清华大学：JAVA教学课件：8-5

程序8-5
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class JComboBoxDemo {
JFrame frame = new JFrame ("JComboBox Demo");
JComboBox jcb1,jcb2;
JTextArea ta = new JTextArea(0,30); //用于显示结果的文本区
public static void main(String args[]){
JComboBoxDemo cbd = new JComboBoxDemo();
cbd.go();
}
public void go() {
//创建内部JPanel容器
JPanel p1 = new JPanel();
JPanel p2 = new JPanel();
JPanel p3 = new JPanel();
JPanel p4 = new JPanel();
String[] itemList = { "One","Two","Three","Four","Five" };
jcb1 = new JComboBox(itemList);
jcb1.setSelectedIndex(3); //设置第4个可选项为当前的显示项
p1.add(jcb1);
Border etched = BorderFactory.createEtchedBorder();
Border border = BorderFactory.createTitledBorder(etched,"Uneditable JComboBox");
p1.setBorder(border);
jcb2 = new JComboBox();
//添加4个可选项
jcb2.addItem("Six");
jcb2.addItem("Seven");
jcb2.addItem("Eight");
jcb2.addItem("nine");
//将jcb2设置为可编辑的
jcb2.setEditable(true);

p2.add(jcb2);
border = BorderFactory.createTitledBorder(etched,"Editable JComboBox");
p2.setBorder(border);

JScrollPane jp = new JScrollPane(ta);
p3.setLayout(new BorderLayout());
p3.add(jp);
border = BorderFactory.createTitledBorder(etched,"Results");
p3.setBorder(border);
ActionListener al = new ActionListener() {
public void actionPerformed(ActionEvent e) {
JComboBox jcb = (JComboBox)e.getSource();
if (jcb == jcb1) {
//将选项插入jcb2的第一个位置
jcb2.insertItemAt(jcb1.getSelectedItem(),0);
ta.append("\nItem "+ jcb1.getSelectedItem() +" inserted");
} else {
ta.append("\n You selected item,"+ jcb2.getSelectedItem());
jcb2.addItem(jcb2.getSelectedItem());
}
}
};
jcb1.addActionListener(al);
jcb2.addActionListener(al);
p4.setLayout(new GridLayout(0,1));
p4.add(p1);
p4.add(p2);
Container cp = frame.getContentPane();
cp.setLayout(new GridLayout(0,1));
cp.add(p4);
cp.add(p3);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
}