qt制作有键盘事件的计算器

以下是一个基于Qt的简单计算器，可以响应键盘事件：

#include <QtGui>

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();

protected:
    void keyPressEvent(QKeyEvent *event);

private:
    QPushButton *createButton(const QString &text, const char *member);
    void abortOperation();
    bool calculate(double rightOperand, const QString &pendingOperator);

    double sumSoFar;
    double factorSoFar;
    QString pendingAdditiveOperator;
    QString pendingMultiplicativeOperator;
    QString displayedValue;
    bool waitingForOperand;

    QLineEdit *display;
    QPushButton *backspaceButton;
    QPushButton *clearButton;
    QPushButton *clearAllButton;
    QPushButton *changeSignButton;
    QPushButton *pointButton;

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

    QPushButton *divisionButton;
    QPushButton *timesButton;
    QPushButton *minusButton;
    QPushButton *plusButton;
    QPushButton *equalButton;

    QGridLayout *mainLayout;
};

Calculator::Calculator(QWidget *parent)
    : QWidget(parent)
{
    sumSoFar = 0.0;
    factorSoFar = 0.0;
    pendingAdditiveOperator.clear();
    pendingMultiplicativeOperator.clear();
    displayedValue = "0";
    waitingForOperand = true;

    display = new QLineEdit("0");

    digitButtons[0] = createButton(tr("0"), SLOT(digitClicked()));
    digitButtons[1] = createButton(tr("1"), SLOT(digitClicked()));
    digitButtons[2] = createButton(tr("2"), SLOT(digitClicked()));
    digitButtons[3] = createButton(tr("3"), SLOT(digitClicked()));
    digitButtons[4] = createButton(tr("4"), SLOT(digitClicked()));
    digitButtons[5] = createButton(tr("5"), SLOT(digitClicked()));
    digitButtons[6] = createButton(tr("6"), SLOT(digitClicked()));
    digitButtons[7] = createButton(tr("7"), SLOT(digitClicked()));
    digitButtons[8] = createButton(tr("8"), SLOT(digitClicked()));
    digitButtons[9] = createButton(tr("9"), SLOT(digitClicked()));

    divisionButton = createButton(tr("/"), SLOT(multiplicativeOperatorClicked()));
    timesButton = createButton(tr("*"), SLOT(multiplicativeOperatorClicked()));
    minusButton = createButton(tr("-"), SLOT(additiveOperatorClicked()));
    plusButton = createButton(tr("+"), SLOT(additiveOperatorClicked()));
    equalButton = createButton(tr("="), SLOT(equalClicked()));

    pointButton = createButton(tr("."), SLOT(pointClicked()));
    changeSignButton = createButton(tr("\302\261"), SLOT(changeSignClicked()));
    backspaceButton = createButton(tr("Backspace"), SLOT(backspaceClicked()));
    clearButton = createButton(tr("Clear"), SLOT(clear()));
    clearAllButton = createButton(tr("Clear All"), SLOT(clearAll()));

    QGridLayout *mainLayout = new QGridLayout;
    mainLayout->setSizeConstraint(QLayout::SetFixedSize);
    mainLayout->addWidget(display, 0, 0, 1, 6);
    mainLayout->addWidget(backspaceButton, 1, 0, 1, 2);
    mainLayout->addWidget(clearButton, 1, 2, 1, 2);
    mainLayout->addWidget(clearAllButton, 1, 4, 1, 2);

    for (int i = 1; i < NumDigitButtons; ++i) {
        int row = ((9 - i) / 3) + 2;
        int column = ((i - 1) % 3) + 1;
        mainLayout->addWidget(digitButtons[i], row, column);
    }

    mainLayout->addWidget(digitButtons[0], 5, 1);
    mainLayout->addWidget(changeSignButton, 5, 2);
    mainLayout->addWidget(pointButton, 5, 3);
    mainLayout->addWidget(divisionButton, 2, 4);
    mainLayout->addWidget(timesButton, 3, 4);
    mainLayout->addWidget(minusButton, 4, 4);
    mainLayout->addWidget(plusButton, 5, 4);
    mainLayout->addWidget(equalButton, 5, 5);
    setLayout(mainLayout);

    setWindowTitle(tr("Calculator"));
}

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

void Calculator::digitClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    int digitValue = clickedButton->text().toInt();
    if (displayedValue == "0" && digitValue == 0.0)
        return;
    if (waitingForOperand) {
        displayedValue = QString::number(digitValue);
        waitingForOperand = false;
    } else {
        displayedValue = displayedValue + QString::number(digitValue);
    }
    display->setText(displayedValue);
}

void Calculator::unaryOperatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();
    double operand = displayedValue.toDouble();
    double result = 0.0;

    if (clickedOperator == tr("Sqrt")) {
        if (operand < 0.0) {
            abortOperation();
            return;
        }
        result = sqrt(operand);
    } else if (clickedOperator == tr("%")) {
        result = operand / 100.0;
    }

    displayedValue = QString::number(result);
    display->setText(displayedValue);
    waitingForOperand = true;
}

