QT学习——四则运算

      四则运算即是对两个操作数进行加减乘除的操作，下面是利用QT写的简易的四则运算：

      mainwindow.h：

#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:
    Ui::MainWindow *ui;

private slots:
    void calSlot() ;  //实现计算的槽

};

#endif // MAINWINDOW_H

      main.cpp:

#include <QtGui/QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    
    return a.exec();
}

      mainwindow.cpp:

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

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QObject::connect(ui->calButton,SIGNAL(clicked()),this,SLOT(calSlot())) ;
}

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


void MainWindow::calSlot()
{
    int nfirst = ui->firstlineEdit->text().toInt() ;     //获取第一个编辑框的数值
    int nsecond = ui->secondlineEdit->text().toInt() ;   //获取第二个编辑框的数值
    int nresult ;

    if(ui->comboBox->currentIndex() == 0)    //+
    {
        nresult = nfirst + nsecond ;
    }

    if(ui->comboBox->currentIndex() == 1)    //-
    {
        nresult = nfirst - nsecond ;
    }

    if(ui->comboBox->currentIndex() == 2)    //*
    {
        nresult = nfirst * nsecond ;
    }

    if(ui->comboBox->currentIndex() == 3)    ///
    {
        if(nsecond == 0)
        {
            QMessageBox::information(this,"ERROR:","Second Number Can't Input 0 !");
             return ;
        }
        nresult = nfirst / nsecond ;
    }

    ui->resultlineEdit->setText(QString::number(nresult));    //将得到的结果显示在结果编辑框中
    QMessageBox::information(this,"Result:",QString::number(nresult));
}

程序运行结果：（加减乘除的选择在comboBox的下拉选项中）