qt实现计算器

要在Qt中实现一个计算器，可以按照以下步骤进行：

1. 创建一个Qt Widgets应用程序项目。
2. 在主窗口中添加一个QLineEdit（用于显示计算结果）和多个QPushButton（用于输入数字和运算符）。
3. 为每个QPushButton添加一个单击事件处理程序，以便在QLineEdit中显示相应的数字或运算符。
4. 创建一个QStack用于存储中间计算结果。
5. 在等号按钮的单击事件处理程序中，将QLineEdit中的表达式转换为逆波兰表达式，并计算结果。
6. 在计算过程中，使用QStack来存储中间结果，以便在计算完成后可以撤销操作。
7. 在AC按钮的单击事件处理程序中，清空QLineEdit和QStack，以便开始新的计算。

以下是一个简单的示例代码，演示了如何在Qt中实现一个计算器：

#include <QtWidgets>

class Calculator : public QWidget
{
    Q_OBJECT

public:
    Calculator(QWidget *parent = nullptr);

private slots:
    void digitClicked();
    void unaryOperatorClicked();
    void binaryOperatorClicked();
    void equalClicked();
    void clear();

private:
    QLineEdit *display;
    QStack<double> stack;

    enum { NumDigitButtons = 10 };
    QPushButton *digitButtons[NumDigitButtons];

    QPushButton *addButton;
    QPushButton *subButton;
    QPushButton *mulButton;
    QPushButton *divButton;
    QPushButton *equalButton;
    QPushButton *clearButton;

    double calculate(double operand1, double operand2, const QString &op);
};

Calculator::Calculator(QWidget *parent)
    : QWidget(parent)
{
    display = new QLineEdit;
    display->setReadOnly(true);
    display->setAlignment(Qt::AlignRight);
    display->setMaxLength(15);

    for (int i = 0; i < NumDigitButtons; ++i) {
        digitButtons[i] = createButton(QString::number(i), SLOT(digitClicked()));
    }

    addButton = createButton(tr("+"), SLOT(binaryOperatorClicked()));
    subButton = createButton(tr("-"), SLOT(binaryOperatorClicked()));
    mulButton = createButton(tr("*"), SLOT(binaryOperatorClicked()));
    divButton = createButton(tr("/"), SLOT(binaryOperatorClicked()));
    equalButton = createButton(tr("="), SLOT(equalClicked()));
    clearButton = createButton(tr("AC"), SLOT(clear()));

    QGridLayout *mainLayout = new QGridLayout;
    mainLayout->setSizeConstraint(QLayout::SetFixedSize);
    mainLayout->addWidget(display, 0, 0, 1, 4);
    mainLayout->addWidget(digitButtons[7], 1, 0);
    mainLayout->addWidget(digitButtons[8], 1, 1);
    mainLayout->addWidget(digitButtons[9], 1, 2);
    mainLayout->addWidget(addButton, 1, 3);
    mainLayout->addWidget(digitButtons[4], 2, 0);
    mainLayout->addWidget(digitButtons[5], 2, 1);
    mainLayout->addWidget(digitButtons[6], 2, 2);
    mainLayout->addWidget(subButton, 2, 3);
    mainLayout->addWidget(digitButtons[1], 3, 0);
    mainLayout->addWidget(digitButtons[2], 3, 1);
    mainLayout->addWidget(digitButtons[3], 3, 2);
    mainLayout->addWidget(mulButton, 3, 3);
    mainLayout->addWidget(digitButtons[0], 4, 0);
    mainLayout->addWidget(equalButton, 4, 1);
    mainLayout->addWidget(divButton, 4, 3);
    mainLayout->addWidget(clearButton, 4, 2);
    setLayout(mainLayout);
}

void Calculator::digitClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    int digitValue = clickedButton->text().toInt();
    display->setText(display->text() + QString::number(digitValue));
}

void Calculator::unaryOperatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();
    double operand = display->text().toDouble();

    if (clickedOperator == tr("sqrt")) {
        if (operand < 0.0) {
            QMessageBox::warning(this, tr("Calculator"),
                                 tr("Cannot compute the square root of a negative number."));
            return;
        }
        double result = std::sqrt(operand);
        display->setText(QString::number(result));
    }
}

void Calculator::binaryOperatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();
    double operand = display->text().toDouble();

    if (!stack.isEmpty()) {
        double result = calculate(stack.pop(), operand, clickedOperator);
        display->setText(QString::number(result));
        stack.push(result);
    } else {
        stack.push(operand);
    }

    lastOperator = clickedOperator;
}

void Calculator::equalClicked()
{
    double operand = display->text().toDouble();
    double result = calculate(stack.pop(), operand, lastOperator);
    display->setText(QString::number(result));
}

void Calculator::clear()
{
    display->setText("");
    stack.clear();
}

QPushButton *Calculator::createButton(const QString &text, const char *member)
{
    QPushButton *button = new QPushButton(text);
    connect(button, SIGNAL(clicked()), this, member);
    return button;
}

double Calculator::calculate(double operand1, double operand2, const QString &op)
{
    if (op == tr("+"))
        return operand1 + operand2;
    else if (op == tr("-"))
        return operand1 - operand2;
    else if (op == tr("*"))
        return operand1 * operand2;
    else if (op == tr("/"))
        return operand1 / operand2;
    return 0.0;
}

这个示例代码并不完整，但是可以帮助你了解Qt中如何实现一个简单的计算器。你可以根据需要进行修改和扩展。