如何制作。在计算器中的按钮

Question

我是Java的新手，我一直在尝试创建一个计算器。我已经把一切都搞定了，除了。按钮，任何人都可以帮我弄清楚如何做到这一点，我已经尝试了我所知道的一切，但没有任何作用

这是我到目前为止的代码：

package Java24;

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

public class Calculator extends JFrame implements ActionListener{

    JPanel row1 = new JPanel();
    JTextField display = new JTextField("0");
    Font font = new Font("Calibri", Font.PLAIN, 24);

    JPanel row2 = new JPanel();
    JButton c = new JButton("C");

    JPanel row3 = new JPanel();
    JButton num7 = new JButton("7");
    JButton num8 = new JButton("8");
    JButton num9 = new JButton("9");
    JButton divide = new JButton("/");

    JPanel row4 = new JPanel();
    JButton num4 = new JButton("4");
    JButton num5 = new JButton("5");
    JButton num6 = new JButton("6");
    JButton multiply = new JButton("*");

    JPanel row5 = new JPanel();
    JButton num1 = new JButton("1");
    JButton num2 = new JButton("2");
    JButton num3 = new JButton("3");
    JButton minus = new JButton("-");

    JPanel row6 = new JPanel();
    JButton num0 = new JButton("0");
    JButton dot = new JButton(".");
    JButton equals = new JButton("=");
    JButton plus = new JButton("+");

    public Calculator(){
    super("Calculator");
    setSize(450,350);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    GridLayout layout = new GridLayout(6,1);
    setLayout(layout);

    GridLayout layout1 = new GridLayout(1,1);
    display.setFont(font);
    display.setEnabled(false);
    row1.setLayout(layout1);
    row1.add(display);
    add(row1);

    c.addActionListener(this);
    c.setFont(font);
    row2.setLayout(layout1);
    row2.add(c);
    add(row2);

    num7.setFont(font);
    num8.setFont(font);
    num9.setFont(font);
    divide.setFont(font);
    num7.addActionListener(this);
    num8.addActionListener(this);
    num9.addActionListener(this);
    divide.addActionListener(this);
    GridLayout layout2 = new GridLayout(1,4);
    row3.setLayout(layout2);
    row3.add(num7);
    row3.add(num8);
    row3.add(num9);
    row3.add(divide);
    add(row3);

    num4.setFont(font);
    num5.setFont(font);
    num6.setFont(font);
    multiply.setFont(font);
    num4.addActionListener(this);
    num5.addActionListener(this);
    num6.addActionListener(this);
    multiply.addActionListener(this);
    row4.setLayout(layout2);
    row4.add(num4);
    row4.add(num5);
    row4.add(num6);
    row4.add(multiply);
    add(row4);

    num1.setFont(font);
    num2.setFont(font);
    num3.setFont(font);
    minus.setFont(font);
    num1.addActionListener(this);
    num2.addActionListener(this);
    num3.addActionListener(this);
    minus.addActionListener(this);
    row5.setLayout(layout2);
    row5.add(num1);
    row5.add(num2);
    row5.add(num3);
    row5.add(minus);
    add(row5);

    num0.setFont(font);
    dot.setFont(font);
    equals.setFont(font);
    plus.setFont(font);
    num0.addActionListener(this);
    dot.addActionListener(this);
    equals.addActionListener(this);
    plus.addActionListener(this);
    row6.setLayout(layout2);
    row6.add(num0);
    row6.add(dot);
    row6.add(equals);
    row6.add(plus);
    add(row6);

