编写一段qt简易计算器的代码

以下是一个简单的 Qt 计算器的代码示例：

#include <QtWidgets>

class Calculator : public QWidget
{
    Q_OBJECT

public:
    Calculator(QWidget *parent = 0);

private slots:
    void digitClicked();
    void unaryOperatorClicked();
    void additiveOperatorClicked();
    void multiplicativeOperatorClicked();
    void equalClicked();
    void pointClicked();
    void changeSignClicked();
    void backspaceClicked();
    void clear();
    void clearAll();

private:
    void abortOperation();
    bool calculate(double rightOperand, const QString &pendingOperator);

    QDoubleSpinBox *display;

    QString pendingAdditiveOperator;
    QString pendingMultiplicativeOperator;
    QString pendingUnaryOperator;

    double factorSoFar;

    bool waitingForOperand;
    bool operandClicked;
};

Calculator::Calculator(QWidget *parent)
    : QWidget(parent), pendingAdditiveOperator(""), pendingMultiplicativeOperator(""), pendingUnaryOperator(""), factorSoFar(0.0), waitingForOperand(true), operandClicked(false)
{
    display = new QDoubleSpinBox();
    display->setRange(-999999999.0, 999999999.0);
    display->setDecimals(10);
    display->setSingleStep(0.1);
    display->setReadOnly(true);

    QPushButton *button0 = new QPushButton(tr("0"));
    QPushButton *button1 = new QPushButton(tr("1"));
    QPushButton *button2 = new QPushButton(tr("2"));
    QPushButton *button3 = new QPushButton(tr("3"));
    QPushButton *button4 = new QPushButton(tr("4"));
    QPushButton *button5 = new QPushButton(tr("5"));
    QPushButton *button6 = new QPushButton(tr("6"));
    QPushButton *button7 = new QPushButton(tr("7"));
    QPushButton *button8 = new QPushButton(tr("8"));
    QPushButton *button9 = new QPushButton(tr("9"));
    QPushButton *pointButton = new QPushButton(tr("."));
    QPushButton *changeSignButton = new QPushButton(tr("\302\261"));

    QPushButton *backspaceButton = new QPushButton(tr("Backspace"));
    QPushButton *clearButton = new QPushButton(tr("Clear"));
    QPushButton *clearAllButton = new QPushButton(tr("Clear All"));

    QPushButton *divisionButton = new QPushButton(tr("\303\267"));
    QPushButton *timesButton = new QPushButton(tr("\303\227"));
    QPushButton *minusButton = new QPushButton(tr("-"));
    QPushButton *plusButton = new QPushButton(tr("+"));
    QPushButton *equalButton = new QPushButton(tr("="));

    QGridLayout *mainLayout = new QGridLayout;
    mainLayout->setSizeConstraint(QLayout::SetFixedSize);

    mainLayout->addWidget(display, 0, 0, 1, 4);
    mainLayout->addWidget(button1, 1, 0);
    mainLayout->addWidget(button2, 1, 1);
    mainLayout->addWidget(button3, 1, 2);
    mainLayout->addWidget(divisionButton, 1, 3);
    mainLayout->addWidget(button4, 2, 0);
    mainLayout->addWidget(button5, 2, 1);
    mainLayout->addWidget(button6, 2, 2);
    mainLayout->addWidget(timesButton, 2, 3);
    mainLayout->addWidget(button7, 3, 0);
    mainLayout->addWidget(button8, 3, 1);
    mainLayout->addWidget(button9, 3, 2);
    mainLayout->addWidget(minusButton, 3, 3);
    mainLayout->addWidget(button0, 4, 0);
    mainLayout->addWidget(pointButton, 4, 1);
    mainLayout->addWidget(changeSignButton, 4, 2);
    mainLayout->addWidget(plusButton, 4, 3);
    mainLayout->addWidget(backspaceButton, 5, 0, 1, 2);
    mainLayout->addWidget(clearButton, 5, 2, 1, 1);
    mainLayout->addWidget(clearAllButton, 5, 3, 1, 1);
    mainLayout->addWidget(equalButton, 6, 3);

    setLayout(mainLayout);

    connect(button0, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button1, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button2, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button3, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button4, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button5, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button6, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button7, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button8, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(button9, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(pointButton, SIGNAL(clicked()), this, SLOT(pointClicked()));
    connect(changeSignButton, SIGNAL(clicked()), this, SLOT(changeSignClicked()));

    connect(backspaceButton, SIGNAL(clicked()), this, SLOT(backspaceClicked()));
    connect(clearButton, SIGNAL(clicked()), this, SLOT(clear()));
    connect(clearAllButton, SIGNAL(clicked()), this, SLOT(clearAll()));

