小编在期末数据结构课设中遇到要做可视化界面的问题，特意去学习了一下Qt的用法，今天就来给大家分享一下。

我用的是Qt5.80，当然这只是一个简易的计算器Demo,，请大家勿喷。

首先我创建了一个Qt Widgets Application中的一个对话框项目，注意不用把UI文件勾选。

最终的UI界面是这样的：。

具体实现代码如下：

 calculator.pro

 #-------------------------------------------------

 #

 # Project created by QtCreator --05T14::

 #

 #-------------------------------------------------

 QT       += core gui

 greaterThan(QT_MAJOR_VERSION, ): QT += widgets

 TARGET = calculator

 TEMPLATE = app

 # The following define makes your compiler emit warnings if you use

 # any feature of Qt which as been marked as deprecated (the exact warnings

 # depend on your compiler). Please consult the documentation of the

 # deprecated API in order to know how to port your code away from it.

 DEFINES += QT_DEPRECATED_WARNINGS

 # You can also make your code fail to compile if you use deprecated APIs.

 # In order to do so, uncomment the following line.

 # You can also select to disable deprecated APIs only up to a certain version of Qt.

 #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.

 SOURCES += main.cpp\

         calculator.cpp

 HEADERS  += calculator.h
 calculator.cpp

 #ifndef CALCULATOR_H

 #define CALCULATOR_H

 #include <QDialog>

 #include <QPushButton>

 #include <QLineEdit>

 #include <QString>

 class Dialog : public QDialog

 {

     Q_OBJECT

 public:

     Dialog(QWidget *parent = );

     ~Dialog();

 protected:

     //声明需要的部件；

     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_plus;

     QPushButton* button_minus;

     QPushButton* button_multiply;

     QPushButton* button_devide;

     QPushButton* button_equal;

     QPushButton* button_clearAll;

     QLineEdit* lineEdit;

     QLineEdit* lineEdit_1;

     //声明需要的变量

     //第一个数，第二个数，运算结果；

     float num1,num2,result;

     QString S;//用于显示在lineEdit里面的字符串；

     //等号运算符的时候，判断是加、减、乘、除的哪一个

     char sign;

     int mark;//若点击过加减乘除，mark=2，默认为1；

     //声明处理按钮的槽函数

 private slots:

     //按照ui文件默认命名规则

     void on_button_0_clicked();

     void on_button_1_clicked();

     void on_button_2_clicked();

     void on_button_3_clicked();

     void on_button_4_clicked();

     void on_button_5_clicked();

     void on_button_6_clicked();

     void on_button_7_clicked();

     void on_button_8_clicked();

     void on_button_9_clicked();

     void on_button_plus_clicked();

     void on_button_minus_clicked();

     void on_button_multiply_clicked();

     void on_button_devide_clicked();

     void on_button_equal_clicked();

     void on_button_clearAll_clicked();

 };

 #endif // CALCULATOR_H
 calculator.cpp

 #include "calculator.h"

 #include <QGridLayout>

 Dialog::Dialog(QWidget *parent)

     : QDialog(parent)

 {

     //初始化变量

     num1=0.0;

     num2=0.0;

     result=0.0;

     S="";//显示在编辑框的字符串初始化为空

     mark=; //表示没有点击过加减乘除

     //初始化部件对象指针

     button_0=new QPushButton("");

     button_1=new QPushButton("");

     button_2=new QPushButton("");

     button_3=new QPushButton("");

     button_4=new QPushButton("");

     button_5=new QPushButton("");

     button_6=new QPushButton("");

     button_7=new QPushButton("");

     button_8=new QPushButton("");

     button_9=new QPushButton("");

     button_plus=new QPushButton("+");

     button_minus=new QPushButton("-");

     button_multiply=new QPushButton("*");

     button_devide=new QPushButton("/");

     button_equal=new QPushButton("=");

     button_clearAll=new QPushButton("c");

     lineEdit=new QLineEdit("请输入所要计算的值");

     lineEdit_1=new QLineEdit("ღCL");

     //使用网格布局，还有水平和垂直布局

     QGridLayout *Grid=new QGridLayout;

     Grid->addWidget(lineEdit,,,,,Qt::Alignment());

     //参数含义：widget部件指针；所在行；所在列；行宽；列宽；对齐方式；

     Grid->addWidget(lineEdit_1,,,,,Qt::Alignment());

     Grid->addWidget(button_0,,,Qt::Alignment());

     Grid->addWidget(button_1,,,Qt::Alignment());

     Grid->addWidget(button_2,,,Qt::Alignment());

     Grid->addWidget(button_3,,,Qt::Alignment());

     Grid->addWidget(button_4,,,Qt::Alignment());

     Grid->addWidget(button_5,,,Qt::Alignment());

     Grid->addWidget(button_6,,,Qt::Alignment());

     Grid->addWidget(button_7,,,Qt::Alignment());

     Grid->addWidget(button_8,,,Qt::Alignment());

     Grid->addWidget(button_9,,,Qt::Alignment());

     Grid->addWidget(button_plus,,,Qt::Alignment());

     Grid->addWidget(button_minus,,,Qt::Alignment());

     Grid->addWidget(button_multiply,,,Qt::Alignment());

