Grocery_shop
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.text.DecimalFormat;
/**
Grocery shop class
*/
public class Grocery_shop extends JFrame
{
private quantitypanel qty; // A panel for quantity
private Grocery_items items; // A panel for routine charge checkboxes
private JPanel buttonPanel; // A panel for the buttons
private JButton calcButton; // Calculates everything
private JButton exitButton; // Exits the application
private invoiceClass invoice;
/**
Constructor
*/
public Grocery_shop()
{
// Display a title.
setTitle("Victor's Grocery Shop");
// Specify what happens when the close button is clicked.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a NonRoutinePanel object.
qty = new quantitypanel();
// qty.setBackground(Color.white);
// Create a RoutinePanel object.
items = new Grocery_items( qty );
// Build the panel that contains the buttons.
buildButtonPanel();
// Add the panels to the content pane.
add(items, BorderLayout.WEST);
add(qty, BorderLayout.EAST);
add(buttonPanel, BorderLayout.SOUTH);
// Pack and display the window.
pack();
setVisible(true);
}
/**
The buildButtonPanel method creates a panel containing
buttons.
*/
private void buildButtonPanel()
{
// Create a button to calculate the charges.
calcButton = new JButton("Add Charges");
// Add an action listener to the button.
calcButton.addActionListener(new CalcButtonListener());
// Create a button to exit the application.
exitButton = new JButton("Exit");
// Add an action listener to the button.
exitButton.addActionListener(new ExitButtonListener());
// Put the buttons in their own panel.
buttonPanel = new JPanel();
buttonPanel.add(calcButton);
buttonPanel.add(exitButton);
}
/**
CalcButtonListener is an action listener class for the
calcButton component.
*/
private class CalcButtonListener implements ActionListener
{
/**
actionPerformed method
@param e An ActionEvent object.
*/
public void actionPerformed(ActionEvent e)
{
double totalCharges; // Total charges
// Create a DecimalFormat object to format output.
DecimalFormat dollar = new DecimalFormat("#,##0.00");
// Calculate the total charges
totalCharges = items.getCharges();
//+ nonRoutine.getCharges();
// Display the message.
JOptionPane.showMessageDialog(null, "Total Charges: $" +
dollar.format(totalCharges));
invoice = new invoiceClass();
invoice.getClass();
}
} // End of inner class
/**
ExitButtonListener is an action listener class for the
exitButton component.
*/
private class ExitButtonListener implements ActionListener
{
/**
actionPerformed method
@param e An ActionEvent object.
*/
public void actionPerformed(ActionEvent e)
{
System.exit(0);
}
} // End of inner class
/**
The main method creates an instance of the JoesAutomotive
class, causing it to display its window.
*/
public static void main(String[] args)
{
Grocery_shop grocery = new Grocery_shop();
}
}
Grocery_items
import java.awt.*;
import javax.swing.*;
import java.text.DecimalFormat;
/**
RoutinePanel class
*/
public class Grocery_items extends JPanel
{
// Named constants for charges
private final double Baked_Beans = 0.35;
private final double Cornflakes = 1.75;
private final double Sugar = 0.75;
private final double Tea_Bags = 1.15;
private final double Instant_Coffee = 2.50;
private final double Bread = 1.25;
private final double Sausage = 1.30;
private final double Eggs = 0.75;
private final double Milk = 0.65;
private final double Potatoes = 2.00;
private quantitypanel qty; // A panel for quantity
private JCheckBox baked_beans_box; // Check box for baked_beans
private JCheckBox CornflakesBox; // Check box for cornflakes
private JCheckBox SugarBox; // Check box for sugar box
private JCheckBox Tea_Bags_Box; // Check box for tea bag
private JCheckBox Instant_Coffee_Box; // Check box for Instant_Coffee_Box
private JCheckBox Bread_Box; // Check box for bread box
private JCheckBox SausageBox; // Check box for sausage box
private JCheckBox eggbox; // Check box for egg box
private JCheckBox milkbox; // Check box for milk
private JCheckBox potatoesbox; // Check box for potatoes
// private JTextField baked_beans_JT;
/**
Constructor
*/
public Grocery_items(quantitypanel qty)
{
this.qty = qty;
DecimalFormat dollar = new DecimalFormat("#,##0.00");
// Create the check boxes.
baked_beans_box = new JCheckBox("Baked_Beans ($" +
dollar.format(Baked_Beans) + ")");
CornflakesBox = new JCheckBox("Cornflakes ($" +
dollar.format(Cornflakes) + ")");
SugarBox = new JCheckBox("Sugar ($" +
dollar.format(Sugar) + ")");
Tea_Bags_Box = new JCheckBox("Tea Bags ($" +
dollar.format(Tea_Bags) + ")");
Instant_Coffee_Box = new JCheckBox("Instant Coffee_Box ($" +
dollar.format(Instant_Coffee) + ")");
Bread_Box = new JCheckBox("Bread Box ($" +
dollar.format(Bread) + ")");
SausageBox = new JCheckBox("Suasages ($" +
dollar.format(Sausage) + ")");
eggbox = new JCheckBox("Eggs ($" +
dollar.format(Eggs) + ")");
milkbox = new JCheckBox("Milk ($" +
dollar.format(Milk) + ")");
potatoesbox = new JCheckBox("Potatoes ($" +
dollar.format(Potatoes) + ")");
// Create a GridLayout manager.
setLayout(new GridLayout(10, 1));
// Create a border.
setBorder(BorderFactory.createTitledBorder("Grocery Items"));
// Add the check boxes to this panel.
add(baked_beans_box);
add(CornflakesBox);
add(SugarBox);
add(Tea_Bags_Box);
add(Instant_Coffee_Box);
add(Bread_Box);
add(SausageBox);
add(eggbox);
add(milkbox);
add(potatoesbox);
}
/**
The getCharges method calculates the routine charges.