    setVisible(true);
    }

    public void actionPerformed(ActionEvent e){
        String button = e.getActionCommand();
        if(button.equals("C")){
            display.setText("0");
        }
        if(button.equals("7")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 7;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 7;
                display.setText("" + num);
            }
        }
        if(button.equals("8")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 8;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 8;
                display.setText("" + num);
            }
        }
        if(button.equals("9")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 9;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 9;
                display.setText("" + num);
            }
        }
        if(button.equals("4")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 4;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 4;
                display.setText("" + num);
            }
        }
        if(button.equals("5")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 5;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 5;
                display.setText("" + num);
            }
        }
        if(button.equals("6")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 6;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 6;
                display.setText("" + num);
            }
        }
        if(button.equals("1")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 1;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 1;
                display.setText("" + num);
            }
        }
        if(button.equals("2")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 2;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 2;
                display.setText("" + num);
            }
        }
        if(button.equals("3")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 3;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 3;
                display.setText("" + num);
            }
        }
        if(button.equals("0")){
            int lol = Integer.parseInt(display.getText());
            if(lol != 0){
                int num = 0;
                int prevNum = Integer.parseInt(display.getText());
                display.setText("" + prevNum + num);
            }else{
                int num = 0;
                display.setText("" + num);
            }
        }
        if(button.equals("+")){
            plus();
        }
        if(button.equals("-")){
            minus();
        }
        if(button.equals("*")){
            multiply();
        }
        if(button.equals("/")){
            divide();
        }
        if(button.equals("=")){
            if(plusNum != null){
                int secondNum = Integer.parseInt(display.getText());
                int sum = firstNum + secondNum;
                String secondNumber = String.valueOf(secondNum);
                display.setText("" + sum);
                if(plusNum != null){
                    remove(plusNum);
                }
                if(minusNum != null){
                    remove(minusNum);
                }
                if(multiplyNum != null){
                    remove(multiplyNum);
                }
                if(divideNum != null){
                    remove(divideNum);
                }                
                datNum = new JLabel(secondNumber);
                add(datNum);
                }
            if(minusNum != null){
                int secondNum = Integer.parseInt(display.getText());
                int sum = firstNum - secondNum;
                String secondNumber = String.valueOf(secondNum);
                display.setText("" + sum);
                if(plusNum != null){
                    remove(plusNum);
                }
                if(minusNum != null){
                    remove(minusNum);
                }
                if(multiplyNum != null){
                    remove(multiplyNum);
                }
                if(divideNum != null){
                    remove(divideNum);
                }
                datNum = new JLabel(secondNumber);
                add(datNum);
            }
            if(multiplyNum != null){
                int secondNum = Integer.parseInt(display.getText());
                int sum = firstNum * secondNum;
                String secondNumber = String.valueOf(secondNum);
                display.setText("" + sum);
                if(plusNum != null){
                    remove(plusNum);
                }
                if(minusNum != null){
                    remove(minusNum);
                }
                if(multiplyNum != null){
                    remove(multiplyNum);
                }
                if(divideNum != null){
                    remove(divideNum);
                }
                datNum = new JLabel(secondNumber);
                add(datNum);
            }
            if(divideNum != null){
                int secondNum = Integer.parseInt(display.getText());
                int sum = firstNum / secondNum;
                String secondNumber = String.valueOf(secondNum);
                display.setText("" + sum);
                if(plusNum != null){
                    remove(plusNum);
                }
                if(minusNum != null){
                    remove(minusNum);
                }
                if(multiplyNum != null){
                    remove(multiplyNum);
                }
                if(divideNum != null){
                    remove(divideNum);
                }
                datNum = new JLabel(secondNumber);
                add(datNum);
            }
        }
    }

    int firstNum;
    JLabel plusNum;
    JLabel minusNum;
    JLabel multiplyNum;
    JLabel divideNum;

    JLabel datNum;

    void plus(){
        firstNum = Integer.parseInt(display.getText());
        String firstNumber = String.valueOf(firstNum);
        if(minusNum != null){
           minusNum = null;
        }
        if(multiplyNum != null){
           multiplyNum = null;
        }
        if(divideNum != null){
            divideNum = null;
        }
        plusNum = new JLabel(firstNumber);
        add(plusNum);
        display.setText("0");     
    }

    void minus(){
        firstNum = Integer.parseInt(display.getText());
        String firstNumber = String.valueOf(firstNum);
        if(plusNum != null){
            plusNum = null;
        }
        if(multiplyNum != null){
            multiplyNum = null;
        }
        if(divideNum != null){
            divideNum = null;
        }
        minusNum = new JLabel(firstNumber);
        add(minusNum);
        display.setText("0");     
    }

    void multiply(){
        firstNum = Integer.parseInt(display.getText());
        String firstNumber = String.valueOf(firstNum);
        if(plusNum != null){
            plusNum = null;
        }
        if(minusNum != null){
            minusNum = null;
        }
        if(divideNum != null){
            divideNum = null;
        }
        multiplyNum = new JLabel(firstNumber);
        add(multiplyNum);
        display.setText("0");     
    }

    void divide(){
        firstNum = Integer.parseInt(display.getText());
        String firstNumber = String.valueOf(firstNum);
        if(plusNum != null){
            plusNum = null;
        }
        if(minusNum != null){
            minusNum = null;
        }
        if(multiplyNum != null){
            multiplyNum = null;
        }
        divideNum = new JLabel(firstNumber);
        add(divideNum);
        display.setText("0");     
    }

    public static void main(String[] args){
        Calculator calc = new Calculator();
    }
}

Answer 1

有些事情......

if(button.equals(".")){
    if(display.getText().indexOf('.') < 0 ){
        display.setText(display.getText() + ".");
    }else{
        //raise error
    }
}

另外，请务必将所有其他人从Double.parseDouble更改为Integer.parseInt ...有意义吗？