在求解 X 时从 JTextArea 检索双精度

Question

好吧，我对java有点陌生。我正在制作一个求解一步方程的程序。不过，我在运行它时遇到了一些困难。这是我的主文件的代码，Main.java：

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Main extends JFrame implements ActionListener {
    private static final long serialVersionUID = 1L;
    Solve solve = new Solve();
    JButton add = new JButton("Add");
    JButton sub = new JButton("Subtract");
    JButton mult = new JButton("Multiply");
    JButton div = new JButton("Divide");
    JButton solv = new JButton("Solve!");
    JTextArea one = new JTextArea();
    JLabel two = new JLabel(" = ");
    JLabel three = new JLabel("X");
    JLabel four = new JLabel();
    JTextArea five = new JTextArea();
    JLabel solved = new JLabel();
    JPanel row1 = new JPanel();
    JPanel row2 = new JPanel();
    JPanel row3 = new JPanel();
    public double funct;
    public Main() {
        super("Solving a one step equation!");
        setSize(500, 500);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        GridLayout layout = new GridLayout();
        setLayout(layout);
        FlowLayout layout1 = new FlowLayout(FlowLayout.CENTER);
        row1.setLayout(layout1);
        row1.add(add);
        row1.add(sub);
        row1.add(mult);
        row1.add(div);
        row1.add(solv);
        add(row1);
        add.addActionListener(this);
        sub.addActionListener(this);
        mult.addActionListener(this);
        div.addActionListener(this);
        solv.addActionListener(this);
        GridLayout layout2 = new GridLayout(1, 1, 1, 1);
        row2.setLayout(layout2);
        row2.add(one, BorderLayout.CENTER);
        row2.add(two, BorderLayout.CENTER);
        row2.add(three, BorderLayout.CENTER);
        row2.add(four, BorderLayout.CENTER);
        row2.add(five);
        add(row2, BorderLayout.CENTER);
        GridLayout layout3 = new GridLayout(5, 5, 5, 5);
        row3.setLayout(layout3);
        row3.add(solved);
        add(row3);
    }
    public static void main(String[] args) {
        Main frame = new Main();
    }
    public void actionPerformed(ActionEvent evt) {
        Object source = evt.getSource();
        if(source == add)
        {
            four.setText(" + ");
            funct = 1;
        }
        else if(source == sub)
        {
            four.setText(" - ");
            funct = 2;
        }
        else if(source == mult)
        {
            four.setText(" * ");
            funct = 3;
        }
        else if(source == div)
        {
            four.setText(" / ");
            funct = 4;
        }
        if(source == solv)
        {
            if(funct == 1)
            {
                double Ones = Double.parseDouble(three.getText());
                double Twos = Double.parseDouble(three.getText());
                solved.setText("X = " + solve.Add(Ones, Twos));
            }
            else if(funct == 2)
            {
                double Ones = Double.parseDouble(three.getText());
                double Twos = Double.parseDouble(three.getText());
                solved.setText("X = " + solve.Sub(Ones, Twos));
            }
            else if(funct == 3)
            {
                double Ones = Double.parseDouble(three.getText());
                double Twos = Double.parseDouble(three.getText());
                solved.setText("X = " + solve.Mult(Ones, Twos));
            }
            else if(funct == 4)
            {
                double Ones = Double.parseDouble(three.getText());
                double Twos = Double.parseDouble(three.getText());
                solved.setText("X = " + solve.Div(Ones, Twos));
            }
        }
    }
}

这是我的另一个文件Solve的代码.java

public class Solve {
    public double Add(double One, double Two)
    {
        return One - Two;
    }
    public double Sub(double One, double Two)
    {
        return One + Two;
    }
    public double Mult(double One, double Two)
    {
        return One / Two;
    }
    public double Div(double One, double Two)
    {
        return One * Two;
    }
}

一些帮助将不胜感激。有人看到我做错了什么吗？

Answer 1

单击

"解决"按钮后，您将获得NumberFormatException。这似乎是一个复制/粘贴问题 - 您没有检索到正确的数字。您正在尝试将"X"字符串转换为双精度。最好为变量指定有意义的名称。要修复异常，请尝试此操作，替换：

double Ones = Double.parseDouble(three.getText());
double Twos = Double.parseDouble(three.getText());

跟：

double Ones = Double.parseDouble(one.getText());
double Twos = Double.parseDouble(five.getText());

熟悉 Java 代码约定，特别是命名约定部分。

Answer 2

除了@Max的有用答案外，这里还有一些其他建议：

• 将框架的布局设置为 new GridLayout() 默认为不带填充的单行和单列。作为替代方法，请考虑 new GridLayout(0, 1, 5, 5) ，它会在具有 5x5 填充的列中生成任意数量的行。然后，您可以专注于每行的布局：

  row1.setLayout(new FlowLayout(FlowLayout.CENTER));
  row2.setLayout(new FlowLayout(FlowLayout.CENTER));
  row3.setLayout(new GridLayout(1, 1, 5, 5));
  

• 将setVisible()调用移动到帧构造函数的末尾：

  pack();
  setLocationRelativeTo(null);
  setVisible(true);
  

• 请考虑getRootPane().setDefaultButton(solv)将"解决"按钮设置为默认值。

• 请考虑将添加设置为默认值：

  private JLabel four = new JLabel("+");
  private int funct = 1; // add by default
  

• 考虑使用JTextField进行号码输入：

  private JTextField one = new JTextField(10);
  private JTextField five = new JTextField(10);