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我正在尝试为我正在学习的 Java 类创建一个 GUI 工资计算器。要求是它必须接受用户输入（使用 JComboBox），计算每周工资并将结果添加到 JTable。用户应该能够继续为其他员工计算并有一个退出按钮。我在主类中创建了 GUI，需要两个 ActionListener，一个用于退出，一个用于计算并添加到 JTable。

我的问题是，当我开始计算 ActionListener 时，它无法识别我在主类中设置的变量。我已经尝试将它们公开，使用主类名 DOT 变量名（PayrollCalc.empName），初始化它们，但似乎没有任何效果。代码不完整，因为在我可以先完成实际计算之前，我什至还没有开始添加到 JTable。有没有人有什么建议？

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

public class PayrollCalc {

    public static void main(String[] args) {

        //Declare variables used
        String empName = null, entDept = null, calcdPay = null;
        String[] empDept = {"Marketing","IT","Accounting","Development","Payroll","Facilities"};
        String columnNames[] = {"Name","Department","Pay Check"};
        String dataValues [][] = {
                {empName,entDept,calcdPay}
        };

        double wrkHours = 0;
        double empRate = 0;
        double wklyPay = 0;

        //Create JTable and scrollPane for output
        JTable table;
        JScrollPane scrollPane;
        table = new JTable (dataValues,columnNames);
        scrollPane = new JScrollPane(table);

        //Create JFrame object with title
        JFrame frame = new JFrame("Employee Payroll Calculator");

        //Create combo box for department choices
        JComboBox combo = new JComboBox(empDept);
        JTextField nameField = new JTextField(15);
        JTextField hourField = new JTextField(10);
        JTextField rateField = new JTextField(10);

        //Create JLables for input fields
        JLabel nameLbl = new JLabel ("Name:");
        JLabel hourLbl = new JLabel ("Hours:");
        JLabel rateLbl = new JLabel ("Rate:");
        JLabel deptLbl = new JLabel ("Department:");

        //Create buttons for ActionListners
        JButton exitButton= new JButton("Exit");
        exitButton.addActionListener(new exitApp());
        exitButton.setSize(5,5);

        JButton calcButton= new JButton("Calculate");
        calcButton.addActionListener(new calcApp());
        calcButton.setSize(5,5);

        //Create panels
        Panel panel1 = new Panel();
        panel1.add(nameLbl);
        panel1.add(nameField);
        panel1.add(deptLbl);
        panel1.add(combo);
        panel1.add(hourLbl);
        panel1.add(hourField);
        panel1.add(rateLbl);
        panel1.add(rateField);
        panel1.add(rateField);

        Panel panel2 = new Panel();
        panel2.add(calcButton);

        Panel panel3 = new Panel();
        panel3.add(calcButton);
        panel3.add(exitButton);

        Panel panel4 = new Panel();
        panel4.add(scrollPane, BorderLayout.CENTER);


        //creates the frame
        frame.setSize(950,200);
        frame.add(panel1,BorderLayout.NORTH);
        frame.add(panel2);
        frame.add(panel3, BorderLayout.SOUTH);
        frame.add(panel4);
        frame.setVisible(true);



    }
    //ActionListner for Exit button
    static class exitApp implements ActionListener
    {
        public void actionPerformed(ActionEvent e)
        {
            System.exit(0);
        }
    }
    //ActionListner for Calculate button
    static class calcApp implements ActionListener
    {
        public void actionPerformed(ActionEvent c)
        {
            empName = nameField.getText();
            entDept = combo.getName();
            wrkHours = Double.parseDouble(hourField.getText());
            empRate = Double.parseDouble(rateField.getText());
            wklyPay = wrkHours * empRate;
            calcdPay = new Double(wklyPay).toString();
        }

    }

}
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2 回答 2

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由于您尝试访问的变量对您来说ActionListener是本地的，main()因此它们对您的静态类不可见。此外，在静态 main()中初始化 GUI会强制在每个地方使用静态，正如您从下面的评论中可以看出的那样，这是一种不好的做法。

因此，将初始化移到构造函数和局部变量作为实例级成员字段。除此之外，您还需要从静态嵌套类切换到使用内部类。

然后，您的类的实例成员将可用于您的内部 ActionListener类。

public class PayrollCalc {

    //Declare variables used
    private String empName = null, entDept = null, calcdPay = null;

    private double wrkHours = 0;
    private double empRate = 0;
    private double wklyPay = 0;

    private JComboBox combo;
    private JTextField nameField;
    private JTextField hourField;
    private JTextField rateField;

    public static void main(String[] args) {
        new PayrollCalc();
    }

    public PayrollCalc() {
        // ...
        combo = new JComboBox(empDept);
        nameField = new JTextField(15);
        hourField = new JTextField(10);
        rateField = new JTextField(10);
        // ...
    }

    // non-static ActionListener inner classes
}
于 2013-07-05T16:14:04.023 回答
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看，每个变量都有它的作用域……你还没有将任何东西定义为成员类变量，所以没有任何东西可以充当全局变量。

you have defined variable inside main method () so their scope is limited to only main method这就是你的问题背后的原因。

于 2013-07-05T16:22:18.080 回答