QT实现简单的计算器

效果图：

新建工程，创建类MainWindow，基类是QMainWindow，声明变量和函数、槽

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QPushButton>
#include <QLineEdit>

class MainWindow : public QMainWindow
{
    Q_OBJECT
protected:
    int num1,num2,result; //标记第一个数，第二个数和结果
    int operat; //运算符号
    int operat_flag;//标记是否输入符号
    QLineEdit *data;
    QPushButton *button_0;
    QPushButton *button_1;
    QPushButton *button_2;
    QPushButton *button_3;
    QPushButton *button_4;
    QPushButton *button_5;
    QPushButton *button_6;
    QPushButton *button_7;
    QPushButton *button_8;
    QPushButton *button_9;
    QPushButton *button_ce;
    QPushButton *button_jia;
    QPushButton *button_jian;
    QPushButton *button_cheng;
    QPushButton *button_chu;
    QPushButton *button_result;
    QString s;

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

public:
    void myLayout();
    void operation();
    void readNum(int num);
    void init_data();
private slots:
    void button_0_clicked();
    void button_1_clicked();
    void button_2_clicked();
    void button_3_clicked();
    void button_4_clicked();
    void button_5_clicked();
    void button_6_clicked();
    void button_7_clicked();
    void button_8_clicked();
    void button_9_clicked();
    void button_ce_clicked();
    void button_result_clicked();
    void button_cheng_clicked();
    void button_chu_clicked();
    void button_jia_clicked();
    void button_jian_clicked();
};


#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include <QPushButton>
#include <QLineEdit>
#include <QGridLayout>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
}

void MainWindow::myLayout(){
    QWidget *centerWindow = new QWidget;
    this->setCentralWidget(centerWindow);

    s = "";
    init_data();
    data = new QLineEdit("");

    button_0 = new QPushButton("0");
    button_1 = new QPushButton("1");
    button_2 = new QPushButton("2");
    button_3 = new QPushButton("3");
    button_4 = new QPushButton("4");
    button_5 = new QPushButton("5");
    button_6 = new QPushButton("6");
    button_7 = new QPushButton("7");
    button_8 = new QPushButton("8");
    button_9 = new QPushButton("9");
    button_ce = new QPushButton("CE");
    button_jia = new QPushButton("+");
    button_jian = new QPushButton("-");
    button_cheng = new QPushButton("*");
    button_chu = new QPushButton("/");
    button_result = new QPushButton("=");

    data->setFixedHeight(30);
    button_0->setMinimumHeight(50);
    button_1->setMinimumHeight(50);
    button_2->setMinimumHeight(50);
    button_3->setMinimumHeight(50);
    button_4->setMinimumHeight(50);
    button_5->setMinimumHeight(50);
    button_6->setMinimumHeight(50);
    button_7->setMinimumHeight(50);
    button_8->setMinimumHeight(50);
    button_9->setMinimumHeight(50);
    button_ce->setMinimumHeight(50);
    button_jia->setMinimumHeight(50);
    button_jian->setMinimumHeight(50);
    button_cheng->setMinimumHeight(50);
    button_chu->setMinimumHeight(50);
    button_result->setMinimumHeight(50);

    //连接信号
    connect(button_0,SIGNAL(clicked(bool)),this,SLOT(button_0_clicked()));
    connect(button_1,SIGNAL(clicked(bool)),this,SLOT(button_1_clicked()));
    connect(button_2,SIGNAL(clicked(bool)),this,SLOT(button_2_clicked()));
    connect(button_3,SIGNAL(clicked(bool)),this,SLOT(button_3_clicked()));
    connect(button_4,SIGNAL(clicked(bool)),this,SLOT(button_4_clicked()));
    connect(button_5,SIGNAL(clicked(bool)),this,SLOT(button_5_clicked()));
    connect(button_6,SIGNAL(clicked(bool)),this,SLOT(button_6_clicked()));
    connect(button_7,SIGNAL(clicked(bool)),this,SLOT(button_7_clicked()));
    connect(button_8,SIGNAL(clicked(bool)),this,SLOT(button_8_clicked()));
    connect(button_9,SIGNAL(clicked(bool)),this,SLOT(button_9_clicked()));
    connect(button_jia,SIGNAL(clicked(bool)),this,SLOT(button_jia_clicked()));
    connect(button_jian,SIGNAL(clicked(bool)),this,SLOT(button_jian_clicked()));
    connect(button_cheng,SIGNAL(clicked(bool)),this,SLOT(button_cheng_clicked()));
    connect(button_chu,SIGNAL(clicked(bool)),this,SLOT(button_chu_clicked()));
    connect(button_ce,SIGNAL(clicked(bool)),this,SLOT(button_ce_clicked()));
    connect(button_result,SIGNAL(clicked(bool)),this,SLOT(button_result_clicked()));

