简单java计算代码不能完全工作

作为Java初学者，我一直在创建一个计算器。我添加了一些功能更复杂的按钮，但由于某些原因，这些按钮无法正常工作

有人能告诉我为什么这些java计算不能正常工作吗？ 工作正常的按钮有加号、减号、乘号和除法。 工作不太好的按钮有百分比，平方米，以及PlusMinus按钮

您可以在计算器引擎中看到，我已经实现了正确的计算方法，但是当按下有问题的按钮时，计算器的文本显示区域变为空白，例如，如果在计算器上按64，然后按sqrt，则假定显示64的平方根，但不显示。提前谢谢你的帮助。（别紧张，我是初学者）

这是计算器

package Calculator;

import javax.swing.*;

import java.awt.GridLayout;
import java.awt.BorderLayout;

public class Calculator {

// Declare and instantiate window components
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 buttonPoint = new JButton(".");
JButton buttonEqual = new JButton("=");
JButton buttonPlus = new JButton("+");
JButton buttonMinus = new JButton("-");
JButton buttonDivide = new JButton("/");
JButton buttonMultiply = new JButton("*");
JButton buttonSquareRt = new JButton("sqrt");
JButton buttonPercentage = new JButton("%");
JButton buttonPlusMinus = new JButton("+/-");
JButton buttonClear = new JButton("C");


JPanel windowContent = new JPanel();
JTextField displayField = new JTextField(30);

// Constructor
Calculator() {

    // Set the layout manager for this panel

    BorderLayout bl = new BorderLayout();
    windowContent.setLayout(bl);

    // Add the display field to the top of the window

    windowContent.add("North", displayField);

    // Create the panel with the GridLayout
    // that will contain 12 buttons - 10 numeric ones, and
    // buttons with the point and the equal sign

    JPanel p1 = new JPanel();
    GridLayout gl = new GridLayout(4, 3);
    p1.setLayout(gl);

    p1.add(button1);
    p1.add(button2);
    p1.add(button3);
    p1.add(button4);
    p1.add(button5);
    p1.add(button6);
    p1.add(button7);
    p1.add(button8);
    p1.add(button9);
    p1.add(button0);
    p1.add(buttonPoint);
    p1.add(buttonEqual);

    // Add the panel p1 to the centre area of the window
    windowContent.add("Center", p1);

    // Create the panel with the GridLayout
    // that will contain 4 action buttons -
    // Plus, Minus, Divide and Multiply

    JPanel p2 = new JPanel();
    GridLayout gl2 = new GridLayout(4, 1);
    p2.setLayout(gl);
    p2.add(buttonPlus);
    p2.add(buttonMinus);
    p2.add(buttonMultiply);
    p2.add(buttonDivide);

    //adding the task buttons to go on extra column
    p2.add(buttonSquareRt);
    p2.add(buttonPercentage);
    p2.add(buttonPlusMinus);
    p2.add(buttonClear);

    // Add the panel p2 to the east area of the window
    windowContent.add("East", p2);


    // Create the frame and add the content pane to it
    JFrame frame = new JFrame("Calculator");

    frame.setContentPane(windowContent);

    // set the size of the window to be big enough to
    // accommodate all window controls

    frame.pack();

    // Display the window
    frame.setVisible(true);
    // Instantiate the event listener and

    // register each button with it

    CalculatorEngine calcEngine = new CalculatorEngine(this);

    button0.addActionListener(calcEngine);
    button1.addActionListener(calcEngine);
    button2.addActionListener(calcEngine);
    button3.addActionListener(calcEngine);
    button4.addActionListener(calcEngine);
    button5.addActionListener(calcEngine);
    button6.addActionListener(calcEngine);
    button7.addActionListener(calcEngine);
    button8.addActionListener(calcEngine);
    button9.addActionListener(calcEngine);
    buttonPoint.addActionListener(calcEngine);
    buttonPlus.addActionListener(calcEngine);
    buttonMinus.addActionListener(calcEngine);
    buttonDivide.addActionListener(calcEngine);
    buttonMultiply.addActionListener(calcEngine);
    buttonEqual.addActionListener(calcEngine);
    buttonSquareRt.addActionListener(calcEngine);
    buttonPercentage.addActionListener(calcEngine);
    buttonPlusMinus.addActionListener(calcEngine);
    buttonClear.addActionListener(calcEngine);

