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所以我试图在一个类中创建一个变量，然后在另一个类中检索它......

一类是产品，另一类是数量，我需要从文本框中获取值，然后将项目的成本乘以数量。

无论如何，我都不是 Java 专家，我似乎无法让它发挥作用。

没有进一步的工作，这是我正在使用的代码：

超市类：

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.text.DecimalFormat;


public class SuperMarket extends JFrame
{
   private ProductPanel routine;       // A panel for routine charge check boxes
   private QuantityPanel nonRoutine;   // A panel for non-routine charges
   private JPanel buttonPanel;         // A panel for the buttons
   private JButton calcButton;         // Calculates everything
   private JButton exitButton;         // Exits the application

   public SuperMarket()
   {
      // Display a title.
      setTitle("Supermarket");

      // Specify what happens when the close button is clicked.
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      // Create a RoutinePanel object.
      routine = new ProductPanel();

      // Create a NonRoutinePanel object.
      nonRoutine = new QuantityPanel();

      // Build the panel that contains the buttons.
      buildButtonPanel();

      // Add the panels to the content pane.
      add(routine, BorderLayout.WEST);
      add(nonRoutine, BorderLayout.EAST);
      add(buttonPanel, BorderLayout.SOUTH);

      // Pack and display the window.
      pack();
      setVisible(true);
   }

   private void buildButtonPanel()
   {
      // Create a button to calculate the charges.
      calcButton = new JButton("Calculate 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);
   }

   private class CalcButtonListener implements ActionListener
   {

      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 = routine.getCharges();

         // Display the message.
         JOptionPane.showMessageDialog(null, "Total Charges: $" + 
                                             dollar.format(totalCharges));
      }
   }

   private class ExitButtonListener implements ActionListener
   {
      public void actionPerformed(ActionEvent e)
      {
         System.exit(0);
      }
   }

   public static void main(String[] args)
   {
      SuperMarket ja = new SuperMarket();
   }
}

ProductPanel 类

import java.awt.*;
import javax.swing.*;
import java.text.DecimalFormat;

public class ProductPanel extends JPanel
{
   // Named constants for charges
    private QuantityPanel nonRoutine;

   private final double BAKED_BEAN_CHARGE = 0.35;
   private final double CORNFLAKE_CHARGE = 1.75;
   private final double SUGAR_CHARGE = 0.75;
   private final double TEA_BAGS_CHARGE = 1.15;
   private final double INSTANT_COFFEE_CHARGE = 2.50;
   private final double BREAD_CHARGE = 1.25;
   private final double SAUSAGES_CHARGE = 1.30;
   private final double EGGS_CHARGE = 1.30;
   private final double MILK_CHARGE = 1.30;
   private final double POTATOES_CHARGE = 1.30;

   private JCheckBox bakedBean;     // Check box for oil change
   private JCheckBox cornFlake;       // Check box for lube job
   private JCheckBox sugar; // Check box for radiator flush
   private JCheckBox teaBags;    // Check box for transmission flush
   private JCheckBox instantCoffee;    // Check box for inspection
   private JCheckBox bread;       // Check box for muffler replacement
   private JCheckBox sausages;  // Check box for tire rotation
   private JCheckBox eggs;  // Check box for tire rotation
   private JCheckBox milk;  // Check box for tire rotation
   private JCheckBox potatoes;  // Check box for tire rotation

   /**
      Constructor
   */

   public ProductPanel()
   {
      // Create a DecimalFormat object.
      DecimalFormat dollar = new DecimalFormat("#,##0.00");

      // Create the check boxes.
      bakedBean = new JCheckBox("Baked Beans ($" +
                                dollar.format(BAKED_BEAN_CHARGE) + ")");
      cornFlake = new JCheckBox("Cornflakes ($" +
                              dollar.format(CORNFLAKE_CHARGE) + ")");
      sugar = new JCheckBox("Sugar ($" + 
                                    dollar.format(SUGAR_CHARGE) + ")");
      teaBags = new JCheckBox("Tea Bags ($" + 
                                 dollar.format(TEA_BAGS_CHARGE) + ")");
      instantCoffee = new JCheckBox("Instant Coffee ($" + 
                                 dollar.format(INSTANT_COFFEE_CHARGE) + ")");
      bread = new JCheckBox("Bread ($" + 
                              dollar.format(BREAD_CHARGE) + ")");
      sausages = new JCheckBox("Sausages ($" + 
              dollar.format(SAUSAGES_CHARGE) + ")");

      eggs = new JCheckBox("Eggs ($" + 
              dollar.format(EGGS_CHARGE) + ")");

      milk = new JCheckBox("Milk ($" + 
              dollar.format(MILK_CHARGE) + ")");

      potatoes = new JCheckBox("Potatoes ($" + 
              dollar.format(POTATOES_CHARGE) + ")");

