用qt设计计算器，每行代码加注释

以下是用Qt设计计算器的代码，每行都附有注释解释代码的作用：

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

    // 连接数字按钮的信号与槽
    connect(ui->pushButton_0, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_1, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_2, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_3, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_4, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_5, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_6, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_7, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_8, SIGNAL(clicked()), this, SLOT(digitClicked()));
    connect(ui->pushButton_9, SIGNAL(clicked()), this, SLOT(digitClicked()));

    // 连接运算符按钮的信号与槽
    connect(ui->pushButton_add, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->pushButton_sub, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->pushButton_mul, SIGNAL(clicked()), this, SLOT(operatorClicked()));
    connect(ui->pushButton_div, SIGNAL(clicked()), this, SLOT(operatorClicked()));

    // 连接等号和归零按钮的信号与槽
    connect(ui->pushButton_eq, SIGNAL(clicked()), this, SLOT(equalClicked()));
    connect(ui->pushButton_clr, SIGNAL(clicked()), this, SLOT(clearClicked()));

    // 初始化运算符和操作数
    operatorClicked();
}

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

void MainWindow::digitClicked()
{
    // 获取被点击的数字按钮对象
    QPushButton *digitButton = qobject_cast<QPushButton *>(sender());

    // 获取按钮上显示的数字
    int digitValue = digitButton->text().toInt();

    // 获取当前文本框中的数字
    int currentValue = ui->lineEdit->text().toInt();

    // 将按钮上的数字添加到当前文本框中的数字
    int newValue = currentValue * 10 + digitValue;

    // 更新文本框中的数字
    ui->lineEdit->setText(QString::number(newValue));
}

void MainWindow::operatorClicked()
{
    // 获取被点击的运算符按钮对象
    QPushButton *operatorButton = qobject_cast<QPushButton *>(sender());

    // 获取按钮上的运算符
    QString operatorValue = operatorButton->text();

    // 获取当前文本框中的数字
    int currentValue = ui->lineEdit->text().toInt();

    // 如果当前文本框中没有数字，则将操作数设为0
    if (m_firstOperand.isNull()) {
        m_firstOperand = currentValue;
    }

    // 记录运算符
    m_operator = operatorValue;

    // 清空文本框，等待输入第二个操作数
    ui->lineEdit->clear();
}

void MainWindow::equalClicked()
{
    // 获取当前文本框中的数字
    int currentValue = ui->lineEdit->text().toInt();

    // 如果当前文本框中没有数字，则将操作数设为0
    if (m_firstOperand.isNull()) {
        m_firstOperand = currentValue;
    }

    // 根据运算符计算结果
    if (m_operator == "+") {
        m_result = m_firstOperand + currentValue;
    } else if (m_operator == "-") {
        m_result = m_firstOperand - currentValue;
    } else if (m_operator == "*") {
        m_result = m_firstOperand * currentValue;
    } else if (m_operator == "/")