}

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

这是代码有问题的引擎 包装计算器

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JButton;

public class CalculatorEngine implements ActionListener {

Calculator parent; // a reference to Calculator window
char selectedAction = ' '; // +, -, /, or *

double currentResult = 0;

// Constructor stores the reference to the Calculator
// window in the member variable parent
CalculatorEngine(Calculator parent) {
    this.parent = parent;
}

public void actionPerformed(ActionEvent e) {

    // Get the source of this action
    JButton clickedButton = (JButton) e.getSource();
    String dispFieldText = parent.displayField.getText();
    double displayValue = 0;
    // Get the number from the text field
    // if it’s not empty
    if (!"".equals(dispFieldText)) {
        displayValue = Double.parseDouble(dispFieldText);
    }
    Object src = e.getSource();
    // For each action button memorize selected
    // action +, -, /, or *, store the current value
    // in the currentResult, and clean up the display
    // field for entering the next number

    if (src == parent.buttonPlus) {
        selectedAction = '+';
        currentResult = displayValue;
        parent.displayField.setText("");
    } else if (src == parent.buttonMinus) {
        selectedAction = '-';
        currentResult = displayValue;
        parent.displayField.setText("");
    } else if (src == parent.buttonDivide) {
        selectedAction = '/';
        currentResult = displayValue;
        parent.displayField.setText("");
    } else if (src == parent.buttonMultiply) {
        selectedAction = '*';
        currentResult = displayValue;
        parent.displayField.setText("");
    } else if (src == parent.buttonSquareRt) {
        selectedAction = 's';
        currentResult = displayValue;
        parent.displayField.setText("");
    } else if (src == parent.buttonPercentage){
        selectedAction = 'p';
        currentResult = displayValue;
        parent.displayField.setText("");
    } else if (src == parent.buttonPlusMinus){
        selectedAction = 'm';
        currentResult = displayValue;
        parent.displayField.setText("");
    }

    else if (src == parent.buttonEqual) {
        // Perform the calculations based on selectedAction
        // update the value of the variable currentResult
        // and display the result
        if (selectedAction == '+') {
            currentResult += displayValue;
            // Convert the result to String by concatenating
            // to an empty string and display it
            parent.displayField.setText("" + currentResult);
        } else if (selectedAction == '-') {
            currentResult -= displayValue;
            parent.displayField.setText("" + currentResult);
        } else if (selectedAction == '/') {
            currentResult /= displayValue;
            parent.displayField.setText("" + currentResult);
        } else if (selectedAction == '*') {
            currentResult *= displayValue;
            parent.displayField.setText("" + currentResult);
        } else if (selectedAction == 's') {
            currentResult = Math.sqrt(displayValue);
            parent.displayField.setText("" + currentResult);
        } else if (selectedAction == 'p') {
            currentResult = currentResult / 100;
            parent.displayField.setText("" + currentResult);
        } else if (selectedAction == 'm') {
            displayValue = currentResult * -1;
            parent.displayField.setText("" + currentResult);
        }

    } else {
        // For all numeric buttons append the button's
        // label to the text field
        String clickedButtonLabel = clickedButton.getText();
        parent.displayField.setText(dispFieldText + clickedButtonLabel);
    }
  }
}

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这段代码似乎可以像预期的那样工作，输入一个像64这样的数字，然后按下平方根按钮-这将清除displayField-然后按下equals按钮，它将显示结果

如果您希望更清楚地显示您应该按equals按钮来获得结果，您可能希望回显用户条目，该条目由表示要执行的功能的文本包围，例如：

else if (src == parent.buttonSquareRt) {
    selectedAction = 's';
    currentResult = displayValue;
    parent.displayField.setText("sqrt(" + currentResult + ")");
}

---

您可以从这里得到一些想法：根据您的代码，您必须先按sqrt按钮，然后按equals按钮，它才能实际计算和更新显示字段。根据你上面的问题，听起来你好像没有按“相等”按钮？如果你仔细看，你会发现所有的计算都是由“相等”按钮触发的。要改变这种行为，只需将所需的操作从equal button代码块移出，并移到上面相应的块中。一个建议：学会编写更少的代码。跳到阵列和循环课程。在更好地理解Java之前，不要使用UI代码。