按钮在动作中未获得GUI Java计算器的输入]

Question

我正在尝试使用Java swing创建计算器，但是当我单击按钮时，似乎没有任何输出。

'''

  package com.company;

 import java.awt.BorderLayout;
 import java.awt.GridBagConstraints;
  import java.awt.GridBagLayout;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class Main implements ActionListener {
    private static JTextField inputBox;

 Main(){}
public static void main(String[] args) {
    createWindow();
}

private static void createWindow() {
    JFrame frame = new JFrame("Calculator");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    createUI(frame);
    frame.setSize(200, 200);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
}

public static void createUI(JFrame frame) {
    JPanel panel = new JPanel();
    Calculator c = new Calculator();
    GridBagLayout layout = new GridBagLayout();
    GridBagConstraints gbc = new GridBagConstraints();
    panel.setLayout(layout);

    inputBox = new JTextField(10);
    inputBox.setEditable(true);

    JButton button0 = new JButton("0");
    JButton button1 = new JButton("1");
    JButton button2 = new JButton("2");
    JButton button3 = new JButton("3");
    JButton button4 = new JButton("4");
    JButton button5 = new JButton("5");
    JButton button6 = new JButton("6");
    JButton button7 = new JButton("7");
    JButton button8 = new JButton("8");
    JButton button9 = new JButton("9");

    JButton buttonPlus = new JButton("+");
    JButton buttonMinus = new JButton("-");
    JButton buttonDivide = new JButton("/");
    JButton buttonMultiply = new JButton("*");
    JButton buttonClear = new JButton("Clear");
    JButton buttonDot = new JButton(".");
    JButton buttonEquals = new JButton("=");

    button1.addActionListener(c);
    button2.addActionListener(c);
    button3.addActionListener(c);
    button4.addActionListener(c);
    button5.addActionListener(c);
    button6.addActionListener(c);
    button7.addActionListener(c);
    button8.addActionListener(c);
    button9.addActionListener(c);
    button0.addActionListener(c);

    buttonPlus.addActionListener(c);
    buttonMinus.addActionListener(c);
    buttonDivide.addActionListener(c);
    buttonMultiply.addActionListener(c);
    buttonClear.addActionListener(c);
    buttonDot.addActionListener(c);
    buttonEquals.addActionListener(c);

    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.gridx = 0; gbc.gridy = 0; panel.add(button1, gbc);
    gbc.gridx = 1; gbc.gridy = 0; panel.add(button2, gbc);
    gbc.gridx = 2; gbc.gridy = 0; panel.add(button3, gbc);
    gbc.gridx = 3; gbc.gridy = 0; panel.add(buttonPlus, gbc);
    gbc.gridx = 0; gbc.gridy = 1; panel.add(button4, gbc);
    gbc.gridx = 1; gbc.gridy = 1; panel.add(button5, gbc);
    gbc.gridx = 2; gbc.gridy = 1; panel.add(button6, gbc);
    gbc.gridx = 3; gbc.gridy = 1; panel.add(buttonMinus, gbc);
    gbc.gridx = 0; gbc.gridy = 2; panel.add(button7, gbc);
    gbc.gridx = 1; gbc.gridy = 2; panel.add(button8, gbc);
    gbc.gridx = 2; gbc.gridy = 2; panel.add(button9, gbc);
    gbc.gridx = 3; gbc.gridy = 2; panel.add(buttonDivide, gbc);
    gbc.gridx = 0; gbc.gridy = 3; panel.add(buttonDot, gbc);
    gbc.gridx = 1; gbc.gridy = 3; panel.add(button0, gbc);
    gbc.gridx = 2; gbc.gridy = 3; panel.add(buttonClear, gbc);
    gbc.gridx = 3; gbc.gridy = 3; panel.add(buttonMultiply, gbc);
    gbc.gridwidth = 3;

    gbc.gridx = 0;
    gbc.gridy = 4;
    panel.add(inputBox, gbc);
    gbc.gridx = 3;
    gbc.gridy = 4;
    panel.add(buttonEquals, gbc);
    frame.getContentPane().add(panel, BorderLayout.CENTER);
}

public void actionPerformed(ActionEvent e) {
     System.out.println(e);
    String command = e.getActionCommand();
    if (command.charAt(0) == 'C') {
        inputBox.setText("");
        System.out.println("");
    }else if (command.charAt(0) == '=') {
        inputBox.setText(evaluate(inputBox.getText()));
        System.out.println("equals");
    }else {
        inputBox.setText(inputBox.getText() + command);
        System.out.println("else3");
    }

}


public static String evaluate(String expression) {
    char[] arr = expression.toCharArray();
    String operand1 = "";
    String operand2 = "";
    String operator = "";
    double result = 0;

    for (int i = 0; i < arr.length; i++) {
        if (arr[i] >= '0' && arr[i] <= '9' || arr[i] == '.') {
            if(operator.isEmpty()){
                operand1 += arr[i];
            }else{
                operand2 += arr[i];
            }
        }

        if(arr[i] == '+' || arr[i] == '-' || arr[i] == '/' || arr[i] == '*') {
            operator += arr[i];
        }
    }

    if (operator.equals("+")) {
        result = (Double.parseDouble(operand1) + Double.parseDouble(operand2));
        System.out.println("plus");
    }
    else if (operator.equals("-")) {
        result = (Double.parseDouble(operand1) - Double.parseDouble(operand2));
    }
    else if (operator.equals("/")) {
        result = (Double.parseDouble(operand1) / Double.parseDouble(operand2));
    }
    else {
        result = (Double.parseDouble(operand1) * Double.parseDouble(operand2));
    }
    return operand1 + operator + operand2 + "=" +result;
}

}'''

我是Java的初学者，不太确定这里是什么问题。当我在actionPreformed方法中放置打印行时，它不返回任何内容。

你知道这是怎么了吗？

我正在尝试使用java swing创建一个计算器，但是当我单击按钮时，似乎没有任何输出。 '''包com.company;导入java.awt.BorderLayout;导入java.awt ....

Answer 1

Calculator c = new Calculator();
...
button1.addActionListener(c);