用QT写一个C++的计算器

好的，下面是一个简单的 C++ 计算器程序，使用 QT 框架：

首先，在 QT Creator 中创建一个新的 QT Widgets 应用程序项目。接下来，打开 mainwindow.cpp 文件并添加以下代码：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // 连接数字按钮的信号和槽
    connect(ui->button_0, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_1, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_2, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_3, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_4, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_5, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_6, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_7, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_8, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->button_9, SIGNAL(clicked()), this, SLOT(digitClicked()));

    // 连接运算符按钮的信号和槽
    connect(ui->button_add, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->button_sub, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->button_mul, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->button_div, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->button_equal, SIGNAL(clicked()), this, SLOT(equalClicked()));

    // 初始化计算器状态
    m_state = STATE_FIRST_OPERAND;
    m_operator = OPERATOR_NONE;
    m_firstOperand = 0;
    m_secondOperand = 0;
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::digitClicked()
{
    QPushButton *button = (QPushButton *)sender();
    int digitValue = button->text().toInt();

    if (m_state == STATE_FIRST_OPERAND) {
        m_firstOperand = m_firstOperand * 10 + digitValue;
        ui->display->setText(QString::number(m_firstOperand));
    } else {
        m_secondOperand = m_secondOperand * 10 + digitValue;
        ui->display->setText(QString::number(m_secondOperand));
    }
}

void MainWindow::operatorClicked()
{
    QPushButton *button = (QPushButton *)sender();

    if (m_state == STATE_FIRST_OPERAND) {
        m_operator = getOperator(button->text());
        m_state = STATE_SECOND_OPERAND;
    } else {
        calculate();
        m_operator = getOperator(button->text());
        m_state = STATE_SECOND_OPERAND;
    }
}

void MainWindow::equalClicked()
{
    calculate();
    m_state = STATE_FIRST_OPERAND;
    m_operator = OPERATOR_NONE;
}

void MainWindow::calculate()
{
    int result = 0;

    switch (m_operator) {
    case OPERATOR_ADD:
        result = m_firstOperand + m_secondOperand;
        break;
    case OPERATOR_SUB:
        result = m_firstOperand - m_secondOperand;
        break;
    case OPERATOR_MUL:
        result = m_firstOperand * m_secondOperand;
        break;
    case OPERATOR_DIV:
        result = m_firstOperand / m_secondOperand;
        break;
    default:
        break;
    }

    ui->display->setText(QString::number(result));

    m_firstOperand = result;
    m_secondOperand = 0;
}

MainWindow::Operator MainWindow::getOperator(const QString &text)
{
    if (text == "+") {
        return OPERATOR_ADD;
    } else if (text == "-") {
        return OPERATOR_SUB;
    } else if (text == "*") {
        return OPERATOR_MUL;
    } else if (text == "/") {
        return OPERATOR_DIV;
    } else {
        return OPERATOR_NONE;
    }
}

然后，在 mainwindow.h 文件中添加以下代码：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

    enum State {
        STATE_FIRST_OPERAND,
        STATE_SECOND_OPERAND
    };

    enum Operator {
        OPERATOR_ADD,
        OPERATOR_SUB,
        OPERATOR_MUL,
        OPERATOR_DIV,
        OPERATOR_NONE
    };

private slots:
    void digitClicked();
    void operatorClicked();
    void equalClicked();

private:
    void calculate();
    Operator getOperator(const QString &text);

    Ui::MainWindow *ui;

    State m_state;
    Operator m_operator;
    int m_firstOperand;
    int m_secondOperand;
};

#endif // MAINWINDOW_H

最后，在 UI 界面中添加数字按钮和运算符按钮，并将它们的信号连接到对应的槽函数。

现在，您可以编译并运行该程序，测试您的计算器是否正确工作。