new KeyValue(locationid, locationname);
        model.addElement(Itemlocation);
      }

    } catch (SQLException e) {
      e.printStackTrace();
    }

    comboBox = new JComboBox(model);
    comboBox.addActionListener(this);
    getContentPane().add(comboBox, BorderLayout.NORTH);

  }

  public void actionPerformed(ActionEvent e) {
    JComboBox comboBox = (JComboBox) e.getSource();
    KeyValue item = (KeyValue) comboBox.getSelectedItem();
    System.out.println(item.getId() + " 对应 " + item.getName());
  }

 
  class KeyValue {
    private String id;
    private String name;

    public KeyValue(String id, String name) {
      this.id = id;
      this.name = name;
    }

    public String getId() {
      return id;
    }

    public String getName() {
      return name;
    }

    public String toString() {
      return name;
    }
  }

  public static Connection getConnection() {
    Connection conn = null;
    Statement stmt = null;

    try {
      Class.forName("org.postgresql.Driver");
    } catch (ClassNotFoundException ce) {
      System.out.print(ce.getMessage());
    }
    try {
      String url = "jdbc:postgresql://localhost:5432/openbravopos";
      String username = "postgres";
      String password = "123";
      conn = DriverManager.getConnection(url, username, password);
      stmt = conn.createStatement();
    } catch (Exception e) {
      System.out.println(e.getMessage());
    }
    return conn;
  }

  public static void main(String[] args) {
    JFrame frame = new ComboKeyValue();
    frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
  }

}