简单计算器

界面：

头文件：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include<QMessageBox>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;
private slots:
    void calSlot();
};

#endif // MAINWINDOW_H

源文件：

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

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

    QObject::connect(ui->calButton,SIGNAL(clicked(bool)),this,SLOT(calSlot()));
}

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

void MainWindow::calSlot()
{
    int first=ui->firstLineEdit->text().toInt();
    int second=ui->secondLineEdit->text().toInt();
    int index=ui->comboBox->currentIndex();
    int result=0;
    switch(index)
    {
    case 0:
        result=first+second;
        break;
    case 1:
        result=first-second;
        break;
    case 2:
        result=first*second;
        break;
    case 3:
        if(second==0)
        {
            QMessageBox::warning(this,"警告","除数不能为0");
            ui->secondLineEdit->clear();
            ui->resultLineEdit->clear();
            return;
        }
        result=first/second;
        break;
    default:
        break;
    }

    ui->resultLineEdit->setText(QString::number(result));
    QMessageBox::information(this,"计算结果：",QString::number(result));
}