请用Qt重新实现上面的程序

由于题目没有提供完整的程序代码，以下是一个使用Qt实现的简单的计算器程序：

mainwindow.h文件：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_num0Button_clicked();
    void on_num1Button_clicked();
    void on_num2Button_clicked();
    void on_num3Button_clicked();
    void on_num4Button_clicked();
    void on_num5Button_clicked();
    void on_num6Button_clicked();
    void on_num7Button_clicked();
    void on_num8Button_clicked();
    void on_num9Button_clicked();
    void on_plusButton_clicked();
    void on_minusButton_clicked();
    void on_multiplyButton_clicked();
    void on_divideButton_clicked();
    void on_clearButton_clicked();
    void on_equalsButton_clicked();

private:
    Ui::MainWindow *ui;
    QString currentNumber;
    QString operation;
    double result;
};

#endif // MAINWINDOW_H

mainwindow.cpp文件：

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

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    result = 0;
}

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

void MainWindow::on_num0Button_clicked()
{
    currentNumber.append("0");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num1Button_clicked()
{
    currentNumber.append("1");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num2Button_clicked()
{
    currentNumber.append("2");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num3Button_clicked()
{
    currentNumber.append("3");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num4Button_clicked()
{
    currentNumber.append("4");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num5Button_clicked()
{
    currentNumber.append("5");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num6Button_clicked()
{
    currentNumber.append("6");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num7Button_clicked()
{
    currentNumber.append("7");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num8Button_clicked()
{
    currentNumber.append("8");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_num9Button_clicked()
{
    currentNumber.append("9");
    ui->resultLabel->setText(currentNumber);
}

void MainWindow::on_plusButton_clicked()
{
    operation = "+";
    result += currentNumber.toDouble();
    currentNumber.clear();
}

void MainWindow::on_minusButton_clicked()
{
    operation = "-";
    result -= currentNumber.toDouble();
    currentNumber.clear();
}

void MainWindow::on_multiplyButton_clicked()
{
    operation = "*";
    result *= currentNumber.toDouble();
    currentNumber.clear();
}

void MainWindow::on_divideButton_clicked()
{
    operation = "/";
    result /= currentNumber.toDouble();
    currentNumber.clear();
}

void MainWindow::on_clearButton_clicked()
{
    currentNumber.clear();
    result = 0;
    operation.clear();
    ui->resultLabel->setText("0");
}

void MainWindow::on_equalsButton_clicked()
{
    if(operation == "+")
        result += currentNumber.toDouble();
    else if(operation == "-")
        result -= currentNumber.toDouble();
    else if(operation == "*")
        result *= currentNumber.toDouble();
    else if(operation == "/")
        result /= currentNumber.toDouble();

    currentNumber = QString::number(result);
    ui->resultLabel->setText(currentNumber);
}

其中，ui_mainwindow.h文件是Qt自动生成的，包含了UI界面的设计布局和各个控件的定义和信号槽连接。