Qt给C程序做界面的简单应用(笔记)

Qt给C程序做界面的简单应用(笔记)

                                                                                                                             2009-12-20(NNF)

 

关键点:理解Qt只是一个图形库,给C做界面是把C函数嵌入到C++中去.

将要被调用的函数声明为extern,然后在Qt程序中使用

extern “C” int fun1();

extern “C” {int fun1();double fun2();};

的方式添加进去.

 

下面是一个实例:

 

/*To calculate your days from birthday to current time.*/

#include

#include

#include

 

static int is_LeapOrFract(const int year)              /*Leap year of Fractional year*/

{

       if((year%4==0&&year%100!=0)||year%400==0)

              return 366;

       else

              return 365;

}

 

static int is_Month_day(const int month,const int year)       /*How many days of this month*/

{

       if(month<1||month>12)

       {

              printf("Wrong number!\n");

              exit(-1);

       }

       if(month==1||month==3||month==5||month==7||month==8||month==10||month==12)

              return 31;

       else if(month==2)

       {

              if(is_LeapOrFract(year)==366)

                     return 29;

              else

                     return 28;

       }

       else

              return 30;

}

 

static int first_part(const int year,const int month,const int day)  /*The last days of birthyear*/

{

       int i,sum=0;

       for(i=12;i>month;i--)

       {

              sum+=is_Month_day(i,year);

       }

       return is_Month_day(month,year)-day+sum;

}

 

static int second_part(const int year,const int nyear)    /*The days of the years between birthyear and this year*/

{

       int i,sum=0;

       i=year+1;

       for(;i   

       {

              sum+=is_LeapOrFract(i);

       }

       return sum;

}

 

static int third_part(const int year,const int month,const int day) /*The past days of this year*/

{

       int i,sum=0;

       for(i=1;i

       {

              sum+=is_Month_day(i,year);

       }

       return sum+day;

}

 

extern int sumBirth(const int year,const int month,const int day)

{

              time_t now;

              struct tm *curtime;

              int nyear,nmonth,nday;

              int sum=0,sumfirst=0,sumsecond=0,sumthird=0;

 

              time(&now);                               /*Get the arguments of current time (year month and day)*/

              curtime=localtime(&now);

              nyear=curtime->tm_year+1900;

              nmonth=curtime->tm_mon+1;

              nday=curtime->tm_mday;

 

              sumfirst=first_part(year,month,day);   

 

              sumsecond=second_part(year,nyear);   

 

              sumthird=third_part(nyear,nmonth,nday);   

              if(year==nyear)

                     sum=sumthird-third_part(year,month,day);

              else

                     sum=sumfirst+sumsecond+sumthird;

 

       return sum;

}

上面为一个简单的C 语言程序,用来计算出生到当前日期的天数.要为这个程序做一个简单的界面.只是使用几个简单的Widget就可以实现.下面是Qt源码.分三个文件:ConversionScreen.h是头文件,里面声明了所需的类及函数和变量.ConversionScreen.cpp是程序的主体部分,包含了界面的实现和C函数的调用以及Signal与Slot的连接.main.cpp是程序的框架.将程序分开几部分写是个好习惯,会对以后的维护和代码重用很有帮助!

ConversionScreen.h

#ifndef CONVERSION_SCREEN_H

#define CONVERSION_SCREEN_H

 

#include

 

class QLabel;

class QHBoxLayout;

class QSpinBox;

 

class ConversionScreen:public QWidget

{

       Q_OBJECT

 

       public:

              ConversionScreen();         //构造函数,会在ConversionScreen.cpp里实现

              ~ConversionScreen(){};

 

       private slots:                   //自定义的槽实现.(想想规则)

              void setDays();

 

       private:

              void createScreen();           //用到的函数

              void createDays();

 

              QWidget *window;            //用到的Widget

              QSpinBox *spinYear;

              QSpinBox *spinMon;

              QSpinBox *spinDay;

              QLabel *labelYear;

              QLabel *labelMon;

              QLabel *labelDay;

              QLabel *labelDays;

              QSpinBox *textDay;

              QHBoxLayout *layout;

 

              int yearNum;           用到的变量

              int monNum;

              int dayNum;

              int daysNum;

};

#endif //CONVERSION_SCREEN_H

ConversionScreen.cpp

#include

#include

#include

#include

 

#include"ConversionScreen.h"

 

extern "C" {int sumBirth(const int year,const int mon,const int day);}; 将C函数包含进来

 

ConversionScreen::ConversionScreen():QWidget()  //构造函数的实现

{

       createScreen();              //调用自定义函数

}

 

void ConversionScreen::createScreen()  

{

 

       //window = new QWidget;

       this->setWindowTitle("Enter Your BirthDay");

       spinYear=new QSpinBox;

       spinMon=new QSpinBox;

       spinDay=new QSpinBox;

       spinYear->setRange(1900,2100);

       spinMon->setRange(1,12);

       spinDay->setRange(1,31);

       spinYear->setValue(1988);

 

       labelYear=new QLabel("year");

       labelMon=new QLabel("mon");

       labelDay=new QLabel("day");

       labelDays=new QLabel("Days");

       textDay=new QSpinBox;

       textDay->setRange(0,100000);

       layout=new QHBoxLayout;

                                        // 信号与槽的连接(想想为什么用this)

       QObject::connect(spinYear,SIGNAL(valueChanged(int)),this,SLOT(setDays()));

       QObject::connect(spinMon,SIGNAL(valueChanged(int)),this,SLOT(setDays()));

       QObject::connect(spinDay,SIGNAL(valueChanged(int)),this,SLOT(setDays()));

 

       layout->addWidget(spinYear);

       layout->addWidget(labelYear);

       layout->addWidget(spinMon);

       layout->addWidget(labelMon);

       layout->addWidget(spinDay);

       layout->addWidget(labelDay);

       layout->addWidget(textDay);

       layout->addWidget(labelDays);

       this->setLayout(layout);

       this->show();          //这个不能忘了

}

 

void ConversionScreen::createDays()

{

       yearNum=spinYear->value();

       monNum=spinMon->value();

       dayNum=spinDay->value();

       daysNum=sumBirth(yearNum,monNum,dayNum);   //C 函数的调用,其实很简单.

}

 

void ConversionScreen::setDays()                    //slot函数实现.(想想slot的规则)

{

       createDays();

       textDay->setValue(daysNum);

}

 

Main.cpp

#include

 

#include"ConversionScreen.h"   //包含自己写的头文件

 

int main(int argc,char **argv)     

{

       QApplication app(argc,argv);     //函数参数的传入

       ConversionScreen screen;        //创建对象

       screen.show();                 //显示

 

       return app.exec();               //返回等待处理

}

 

下图为程序在qvfb中的运行界面.

Bye