     Grid->addWidget(button_devide,,,Qt::Alignment());

     Grid->addWidget(button_equal,,,Qt::Alignment());

     Grid->addWidget(button_clearAll,,,Qt::Alignment());

     //把Grid布局设置给当前创建的对话框对象

     this->setLayout(Grid);   //必不可少

     //实现连接函数  Connect函数参数 （pushbutton，signal，this指针，slot函数）

     connect(button_0,SIGNAL(clicked(bool)),this,SLOT(on_button_0_clicked()));

     connect(button_1,SIGNAL(clicked(bool)),this,SLOT(on_button_1_clicked()));

     connect(button_2,SIGNAL(clicked(bool)),this,SLOT(on_button_2_clicked()));

     connect(button_3,SIGNAL(clicked(bool)),this,SLOT(on_button_3_clicked()));

     connect(button_4,SIGNAL(clicked(bool)),this,SLOT(on_button_4_clicked()));

     connect(button_5,SIGNAL(clicked(bool)),this,SLOT(on_button_5_clicked()));

     connect(button_6,SIGNAL(clicked(bool)),this,SLOT(on_button_6_clicked()));

     connect(button_7,SIGNAL(clicked(bool)),this,SLOT(on_button_7_clicked()));

     connect(button_8,SIGNAL(clicked(bool)),this,SLOT(on_button_8_clicked()));

     connect(button_9,SIGNAL(clicked(bool)),this,SLOT(on_button_9_clicked()));

     connect(button_plus,SIGNAL(clicked(bool)),this,SLOT(on_button_plus_clicked()));

     connect(button_minus,SIGNAL(clicked(bool)),this,SLOT(on_button_minus_clicked()));

     connect(button_multiply,SIGNAL(clicked(bool)),this,SLOT(on_button_multiply_clicked()));

     connect(button_devide,SIGNAL(clicked(bool)),this,SLOT(on_button_devide_clicked()));

     connect(button_equal,SIGNAL(clicked(bool)),this,SLOT(on_button_equal_clicked()));

     connect(button_clearAll,SIGNAL(clicked(bool)),this,SLOT(on_button_clearAll_clicked()));

 }

 Dialog::~Dialog()

 {

 }

 //实现槽函数

 void Dialog::on_button_0_clicked()

 {

     S+="";

     lineEdit->setText(S);//把数据设置到编辑框

     if(mark==)

     {

         num1=num1*;//继续添0

     }

     else

     {

         num2=num2*;

     }

 }

 void Dialog::on_button_1_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_2_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_3_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_4_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_5_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_6_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_7_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_8_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_9_clicked()

 {

     S+="";

     lineEdit->setText(S);

     if(mark==)

     {

         num1=num1*+;

     }

     else

     {

         num2=num2*+;

     }

 }

 void Dialog::on_button_plus_clicked()

 {

     S+="+";

     sign='+';//设置标记为+

     mark=; //让其他按钮知道下一个点击的数累加到num2

     lineEdit->setText(S);

 }

 void Dialog::on_button_minus_clicked()

 {

     S+="-";

     sign='-';

     mark=;

     lineEdit->setText(S);

 }

 void Dialog::on_button_multiply_clicked()

 {

     S+="*";

     sign='*';

     mark=;

     lineEdit->setText(S);

 }

 void Dialog::on_button_devide_clicked()

 {

     S+="/";

     sign='/';

     mark=;

     lineEdit->setText(S);

 }

 void Dialog::on_button_equal_clicked()

 {

     S+="=";

     switch(sign)

     {

         case '+':

             result=num1+num2;

             break;

         case '-':

             result=num1-num2;

             break;

         case '*':

             result=num1*num2;

             break;

         case '/':

             result=num1/num2;

             break;

         default:

             break;

     }

     //S+=QString::number(result,10);//该函数result必须为int型

    // S+=QString("%1").arg(result);//float转QString  ,S+=保留之前的式子;

     //S+=result+'0';result大于等于10时报错

     S=QString("%1").arg(result);

     lineEdit_1->setText(S);

 }

 void Dialog::on_button_clearAll_clicked()

 {

     S="";

     //S+="";无法清除

     lineEdit->setText(S);

     lineEdit_1->setText(S);

     mark=;

     num1=0.0;

     num2=0.0;

     result=0.0;

 }
 calculator.cpp

 #include "calculator.h"

 #include <QApplication>

 int main(int argc, char *argv[])

 {

     QApplication a(argc, argv);

     Dialog w;

     w.show();

     return a.exec();

 }

本Demo中没有用到Qt designer，但是部件的声明和槽函数的声明都是按照designer的默认规则书写的。大体的思路是这样的：在构思好总体的UI布局后，在头文件中声明所需要的部件，不管是按钮、文本编辑框，还是行编辑框，都大同小异；之后在在cpp文件中实现相应的功能。该简易的计算器Demo只能满足两个运算数（原谅小编为小白），通过字符串的操作将0-9，+-*/显示在行编辑框内，最后在用户点击等号时，将float型的结果转化为QString输出。文中还使用了网格布局，在使用时千万不可忘记把布局格式设置给当前所创建的对话框对象（this->setLayout(Grid)）。

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