      // Create a GridLayout manager.
      setLayout(new GridLayout(10, 1));

      // Create a border.
      setBorder(BorderFactory.createTitledBorder("Food Product"));

      // Add the check boxes to this panel.
      add(bakedBean);
      add(cornFlake);
      add(sugar);
      add(teaBags);
      add(instantCoffee);
      add(bread);
      add(sausages);
      add(eggs);
      add(milk);
      add(potatoes);
   }

   /**
      The getCharges method calculates the routine charges.
      @return The amount of routine charges.
   */

   public double getCharges()
   {
      double charges = 0;

      if (bakedBean.isSelected())
          charges += BAKED_BEAN_CHARGE * 1;
      if (cornFlake.isSelected())
         charges += CORNFLAKE_CHARGE;
      if (sugar.isSelected())
         charges += SUGAR_CHARGE;
      if (teaBags.isSelected())
         charges += TEA_BAGS_CHARGE;
      if (instantCoffee.isSelected())
         charges += INSTANT_COFFEE_CHARGE;
      if (bread.isSelected())
         charges += BREAD_CHARGE;
      if (sausages.isSelected())
          charges += SAUSAGES_CHARGE;
      if (eggs.isSelected())
          charges += EGGS_CHARGE;
      if (milk.isSelected())
          charges += MILK_CHARGE;
      if (potatoes.isSelected())
          charges += POTATOES_CHARGE;

      return charges;
   }
}

数量面板类

import java.awt.*;
import javax.swing.*;


public class QuantityPanel extends JPanel
{   
   public JTextField beans;  // Parts charges
   private JTextField cornFlakes;  // Hours of labor
   private JTextField sugar;  // Hours of labor
   private JTextField teaBags;  // Hours of labor
   private JTextField instantCoffee;  // Hours of labor
   private JTextField bread;  // Hours of labor
   private JTextField sausages;  // Hours of labor
   private JTextField eggs;  // Hours of labor
   private JTextField milk;  // Hours of labor
   private JTextField potatoes;  // Hours of labor

   public QuantityPanel()
   {
      beans = new JTextField("0", 4);
      double beanQuantity = Double.parseDouble(beans.getText());
      cornFlakes = new JTextField("0", 4);
      sugar = new JTextField("0", 4);
      teaBags = new JTextField("0", 4);
      instantCoffee = new JTextField("0", 4);
      bread = new JTextField("0", 4);
      sausages = new JTextField("0", 4);
      eggs = new JTextField("0", 4);
      milk = new JTextField("0", 4);
      potatoes = new JTextField("0", 4);


      // Create a GridLayout manager.
      setLayout(new GridLayout(10, 1));

      // Create a border.
      setBorder(BorderFactory.createTitledBorder("Quantity"));

      // Add the labels and text fields to this panel.
      add(beans);
      add(cornFlakes);
      add(sugar);
      add(teaBags);
      add(instantCoffee);
      add(bread);
      add(sausages);
      add(eggs);
      add(milk);
      add(potatoes);
   }
}

正如您在 Quantity 类上看到的那样，我尝试创建一个从文本字段获取值的双精度数，并且我尝试在可以看到 BAKED_BEAN_CHARGE * 1 的地方检索它，但是我需要的是 * 1 而不是用户文本字段输入。

任何帮助表示赞赏，欢呼。

4

2 回答 2

2

这里的问题是范围：您正在构造函数中创建一个新变量。

在构造函数之外获取双 beanQuantity 声明，然后使用文本字段输入对其进行初始化。

将您的 beanQuantity 作为类变量，您可以创建一个方法来在需要时随时返回它（getter）。

您可以private double beanQuantity;在最后一个 JTextField 正下方调用它，然后创建一个方法public double getBeanQuantity() { return beanQuantity; } ，只需确保在您的构造函数中删除双关键字

于 2013-03-29T14:15:02.757 回答
1

首先，您需要将您的 QuantityPanel 传递到您的 ProductPanel 构造函数中，以便您可以设置您拥有存根的成员变量。为此，请更改您的 SuperMarket 构造函数：

  // Create a NonRoutinePanel object.
  nonRoutine = new QuantityPanel();

  // Create a RoutinePanel object.
  routine = new ProductPanel( nonRoutine );

然后像这样修改 ProductPanel 中的构造函数：

public ProductPanel( QuantityPanel nonRoutine ) {
    this.nonRoutine = nonRoutine;
    ...

您需要移动此行：

double beanQuantity = Double.parseDouble(beans.getText());

到一个方法：

public double getBeanQuantity() {
    return Double.parseDouble( beans.getText() );
}

然后在您的产品面板中，您可以这样使用它：

...
if (bakedBean.isSelected())
    charges += BAKED_BEAN_CHARGE * nonRoutine.getBeanQuantity();
...
于 2013-03-29T14:16:58.970 回答