    connect(divisionButton, SIGNAL(clicked()), this, SLOT(multiplicativeOperatorClicked()));
    connect(timesButton, SIGNAL(clicked()), this, SLOT(multiplicativeOperatorClicked()));
    connect(minusButton, SIGNAL(clicked()), this, SLOT(additiveOperatorClicked()));
    connect(plusButton, SIGNAL(clicked()), this, SLOT(additiveOperatorClicked()));
    connect(equalButton, SIGNAL(clicked()), this, SLOT(equalClicked()));
}

void Calculator::digitClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    int digitValue = clickedButton->text().toInt();
    if (display->value() == 0.0 && !waitingForOperand) {
        display->setValue(digitValue);
        waitingForOperand = true;
    } else {
        display->setValue(display->value() * 10 + digitValue);
    }
}

void Calculator::unaryOperatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();
    double operand = display->value();
    if (clickedOperator == tr("Sqrt")) {
        if (operand < 0.0) {
            abortOperation();
            return;
        }
        operand = std::sqrt(operand);
    }
    display->setValue(operand);
    waitingForOperand = true;
    operandClicked = true;
}

void Calculator::additiveOperatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();
    double operand = display->value();
    if (!pendingMultiplicativeOperator.isEmpty()) {
        if (!calculate(operand, pendingMultiplicativeOperator)) {
            abortOperation();
            return;
        }
        operand = factorSoFar;
        factorSoFar = 0.0;
        pendingMultiplicativeOperator = "";
    }
    if (!pendingAdditiveOperator.isEmpty()) {
        if (!calculate(operand, pendingAdditiveOperator)) {
            abortOperation();
            return;
        }
        display->setValue(factorSoFar);
    } else {
        factorSoFar = operand;
    }
    pendingAdditiveOperator = clickedOperator;
    waitingForOperand = true;
    operandClicked = true;
}

void Calculator::multiplicativeOperatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();
    double operand = display->value();
    if (!pendingMultiplicativeOperator.isEmpty()) {
        if (!calculate(operand, pendingMultiplicativeOperator)) {
            abortOperation();
            return;
        }
        operand = factorSoFar;
        factorSoFar = 0.0;
    }
    if (!pendingAdditiveOperator.isEmpty()) {
        if (!calculate(operand, pendingAdditiveOperator)) {
            abortOperation();
            return;
        }
        display->setValue(factorSoFar);
    } else {
        factorSoFar = operand;
    }
    pendingMultiplicativeOperator = clickedOperator;
    waitingForOperand = true;
    operandClicked = true;
}

bool Calculator::calculate(double rightOperand, const QString &pendingOperator)
{
    if (pendingOperator == tr("+")) {
        factorSoFar += rightOperand;
    } else if (pendingOperator == tr("-")) {
        factorSoFar -= rightOperand;
    } else if (pendingOperator == tr("\303\227")) {
        factorSoFar *= rightOperand;
    } else if (pendingOperator == tr("\303\267")) {
        if (rightOperand == 0.0) {
            return false;
        }
        factorSoFar /= rightOperand;
    }
    return true;
}

void Calculator::equalClicked()
{
    double operand = display->value();
    if (!pendingMultiplicativeOperator.isEmpty()) {
        if (!calculate(operand, pendingMultiplicativeOperator)) {
            abortOperation();
            return;
        }
        operand = factorSoFar;
        factorSoFar = 0.0;
        pendingMultiplicativeOperator = "";
    }
    if (!pendingAdditiveOperator.isEmpty()) {
        if (!calculate(operand, pendingAdditiveOperator)) {
            abortOperation();
            return;
        }
        pendingAdditiveOperator = "";
    } else {
        factorSoFar = operand;
    }
    display->setValue(factorSoFar);
    factorSoFar = 0.0;
    waitingForOperand = true;
    operandClicked = true;
}

void Calculator::pointClicked()
{
    if (!waitingForOperand) {
        display->setValue(display->value() + ".");
        waitingForOperand = true;
    }
}

void Calculator::changeSignClicked()
{
    display->setValue(display->value() * -1);
}

void Calculator::backspaceClicked()
{
    if (waitingForOperand) {
        return;
    }
    QString text = QString::number(display->value());
    text.chop(1);
    if (text.isEmpty() || text == "-") {
        text = "0";
    }
    display->setValue(text.toDouble());
}

void Calculator::clear()
{
    if (waitingForOperand) {
        return;
    }
    display->setValue(0.0);
    waitingForOperand = true;
}

void Calculator::clearAll()
{
    display->setValue(0.0);
    pendingAdditiveOperator = "";
    pendingMultiplicativeOperator = "";
    pendingUnaryOperator = "";
    factorSoFar = 0.0;
    waitingForOperand = true;
}

void Calculator::abortOperation()
{
    clearAll();
    display->setText(tr("####"));
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Calculator calc;
    calc.show();
    return app.exec();
}

这里使用了 QGridLayout 来布局界面，使用 QDoubleSpinBox 来显示计算结果。各个按钮的点击事件被连接到了相应的槽函数，实现了计算器的基本功能。