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前言：由于之后接触到的东西要用到QT，装好QT之后决定先在上面写一个小程序——计算器。首先简单学习了一下QT基本操作，布局，信号槽。上网查找了一些QT的操作资料。能力不够，写出来了一个功能不全还花里胡哨的计算器（此处算是自我批评，认真的），看到后面你们就知道了。

一.创建工程：

打开Qt Creator,点击New Project创建工程，照着下面指示做就好了，比较简单。 填写名称和路径，然后下一步

可以自己修改类名

点击完成，然后点击完成，程序就创建好了。

二.界面设计

双击后缀为.ui的文件，进入设计界面

这是我设计的计算器界面，绿色部分是2个Label控件，用于显示。其他的都是QPushButton控件，可以点击，我修改了它们的名字，方便之后的操作。例如按钮0：名字改成button_0。当然不改也是可以的 到这里可以运行一下，可以看到还没有添加功能的界面 三.代码部分 右击项目，选择添加新文件，C++，C++Class。 然后类名就叫own。 这样可以方便区分代码的各个层面，也是我们应该养成的习惯。 own.h

#ifndef OWN_H    #define OWN_H    #include 
   
        #include 
    
                 class own    {    public:        own();            void set_num1(double num);     //获取这两个数        void set_num2(double num);        void set_sign(QString sign);       //获取操作符        QString result();                 //运算的结果        private:        double num1;     //定义两个浮点数        double num2;        QString sign;     //操作符    };        #endif // OWN_H
    
   

own.cpp

#include "own.h"own::own()               //构造函数{    this->num1=0;    this->num2=0;}void own::set_num1(double num){    this->num1=num;}void own::set_num2(double num){    this->num2=num;}void own::set_sign(QString sign){    this->sign=sign;}//双目运算符：加减乘除QString own::result(){    double result;    if(this->sign.length()>1)        return "ERROR";            //返回字符串，返回值是QString型    if(this->sign=="+")    {        result=num1+num2;    }    else if(this->sign=="-")    {        result=num1-num2;    }    else if(this->sign=="*")    {        result=num1*num2;    }    else if(this->sign=="÷")    {        if(this->num2==0)            return "ERROR";        result=num1/num2;    }    else    {        return QString::number(this->num1);    }    return QString::number(result);             //将结果转换成QString型}

calculator.h

#ifndef CALCULATOR_H#define CALCULATOR_H#include 
   
    #include 
    
     #include "own.h"/*#include 
     
      #include 
      
       */namespace Ui {class calculator;}class calculator : public QMainWindow{    Q_OBJECTpublic:    explicit calculator(QWidget *parent = 0);    ~calculator();private slots:    void on_btn_0_clicked();    void on_btn_1_clicked();    void on_btn_2_clicked();    void on_btn_3_clicked();    void on_btn_4_clicked();    void on_btn_5_clicked();    void on_btn_6_clicked();    void on_btn_7_clicked();    void on_btn_8_clicked();    void on_btn_9_clicked();    void on_btn_add_clicked();    void on_btn_sub_clicked();    void on_btn_mul_clicked();    void on_btn_div_clicked();    void on_btn_equal_clicked();    void on_btn_clear_clicked();    void on_btn_delete_clicked();    void on_btn_point_clicked();private:    Ui::calculator *ui;    QString tmp;      //获取Label_1    QString all;     //获取Label_2    own *own1;};#endif // CALCULATOR_H
      
     
    
   

calculator.cpp

#include "calculator.h"#include "ui_calculator.h"#include "own.h"calculator::calculator(QWidget *parent) :    QMainWindow(parent),    ui(new Ui::calculator){    own1=new own;    ui->setupUi(this);    //连接信号    connect(this->ui->button_0,SIGNAL(clicked(bool)),this,SLOT(on_btn_0_clicked()));    connect(this->ui->button_1,SIGNAL(clicked(bool)),this,SLOT(on_btn_1_clicked()));    connect(this->ui->button_2,SIGNAL(clicked(bool)),this,SLOT(on_btn_2_clicked()));    connect(this->ui->button_3,SIGNAL(clicked(bool)),this,SLOT(on_btn_3_clicked()));    connect(this->ui->button_4,SIGNAL(clicked(bool)),this,SLOT(on_btn_4_clicked()));    connect(this->ui->button_5,SIGNAL(clicked(bool)),this,SLOT(on_btn_5_clicked()));    connect(this->ui->button_6,SIGNAL(clicked(bool)),this,SLOT(on_btn_6_clicked()));    connect(this->ui->button_7,SIGNAL(clicked(bool)),this,SLOT(on_btn_7_clicked()));    connect(this->ui->button_8,SIGNAL(clicked(bool)),this,SLOT(on_btn_8_clicked()));    connect(this->ui->button_9,SIGNAL(clicked(bool)),this,SLOT(on_btn_9_clicked()));    connect(this->ui->button_add,SIGNAL(clicked(bool)),this,SLOT(on_btn_add_clicked()));    connect(this->ui->button_sub,SIGNAL(clicked(bool)),this,SLOT(on_btn_sub_clicked()));    connect(this->ui->button_mul,SIGNAL(clicked(bool)),this,SLOT(on_btn_mul_clicked()));    connect(this->ui->button_div,SIGNAL(clicked(bool)),this,SLOT(on_btn_div_clicked()));    connect(this->ui->button_equal,SIGNAL(clicked(bool)),this,SLOT(on_btn_equal_clicked()));    connect(this->ui->button_clear,SIGNAL(clicked(bool)),this,SLOT(on_btn_clear_clicked()));    connect(this->ui->button_point,SIGNAL(clicked(bool)),this,SLOT(on_btn_point_clicked()));    connect(this->ui->button_delete,SIGNAL(clicked(bool)),this,SLOT(on_btn_delete_clicked()));    tmp="";    all="";}calculator::~calculator(){    delete ui;}

