我有一个Java类的项目，需要我添加到JComboBoxes并设置事件，以便在点击它们时根据需要更改比萨饼价格。另外我知道事件代码有些不正确。它需要处理两个组合框，而且有些不正确。我很难理解我需要改变什么。这是代码：
// File name JPizza.java
// Written by Me
// Written on 4-26-2014
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JPizza extends JFrame implements ActionListener
{
final int EXTRALARGE_PRICE = 14;
final int LARGE_PRICE = 11;
final int MEDIUM_PRICE = 9;
final int SMALL_PRICE = 7;
final int CHEESE_PRICE = 0;
final int PEPPERONI_PRICE = 1;
final int SAUSAGE_PRICE = 1;
final int REDONION_PRICE = 1;
final int GREENPEPPER_PRICE = 1;
final int MUSHROOM_PRICE = 1;
int totalPrice = EXTRALARGE_PRICE + CHEESE_PRICE;
JLabel applicationLabel = new JLabel("Pizza Price Calculator");
JLabel optionExplainLabel = new JLabel("Select what size, and what topping you want from the drop down menus. Prices are listed in the combo boxes.");
JLabel pizzaSize = new JLabel("Pizza size");
JComboBox pizzaSizeValue = new JComboBox();
pizzaSizeValue.addItem("Extra Large - $14");
pizzaSizeValue.addItem("Large - $11");
pizzaSizeValue.addItem("Medium - $9");
pizzaSizeValue.addItem("Small - $7");
pizzaSizeValue.setSelectedItem("Extra Large - $14");
JLabel pizzaTopping = new JLabel ("Pizza topping");
JComboBox pizzaToppingValue = new JComboBox();
pizzaToppingValue.addItem("Cheese - free");
pizzaToppingValue.addItem("Pepperoni - $1");
pizzaToppingValue.addItem("Sausage - $1");
pizzaToppingValue.addItem("Red Onion - $1");
pizzaToppingValue.addItem("Green Pepper - $1");
pizzaToppingValue.addItem("Mushroom - $1");
pizzaToppingValue.setSelectedItem("Cheese - free");
JLabel priceLabel = new JLabel("The price for your pizza is");
JTextField totPrice = new JTextField(3);
public JPizza()
{
super("Pizza Price Calculator");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new FlowLayout());
add(applicationLabel);
add(optionExplainLabel);
add(pizzaSize);
add(pizzaSizeValue);
add(pizzaTopping);
add(pizzaToppingValue);
add(priceLabel);
add(totPrice);
totPrice.setText("$" + totalPrice);
pizzaSizeValue.addActionListener(this);
pizzaToppingValue.addActionListener(this);
}
public void actionPerformed(ActionEvent event)
{
int pizzaSizeCost = 14;
int pizzaToppingCost = 0;
JComboBox comboBox = (JComboBox) event.getSource();
Object source = event.getSource();
Object select = comboBox.getSelectedItem();
if(source == pizzaSizeValue)
{
if(select.equals("Extra Large - $14"))
pizzaSizeCost = EXTRALARGE_PRICE;
if(select.equals("Large - $11"))
pizzaSizeCost = LARGE_PRICE;
if(select.equals("Medium - $9"))
pizzaSizeCost = MEDIUM_PRICE;
if(select.equals("Small - $7"))
pizzaSizeCost = SMALL_PRICE;
}
if(source == pizzaToppingValue)
{
if(select.equals("Cheese - free"))
pizzaSizeCost = CHEESE_PRICE;
if(select.equals("Pepperoni $1"))
pizzaSizeCost = PEPPERONI_PRICE;
if(select.equals("Sausage $1"))
pizzaSizeCost = SAUSAGE_PRICE;
if(select.equals("Red Onion $1"))
pizzaSizeCost = REDONION_PRICE;
if(select.equals("Green Pepper $1"))
pizzaSizeCost = GREENPEPPER_PRICE;
if(select.equals("Mushroom $1"))
pizzaSizeCost = MUSHROOM_PRICE;
}
}
public static void main(String[] args)
{
JPizza aFrame =
new JPizza();
final int WIDTH = 300;
final int HEIGHT = 200;
aFrame.setSize(WIDTH, HEIGHT);
aFrame.setVisible(true);
}
}
以下是错误：
c:\Java\Homework\CH14\YouDoIt>javac JPizza.java
JPizza.java:31: error: <identifier> expected
pizzaSizeValue.addItem("Extra Large - $14");
^
JPizza.java:31: error: illegal start of type
pizzaSizeValue.addItem("Extra Large - $14");
^
JPizza.java:32: error: <identifier> expected
pizzaSizeValue.addItem("Large - $11");
^
JPizza.java:32: error: illegal start of type
pizzaSizeValue.addItem("Large - $11");
^
JPizza.java:33: error: <identifier> expected
pizzaSizeValue.addItem("Medium - $9");
^
JPizza.java:33: error: illegal start of type
pizzaSizeValue.addItem("Medium - $9");
^
JPizza.java:34: error: <identifier> expected
pizzaSizeValue.addItem("Small - $7");
^
JPizza.java:34: error: illegal start of type
pizzaSizeValue.addItem("Small - $7");
^
JPizza.java:35: error: <identifier> expected
pizzaSizeValue.setSelectedItem("Extra Large - $14");
^
JPizza.java:35: error: illegal start of type
pizzaSizeValue.setSelectedItem("Extra Large - $14");
^
JPizza.java:39: error: <identifier> expected
pizzaToppingValue.addItem("Cheese - free");
^
JPizza.java:39: error: illegal start of type
pizzaToppingValue.addItem("Cheese - free");
^
JPizza.java:40: error: <identifier> expected
pizzaToppingValue.addItem("Pepperoni - $1");
^
JPizza.java:40: error: illegal start of type
pizzaToppingValue.addItem("Pepperoni - $1");
^
JPizza.java:41: error: <identifier> expected
pizzaToppingValue.addItem("Sausage - $1");
^
JPizza.java:41: error: illegal start of type
pizzaToppingValue.addItem("Sausage - $1");
^
JPizza.java:42: error: <identifier> expected
pizzaToppingValue.addItem("Red Onion - $1");
^
JPizza.java:42: error: illegal start of type
pizzaToppingValue.addItem("Red Onion - $1");
^
JPizza.java:43: error: <identifier> expected
pizzaToppingValue.addItem("Green Pepper - $1");
^
JPizza.java:43: error: illegal start of type
pizzaToppingValue.addItem("Green Pepper - $1");
^
JPizza.java:44: error: <identifier> expected
pizzaToppingValue.addItem("Mushroom - $1");
^
JPizza.java:44: error: illegal start of type
pizzaToppingValue.addItem("Mushroom - $1");
^
JPizza.java:45: error: <identifier> expected
pizzaToppingValue.setSelectedItem("Cheese - free");
^
JPizza.java:45: error: illegal start of type
pizzaToppingValue.setSelectedItem("Cheese - free");
^
24 errors
Any help would be appreciated!
答案 0 :(得分：0)
在任何构造函数或方法之外的类中，可以发现违规代码，并且它不存在。那里只能存在变量或类型声明和初始化。您的违规代码应该位于您班级的构造函数中。
请注意，此问题与JComboBoxes甚至Swing几乎没有关系，而且与您尝试对方法或构造函数之外的变量进行方法调用的常见Java问题有关。你可以在课堂上声明和初始化变量，但你不能在那里进行方法调用。