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); } }
