Qt实现计算器

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 slots:
    int on_resultButton_clicked();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QMessageBox>
#include<QString>

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

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

int MainWindow::on_resultButton_clicked()
{
    double first=ui->firstInput->text().toDouble();
    double second=ui->secondInput->text().toDouble();
    double result;
    if(ui->comboBox->currentText()=="+")
    {
        result=first+second;
    }
    else if(ui->comboBox->currentText()=="-")
    {
        result=first-second;
    }
    else if(ui->comboBox->currentText()=="*")
    {
        result=first*second;
    }
    else if(ui->comboBox->currentText()=="/")
    {
        if(second==0)
        {
            QMessageBox::information(this,"Error","the second can not be 0");
            return 0;
        }
        else
        {
            result=first/second;
        }
    }
    QString string;
    ui->resultLabel->setText(string.setNum(result));
    return 0;
}

main.cpp

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

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

    return a.exec();
}