    QGridLayout * layout = new QGridLayout;

    layout->addWidget(data,1,1,1,4,Qt::Alignment());

    layout->addWidget(button_1,2,1,Qt::Alignment());
    layout->addWidget(button_2,2,2,Qt::Alignment());
    layout->addWidget(button_3,2,3,Qt::Alignment());
    layout->addWidget(button_jia,2,4,Qt::Alignment());

    layout->addWidget(button_4,3,1,Qt::Alignment());
    layout->addWidget(button_5,3,2,Qt::Alignment());
    layout->addWidget(button_6,3,3,Qt::Alignment());
    layout->addWidget(button_jian,3,4,Qt::Alignment());

    layout->addWidget(button_7,4,1,Qt::Alignment());
    layout->addWidget(button_8,4,2,Qt::Alignment());
    layout->addWidget(button_9,4,3,Qt::Alignment());
    layout->addWidget(button_cheng,4,4,Qt::Alignment());

    layout->addWidget(button_ce,5,1,Qt::Alignment());
    layout->addWidget(button_0,5,2,Qt::Alignment());
    layout->addWidget(button_result,5,3,Qt::Alignment());
    layout->addWidget(button_chu,5,4,Qt::Alignment());
    layout->setMargin(12);
    centerWindow->setLayout(layout);
}

MainWindow::~MainWindow()
{

}

void MainWindow::init_data()
{
    num1 = 0;
    num2 = 0;
    operat_flag = 0;
}

void MainWindow::readNum(int num)
{
      //如果是第一个操作数
      if(operat_flag == 0){
          num1 = num1 * 10 + num;
      }
      //如果是第二个操作数
      else{
          num2 = num2 * 10 + num;
      }
}

void MainWindow::operation()
{
    switch(operat){
    case 1:
        result = num1 + num2;
        break;
    case 2:
        result = num1 - num2;
        break;
    case 3:
        result = num1 * num2;
        break;
    case 4:
        result = num1 / num2;
        break;
    }
    //把结果存到num1中，清零num2
    num1 = result;
    num2 = 0;
    s = QString::number(result,10);
}

void MainWindow::button_0_clicked(){
    s += "0";
    data->setText(s);
    readNum(0);
}

void MainWindow::button_1_clicked(){
    s += "1";
    data->setText(s);
    readNum(1);
}

void MainWindow::button_2_clicked(){
    s += "2";
    data->setText(s);
    readNum(2);
}

void MainWindow::button_3_clicked(){
    s += "3";
    data->setText(s);
    readNum(3);
}

void MainWindow::button_4_clicked(){
    s += "4";
    data->setText(s);
    readNum(4);
}

void MainWindow::button_5_clicked(){
    s += "5";
    data->setText(s);
    readNum(5);
}

void MainWindow::button_6_clicked(){
    s += "6";
    data->setText(s);
    readNum(6);
}

void MainWindow::button_7_clicked(){
    s += "7";
    data->setText(s);
    readNum(7);
}

void MainWindow::button_8_clicked(){
    s += "8";
    data->setText(s);
    readNum(8);
}

void MainWindow::button_9_clicked(){
    s += "9";
    data->setText(s);
    readNum(9);
}

void MainWindow::button_ce_clicked(){
    s = "";
    data->setText("");
    //初始化数据
    init_data();
}

void MainWindow::button_jia_clicked(){
    s += "+";
    data->setText(s);
    operat_flag = 1;
    operat = 1;
}

void MainWindow::button_jian_clicked(){
    s += "-";
    data->setText(s);
    operat_flag = 1;
    operat = 2;
}

void MainWindow::button_cheng_clicked(){
    s += "*";
    data->setText(s);
    operat_flag = 1;
    operat = 3;
}

void MainWindow::button_chu_clicked(){
    s += "/";
    data->setText(s);
    operat_flag = 1;
    operat = 4;
}

void MainWindow::button_result_clicked(){
    operation();
    QString a = QString::number(result,10);
    data->setText(a);
}

main.cpp

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

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    w.setFixedSize(400,300);
    w.setWindowTitle("计算器");
    w.myLayout();
    return a.exec();
}

演示：

99*100=

结果

继续计算/99