qt开发环境

没有加入弹出窗口

#ifndef MAINWINDOW_H#define MAINWINDOW_H#include <QMainWindow>namespace Ui {class MainWindow;}class MainWindow : public QMainWindow{    Q_OBJECTpublic:    explicit MainWindow(QWidget *parent = 0);    ~MainWindow();private slots:    void on_pushButton_clicked();private:    Ui::MainWindow *ui;};#endif // MAINWINDOW_H

#include "mainwindow.h"#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) :    QMainWindow(parent),    ui(new Ui::MainWindow){    ui->setupUi(this);    QObject::connect(ui->pushButton,SIGNAL(clicked()),this,SLOT(on_pushButton_clicked()));}MainWindow::~MainWindow(){    delete ui;}void MainWindow::on_pushButton_clicked(){    int first = ui->first->text().toInt();    int second = ui->second->text().toInt();    int result;    switch (ui->comboBox->currentIndex()) {    case 0:        result = first + second;        break;    case 1:        result = first - second;        break;    case 2:        result = first * second;        break;    case 3:        if(second < 0)            return;        result = first / second;        break;    default:        break;    }//    int first = ui->first->text().toInt();//    int second = ui->second->text().toInt();//    int sum = first + second;    ui->sum->setText(QString::number(result));}