calculator.cpp绑定所有槽函数

void calculator::on_btn_0_clicked()    {       tmp+=ui->button_0->text();       this->ui->label->setText(tmp);       all+="0";       this->ui->label_2->setText(all);    }        void calculator::on_btn_1_clicked()    {       tmp+=ui->button_1->text();       this->ui->label->setText(tmp);       all+="1";       this->ui->label_2->setText(all);    }        void calculator::on_btn_2_clicked()    {       tmp+=ui->button_2->text();       this->ui->label->setText(tmp);       all+="2";       this->ui->label_2->setText(all);    }        void calculator::on_btn_3_clicked()    {       tmp+=ui->button_3->text();       this->ui->label->setText(tmp);       all+="3";       this->ui->label_2->setText(all);    }        void calculator::on_btn_4_clicked()    {       tmp+=ui->button_4->text();       this->ui->label->setText(tmp);       all+="4";       this->ui->label_2->setText(all);    }        void calculator::on_btn_5_clicked()    {       tmp+=ui->button_5->text();       this->ui->label->setText(tmp);       all+="5";       this->ui->label_2->setText(all);    }        void calculator::on_btn_6_clicked()    {       tmp+=ui->button_6->text();       this->ui->label->setText(tmp);       all+="6";       this->ui->label_2->setText(all);    }        void calculator::on_btn_7_clicked()    {       tmp+=ui->button_7->text();       this->ui->label->setText(tmp);       all+="7";       this->ui->label_2->setText(all);    }        void calculator::on_btn_8_clicked()    {       tmp+=ui->button_8->text();       this->ui->label->setText(tmp);       all+="8";       this->ui->label_2->setText(all);    }

接上：

void calculator::on_btn_9_clicked()        {           tmp+=ui->button_9->text();           this->ui->label->setText(tmp);           all+="9";           this->ui->label_2->setText(all);        }                void calculator::on_btn_point_clicked()        {             tmp+=ui->button_point->text();             this->ui->label->setText(tmp);             all+=".";             this->ui->label_2->setText(all);        }                void calculator::on_btn_add_clicked()        {            float num=tmp.toFloat();            own1->set_num1(num);            tmp="";            QString ex=ui->button_add->text();            own1->set_sign(ex);            all+="+";            this->ui->label_2->setText(all);        }                void calculator::on_btn_sub_clicked()        {            float num=tmp.toFloat();            own1->set_num1(num);            tmp="";            QString ex=ui->button_sub->text();            own1->set_sign(ex);            all+="-";            this->ui->label_2->setText(all);        }                void calculator::on_btn_mul_clicked()        {            float num=tmp.toFloat();            own1->set_num1(num);            tmp="";            QString ex=ui->button_mul->text();            own1->set_sign(ex);            all+="*";            this->ui->label_2->setText(all);        }                void calculator::on_btn_div_clicked()        {            float num=tmp.toFloat();            own1->set_num1(num);            tmp="";            QString ex=ui->button_div->text();            own1->set_sign(ex);            all+="÷";            this->ui->label_2->setText(all);        }                void calculator::on_btn_equal_clicked()        {            float num=tmp.toFloat();            own1->set_num2(num);            QString res=own1->result();            ui->label->setText(res);            tmp=res;          //将计算结果赋值给tmp，可以用结果继续计算            all+="=";            this->ui->label_2->setText(all);        }

接上：

void calculator::on_btn_clear_clicked()    //清空置零    {       tmp="";       ui->label->setText("0");       all="";       this->ui->label_2->setText(all);    }        void calculator::on_btn_delete_clicked()     //删除前一个字符    {        tmp=tmp.left(tmp.length()-1);        this->ui->label->setText(tmp);        all=all.left(all.length()-1);        this->ui->label_2->setText(all);    }

main.cpp

#include "calculator.h"#include 
   
    int main(int argc, char *argv[]){    QApplication a(argc, argv);    calculator w;    w.show();    return a.exec();}
   

运行之后的界面

后序：由于第一次使用QT做项目，对QT还不是很熟悉，还有很多控件不了解，目前只做出来简单的计算器，还需要插入菜单、跳转事件等功能，还有这段代码最大的缺点是只是对字符串进行了操作，不能区别优先级和括号。后面如果要写功能更多的计算器，要运用到数据结构中的堆栈。下去学习一下之后会再写一个功能完整些的计算器。

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