用qt做一个计算器

下面是一个简单的用Qt实现的计算器示例，可以进行加、减、乘、除的计算：

#include <QApplication>
#include <QWidget>
#include <QGridLayout>
#include <QLineEdit>
#include <QPushButton>

class Calculator : public QWidget
{
public:
    Calculator(QWidget *parent = 0);

private slots:
    void buttonClicked();

private:
    QLineEdit *lineEdit;
    QPushButton *buttons[16];
    QGridLayout *gridLayout;
    QString str;
};

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

    gridLayout = new QGridLayout(this);
    gridLayout->addWidget(lineEdit, 0, 0, 1, 4);

    for (int i = 0; i < 10; ++i) {
        buttons[i] = new QPushButton(QString::number(i), this);
        gridLayout->addWidget(buttons[i], (i + 3) / 3, (i - 1) % 3, 1, 1);
        connect(buttons[i], SIGNAL(clicked()), this, SLOT(buttonClicked()));
    }

    buttons[10] = new QPushButton("+", this);
    gridLayout->addWidget(buttons[10], 1, 3, 1, 1);
    connect(buttons[10], SIGNAL(clicked()), this, SLOT(buttonClicked()));

    buttons[11] = new QPushButton("-", this);
    gridLayout->addWidget(buttons[11], 2, 3, 1, 1);
    connect(buttons[11], SIGNAL(clicked()), this, SLOT(buttonClicked()));

    buttons[12] = new QPushButton("*", this);
    gridLayout->addWidget(buttons[12], 3, 3, 1, 1);
    connect(buttons[12], SIGNAL(clicked()), this, SLOT(buttonClicked()));

    buttons[13] = new QPushButton("/", this);
    gridLayout->addWidget(buttons[13], 4, 3, 1, 1);
    connect(buttons[13], SIGNAL(clicked()), this, SLOT(buttonClicked()));

    buttons[14] = new QPushButton("C", this);
    gridLayout->addWidget(buttons[14], 4, 0, 1, 1);
    connect(buttons[14], SIGNAL(clicked()), lineEdit, SLOT(clear()));

    buttons[15] = new QPushButton("=", this);
    gridLayout->addWidget(buttons[15], 4, 2, 1, 1);
    connect(buttons[15], SIGNAL(clicked()), this, SLOT(buttonClicked()));

    setLayout(gridLayout);
}

void Calculator::buttonClicked()
{
    QPushButton *button = qobject_cast<QPushButton *>(sender());
    if (button) {
        QString text = button->text();
        if (text == "=") {
            QString result = QString::number(eval(str));
            lineEdit->setText(result);
            str = "";
        } else if (text == "C") {
            lineEdit->clear();
            str = "";
        } else {
            str += text;
            lineEdit->setText(str);
        }
    }
}

int eval(QString str)
{
    int n = str.length();
    int op = '+', num = 0, ans = 0;
    for (int i = 0; i < n; ++i) {
        if (str[i].isDigit()) {
            num = num * 10 + (str[i].toLatin1() - '0');
        }
        if (!str[i].isDigit() && !str[i].isSpace() || i == n - 1) {
            if (op == '+') {
                ans += num;
            } else if (op == '-') {
                ans -= num;
            } else if (op == '*') {
                ans *= num;
            } else if (op == '/') {
                ans /= num;
            }
            op = str[i].toLatin1();
            num = 0;
        }
    }
    return ans;
}

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

这个计算器界面由一个QLineEdit和16个QPushButton组成。QPushButton是数字和运算符按钮，QLineEdit用于显示输入和结果。在buttonClicked()槽函数中，根据点击的按钮类型进行相应的处理。eval()函数用于实现表达式求值。