@return The amount of routine charges.
*/
public double getCharges()
{
double charges = 0;
if (baked_beans_box.isSelected())
charges += Baked_Beans * qty.getBeanqty();
if (CornflakesBox.isSelected())
charges += Cornflakes;
if (SugarBox.isSelected())
charges += Sugar;
if (Tea_Bags_Box.isSelected())
charges += Tea_Bags;
if (Instant_Coffee_Box.isSelected())
charges += Instant_Coffee;
if (Bread_Box.isSelected())
charges += Bread;
if (SausageBox.isSelected())
charges += Sausage;
if (eggbox.isSelected())
charges += Eggs;
if (milkbox.isSelected())
charges += Milk;
if (potatoesbox.isSelected())
charges += Potatoes;
return charges;
}
}
quantitypanel
//import java.awt.LayoutManager;
import java.awt.GridLayout;
//import javax.swing.JCheckBox;
//import javax.swing.JLabel;
import javax.swing.BorderFactory;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class quantitypanel extends JPanel {
private JTextField baked_beans_JT; // JTextField box for baked_beans
private JTextField Cornflakes_JT; // JTextField box for cornflakes
private JTextField Sugar_JT; // JTextField box for sugar box
private JTextField Tea_Bags_JT; // JTextField box for tea bag
private JTextField Instant_Coffee_JT; // JTextField box for Instant_Coffee_Box
private JTextField Bread_JT; // JTextField box for bread box
private JTextField Sausage_JT; // JTextField box for sausage box
private JTextField egg_JT; // JTextField box for egg box
private JTextField milk_JT; // JTextField box for milk
private JTextField potatoes_JT; // JTextField box for potatoes
public quantitypanel()
{
//create JTextField.
baked_beans_JT = new JTextField(5);
Cornflakes_JT = new JTextField(5);
Sugar_JT = new JTextField(5);
Tea_Bags_JT = new JTextField(5);
Instant_Coffee_JT = new JTextField(5);
Bread_JT = new JTextField(5);
Sausage_JT = new JTextField(5);
egg_JT = new JTextField(5);
milk_JT = new JTextField(5);
potatoes_JT = new JTextField(5);
//initialize text field to 0
baked_beans_JT.setText("0");
Cornflakes_JT.setText("0");
Sugar_JT.setText("0");
Tea_Bags_JT.setText("0");
Instant_Coffee_JT.setText("0");
Bread_JT.setText("0");
Sausage_JT.setText("0");
egg_JT.setText("0");
milk_JT.setText("0");
potatoes_JT.setText("0");
//set Layout manager
setLayout(new GridLayout(10, 1));
//create border and panel title
setBorder(BorderFactory.createTitledBorder("Amount"));
//add text fields to the panel.
add(baked_beans_JT);
add(Cornflakes_JT);
add(Sugar_JT);
add(Tea_Bags_JT);
add(Instant_Coffee_JT);
add(Bread_JT);
add(Sausage_JT);
add(egg_JT);
add(milk_JT);
add(potatoes_JT);
}
public double getBeanqty()
{
try
{
return Double.parseDouble(baked_beans_JT.getText());
}
catch(NumberFormatException ev){
JOptionPane.showMessageDialog(null, "invalid");
}
return 0;
}
}
invoiceClass
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.text.DecimalFormat;
public class invoiceClass {
private Grocery_items items;
private quantitypanel qty; // A panel for quantity
{
double total; // Total charges
DecimalFormat dollar = new DecimalFormat("#,##0.00");
qty = new quantitypanel();
items = new Grocery_items(qty);
// Calculate the total charges
double payment = 0.0;
String input;
input = JOptionPane.showInputDialog(null, "enter a your payment");
payment = Double.parseDouble(input);
total = payment - items.getCharges();
JOptionPane.showMessageDialog(null, "your change is: " + total);
}
}
请使用上面的代码，我正在尝试为该程序制作收据。
我想在此代码total = payment - items.getCharges();中让系统获取总费用并从用户输入的数字中减去它。在这种情况下，系统仅识别付款。
请帮助..
感谢
答案 0 :(得分：1)
items.getCharges()返回0的原因是每次invoiceClass CalcButtonListener发生时都会创建一个新的Action实例。这会创建一个新的Grocery_items实例。
反过来，这会创建新的GUI元素，包括复选框。这些复选框不是应用程序中可见的复选框，因为它们尚未添加。现在，当您致电getCharges时，新创建的JCheckBoxes上Grocery_items的选择状态将为false（默认状态为JCheckBox），因此不会将收取费用
public double getCharges() {
double charges = 0;
if (baked_beans_box.isSelected()) // now false!
charges += Baked_Beans * qty.getBeanqty();
if (...)
因此，解决方案不是在Grocery_items中创建quantitypanel，而是使用原始实例。
除此之外：使用Java命名约定的类以大写开头，例如QuantityPanel。通常不使用下划线，例如GroceryItems