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

    if (!pendingMultiplicativeOperator.isEmpty()) {
        if (!calculate(operand, pendingMultiplicativeOperator)) {
            abortOperation();
            return;
        }
        operand = factorSoFar;
        factorSoFar = 0.0;
        pendingMultiplicativeOperator.clear();
        displayedValue = QString::number(operand);
        display->setText(displayedValue);
    }

    if (!pendingAdditiveOperator.isEmpty()) {
        if (!calculate(operand, pendingAdditiveOperator)) {
            abortOperation();
            return;
        }
        sumSoFar = displayedValue.toDouble();
    } else {
        sumSoFar = operand;
    }

    pendingAdditiveOperator = clickedOperator;
    waitingForOperand = true;
}

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

    if (!pendingMultiplicativeOperator.isEmpty()) {
        if (!calculate(operand, pendingMultiplicativeOperator)) {
            abortOperation();
            return;
        }
        operand = factorSoFar;
        factorSoFar = 0.0;
        pendingMultiplicativeOperator.clear();
        displayedValue = QString::number(operand);
        display->setText(displayedValue);
    }

    pendingMultiplicativeOperator = clickedOperator;
    if (pendingAdditiveOperator.isEmpty()) {
        factorSoFar = operand;
    } else {
        if (!calculate(operand, pendingAdditiveOperator)) {
            abortOperation();
            return;
        }
        sumSoFar = displayedValue.toDouble();
        factorSoFar = sumSoFar;
        sumSoFar = 0.0;
        pendingAdditiveOperator.clear();
    }
    waitingForOperand = true;
}

void Calculator::equalClicked()
{
    double operand = displayedValue.toDouble();

    if (!pendingMultiplicativeOperator.isEmpty()) {
        if (!calculate(operand, pendingMultiplicativeOperator)) {
            abortOperation();
            return;
        }
        operand = factorSoFar;
        factorSoFar = 0.0;
        pendingMultiplicativeOperator.clear();
    }

    if (!pendingAdditiveOperator.isEmpty()) {
        if (!calculate(operand, pendingAdditiveOperator)) {
            abortOperation();
            return;
        }
        pendingAdditiveOperator.clear();
    } else {
        sumSoFar = operand;
    }

    displayedValue = QString::number(sumSoFar);
    display->setText(displayedValue);
    sumSoFar = 0.0;
    waitingForOperand = true;
}

void Calculator::pointClicked()
{
    if (waitingForOperand)
        display->setText("0");
    if (!displayedValue.contains("."))
        displayedValue += ".";
    display->setText(displayedValue);
    waitingForOperand = false;
}

void Calculator::changeSignClicked()
{
    QString text = display->text();
    double value = text.toDouble();

    if (value > 0.0) {
        text.prepend(tr("-"));
    } else if (value < 0.0) {
        text.remove(0, 1);
    }

    display->setText(text);
}

void Calculator::backspaceClicked()
{
    if (waitingForOperand)
        return;

    QString text = display->text();
    text.chop(1);
    if (text.isEmpty()) {
        text = "0";
        waitingForOperand = true;
    }
    display->setText(text);
}

void Calculator::clear()
{
    if (waitingForOperand)
        return;

    display->setText("0");
    waitingForOperand = true;
}

void Calculator::clearAll()
{
    sumSoFar = 0.0;
    factorSoFar = 0.0;
    pendingAdditiveOperator.clear();
    pendingMultiplicativeOperator.clear();
    displayedValue = "0";
    waitingForOperand = true;
    display->setText(displayedValue);
}

void Calculator::keyPressEvent(QKeyEvent *event)
{
    switch (event->key()) {
    case Qt::Key_0:
        digitButtons[0]->animateClick();
        break;
    case Qt::Key_1:
        digitButtons[1]->animateClick();
        break;
    case Qt::Key_2:
        digitButtons[2]->animateClick();
        break;
    case Qt::Key_3:
        digitButtons[3]->animateClick();
        break;
    case Qt::Key_4:
        digitButtons[4]->animateClick();
        break;
    case Qt::Key_5:
        digitButtons[5]->animateClick();
        break;
    case Qt::Key_6:
        digitButtons[6]->animateClick();
        break;
    case Qt::Key_7:
        digitButtons[7]->animateClick();
        break;
    case Qt::Key_8:
        digitButtons[8]->animateClick();
        break;
    case Qt::Key_9:
        digitButtons[9]->animateClick();
        break;
    case Qt::Key_Plus:
        plusButton->animateClick();
        break;
    case Qt::Key_Minus:
        minusButton->animateClick();
        break;
    case Qt::Key_Asterisk:
        timesButton->animateClick();
        break;
    case Qt::Key_Slash:
        divisionButton->animateClick();
        break;
    case Qt::Key_Enter:
    case Qt::Key_Return:
        equalButton->animateClick();
        break;
    default:
        QWidget::keyPressEvent(event);
    }
}

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

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

在上面的代码中，我们重载了 `keyPressEvent` 函数，以便响应计算器界面中的键盘事件。同时，在构造函数中，我们将计算器界面的各个组件添加到了布局中，从而实现了计算器的界面。