Question

我正在尝试创建一个允许用户选择项目的程序。选择项目后，将出现一个包含总价格成本的框。当我运行该程序时，我点击了一个项目，结果显示为否定。似乎我的if和else语句是错误的，我只是无法找到如何正确修复它。

package javaapplication118;

import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextField;

public class pizza extends JFrame {

JTextField textField, priceField;
JCheckBox pineApple, drink, delivery, meatballs;
JButton button;

pizza() {

    super("Pizza order");
    setLayout(new FlowLayout());

    textField = new JTextField("hello please check anything you would like to order");
    textField.setEditable(false);
    textField.setBackground(Color.yellow);
    add(textField);


    EventHandler handler = new EventHandler();
    pineApple = new JCheckBox("Pine apples");
    pineApple.addItemListener(handler);
    add(pineApple);

    drink = new JCheckBox("drink");
    drink.addItemListener(handler);
    add(drink);

    delivery = new JCheckBox("delivery");
    delivery.addItemListener(handler);
    add(delivery);

    meatballs = new JCheckBox("meat balls");
    meatballs.addItemListener(handler);
    add(meatballs);

    priceField = new JTextField("$", 15);

    add(priceField);


    button = new JButton("confirm order");
    button.addActionListener(
            new ActionListener() {
        public void actionPerformed(ActionEvent event) {

            JOptionPane.showMessageDialog(null, "Your order has been placed.");



        }
       });
       add(button);


   }
   //JTextField textField priceField 
  // JCheckBox pineApple, drink, delivery, meatballs; 

   public class EventHandler implements ItemListener {

    double price = 0;

    public void itemStateChanged(ItemEvent event) {

        if (pineApple.isSelected()) {  // if pineapple is selected add to the price

            price = price + 2.30;

        } else if (!pineApple.isSelected()){ // if pineapple is deselected subtract from price
            price = price - 2.30;

        }
         if (delivery.isSelected()) {

            price = price + 5;

        } else if (!delivery.isSelected()) {

            price = price - 5;

        }
         if (drink.isSelected()) {

            price = price + 1;

        } else if (!drink.isSelected()) {

            price = price - 1;

        }
         if (meatballs.isSelected()) {

            price = price + 1;

        } else if (!meatballs.isSelected()) {

            price = price - 1;

        }



        priceField.setText("$" + price);

    }
   }
 }

Answer 1

您似乎“假设”过去选择了一件或多件物品，但您无法知道这是否属实......

相反，请将price重置为0，并仅为那些实际当前选中的项目添加price ...

public void itemStateChanged(ItemEvent event) {
    price = 0;
    if (pineApple.isSelected()) {
        price = price + 2.30;
    }
    if (delivery.isSelected()) {
        price = price + 5;
    }
    if (drink.isSelected()) {
        price = price + 1;
    }
    if (meatballs.isSelected()) {
        price = price + 1;
    }

    priceField.setText("$" + price);
}

Answer 2

您的代码会从价格中减去价值。那就是当你选择“肉丸”时它会加1价格，现在的价格是1.00美元然后清除其他复选框（您已编码，以便在清除复选框时减去相关值）

菠萝2.30美元，送餐费5美元，饮料1.00美元（总价8.30美元）从价格“减去”。

1 - 8.3 = -7.3

这就是你得到负值的原因。

我在gui程序中做错了什么？

2 个答案: