我有一个家庭作业，我正在构建一个 GUI JPane，它包含其他 JPanes 以允许显示多个对象。我的一位听众出现编译错误，可以使用一些帮助来解决这个问题。让我先说我们不允许使用 IDE。
错误是：
F:\Java\Lab 8\Lab8.java:84: error: cannot find symbol
jcbo.addListSelectionListener(new ListSelectionListener() {
^
symbol: method addListSelectionListener(<anonymous ListSelectionListener>)
location: variable jcbo of type JComboBox<String>
1 error
项目代码为：
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.util.Scanner;
import java.util.EventObject;
public class Lab8 extends JFrame {
public String name;
public String[] ageRanges = {"Select an Age Range","Under 20", "20-29", "30-39", "40-49", "50-59", "60 and Above"};
public String[] destination = {"Mercury", "Venus", "Moon", "Mars", "Jupiter / Europa", "Saturn / Triton", "Pluto + Sharon"};
final JTextField txtName = new JTextField(20);
String value;
public Lab8()
{
// Create an array of Strings for age ranges
final JComboBox<String> jcbo = new JComboBox<String>(ageRanges);
jcbo.setForeground(Color.blue);
jcbo.setBackground(Color.white);
// Create an array of String destinations
// Declare radio buttons
JRadioButton jrbMonday, jrbTuesday, jrbWednesday, jrbThursday, jrbFriday;
// Create a textfield
JTextField jMsg = new JTextField(10);
// Create panel to hold label and textbox.
JPanel p1 = new JPanel();
p1.setLayout(new BorderLayout(5,0));
p1.add(new JLabel("Name: "), BorderLayout.WEST);
p1.add(txtName, BorderLayout.CENTER);
jMsg.setHorizontalAlignment(JTextField.LEFT);
// Create combobox panel.
JPanel p2 = new JPanel();
p2.setLayout(new GridLayout(2,0,5,5));
p2.add(p1, BorderLayout.NORTH);
p2.add(new JComboBox<String>(ageRanges), BorderLayout.CENTER);
p2.setBorder(new TitledBorder("Passenger Name & Age Range"));
final JList<String> jlst = new JList<String>(destination);
//Create listbox panel.
JPanel p3 = new JPanel();
p3.setLayout(new GridLayout(1, 0));
p3.add(jlst);
p3.setBorder(new TitledBorder("Destinations"));
jlst.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e){
final int index = jlst.getSelectedIndex();
value = destination[index];
}
});
jcbo.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e){
final int index = jcbo.getSelectedIndex();
value = ageRanges[index];
}
});
// Create a print button
JButton jbtPrint = new JButton("Print");
// Create a new panel to hold radio buttons.
JPanel r1 = new JPanel();
r1.setLayout(new GridLayout(3,2));
r1.add(jrbMonday = new JRadioButton("Monday"));
r1.add(jrbTuesday = new JRadioButton("Tuesday"));
r1.add(jrbWednesday = new JRadioButton("Wednesday"));
r1.add(jrbThursday = new JRadioButton("Thursday"));
r1.add(jrbFriday = new JRadioButton("Friday"));
r1.setBorder(new TitledBorder("Departure Days"));
r1.add(jbtPrint);
// Create a radio button group to group five buttons
ButtonGroup group = new ButtonGroup();
group.add(jrbMonday);
group.add(jrbTuesday);
group.add(jrbWednesday);
group.add(jrbThursday);
group.add(jrbFriday);
// Create grid to hold contents
JPanel pMain = new JPanel();
pMain.setLayout(new BorderLayout(5,0));
add(r1, BorderLayout.CENTER);
add(p2, BorderLayout.NORTH);
add(p3, BorderLayout. EAST);
// Create button listener
jbtPrint.addActionListener(new ButtonListener());
jrbMonday.addActionListener(new mListener());
jrbTuesday.addActionListener(new tListener());
jrbWednesday.addActionListener(new wListener());
jrbThursday.addActionListener(new rListener());
jrbFriday.addActionListener(new fListener());
}
int flag = 0;
// Declare radio button variable
boolean monday, tuesday, wednesday, thursday, friday;
public void monday(){
monday = true;
}
public void tuesday(){
tuesday = true;
}
public void wednesday(){
wednesday = true;
}
public void thursday(){
thursday = true;
}
public void friday(){
friday = true;
}
public class mListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
monday();
flag = 1;
}
}
public class tListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
tuesday();
flag = 2;
}
}
public class wListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
wednesday();
flag = 3;
}
}
public class rListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
thursday();
flag = 4;
}
}
public class fListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
friday();
flag = 5;
}
}
public void setText(){
name = txtName.getText();
}
/** Handle the print button */
class ButtonListener implements ActionListener {
ButtonListener(){
}
public void actionPerformed(ActionEvent e) {
// Get values from fields
setText();
System.out.println("Passenger's Name: " + name + "\n");
System.out.println("Age Group: " + ageRanges + "\n");
System.out.println("Destination: " + value + "\n");
System.out.println("Departure Day: " + flag + "\n");
}
/*jbtPrint.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
}
});*/
}
public static void main(String[] args)
{
Lab8 frame = new Lab8();
// frame.pack();
frame.setTitle("Lab 8 Application");
frame.setLocationRelativeTo(null); // Center the frame
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(425, 275);
frame.setVisible(true);
}
}