QT实现简单计算器

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一、模块图

二、核心算法 —– 中缀表达式转化为后缀表达式

1、将中缀表达式转换为后缀表达式的算法思想：
1）计算机实现转换：
·开始扫描；
·数字时，加入后缀表达式；
·运算符：
a. 若为 ‘(‘，入栈；
b. 若为 ‘)’，则依次把栈中的的运算符加入后缀表达式中，直到出现’(‘，从栈中删除’(’ ；
c. 若为 除括号外的其他运算符， 当其优先级高于除’(‘以外的栈顶运算符时，直接入栈。否则从栈顶开始，依次弹出比当前处理的运算符优先级高和优先级相等的运算符，直到一个比它优先级低的或者遇到了一个左括号为止。
·当扫描的中缀表达式结束时，栈中的的所有运算符出栈；
2）人工实现转换
这里我给出一个中缀表达式：a+b*c-(d+e)
第一步：按照运算符的优先级对所有的运算单位加括号：式子变成了：((a+(b*c))-(d+e))
第二步：转换前缀与后缀表达式
前缀：把运算符号移动到对应的括号前面
则变成了：-( +(a *(bc)) +(de))
把括号去掉：-+a*bc+de 前缀式子出现
后缀：把运算符号移动到对应的括号后面
则变成了：((a(bc)* )+ (de)+ )-
把括号去掉：abc*+de+- 后缀式子出现
发现没有，前缀式，后缀式是不需要用括号来进行优先级的确定的。如表达式：3+(2-5)*6/3
后缀表达式 栈
3_________________+
3 ______+(
3 2 _____+(-
3 2 5 -___ +
3 2 5 - ___+*
3 2 5 - 6 * _+/
3 2 5 - 6 *3 ____+/
3 2 5 - 6 *3 /+__
(“_“用于隔开后缀表达式与栈)
另外一个人认为正确的转换方法:
遍历中缀表达式的每个节点，如果：
1、 该节点为操作数：
直接拷贝进入后缀表达式
2、 该节点是运算符，分以下几种情况：
A、 为“（”运算符：
压入临时堆栈中
B、 为“）”运算符：
不断地弹出临时堆栈顶部运算符直到顶部的运算符是“（”为止，从栈中删除’(‘。并把弹出的运算符都添加到后缀表达式中。
C、 为其他运算符，有以下步骤进行：
比较该运算符与临时栈栈顶指针的运算符的优先级，如果临时栈栈顶指针的优先级大于等于该运算符的优先级，弹出并添加到后缀表达式中，反复执行前面的比较工作，直到遇到一个栈顶指针的优先级低于该运算符的优先级，停止弹出添加并把该运算符压入栈中。
此时的比较过程如果出现栈顶的指针为‘（’，则停止循环并把该运算符压入栈中，注意：‘（’不要弹出来。
遍历完中缀表达式之后，检查临时栈，如果还有运算符，则全部弹出，并添加到后缀表达式中。
2）运用后缀表达式进行计算的具体做法：
建立一个栈S 。从左到右读表达式，如果读到操作数就将它压入栈S中，如果读到n元运算符(即需要参数个数为n的运算符)则取出由栈顶向下的n项按操作数运算，再将运算的结果代替原栈顶的n项，压入栈S中 。如果后缀表达式未读完，则重复上面过程，最后输出栈顶的数值则为结束。

**三、代码

**
mycalculator.h:

#ifndef MYCALCULATOR_H
#define MYCALCULATOR_H

#include <QWidget>
#include <QMainWindow>
#include <QPushButton>
#include <QLineEdit>
#include <QPalette>
#include <QStack>
#include <QPainter>
#include <QDateTime>

namespace Ui
{
class MyCalculator;
}

class MyCalculator : public QMainWindow
{
    Q_OBJECT
private:
    QLineEdit *lineEdit;//显示框
    QString input; //输入框

void MYcalculate();

private slots://定义槽函数
void buttonClicked();

public:
explicit MyCalculator(QWidget *parent = 0);
    ~MyCalculator();

// 增加 paintEvent() 的声明
protected:
void paintEvent(QPaintEvent *); //重写paintEvent()

private:
    Ui::MyCalculator *ui;
};

#endif // MYCALCULATOR_H

main.cpp:

#include "mycalculator.h"
#include <QApplication>
#include <QDesktopWidget>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MyCalculator w;
    w.setFixedHeight(525);
    w.setFixedWidth(300);
    w.move(QApplication::desktop()->rect().center()-QPoint(200,250));
w.show();

return a.exec();
}

mycalculator.cpp:

#include "mycalculator.h"
#include "ui_mycalculator.h"

void Change(const char *S,char OPS[],int &len);
void EXchange(char B[], int len, double &result,bool &flag);


//构造函数
MyCalculator::MyCalculator(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MyCalculator)
{
// 通过样式表给窗口设置背景图
// "MyCalculator" 为类名
// "../test/test.jpg": 为图片路径，相对于可执行程序的相对路径
this->setStyleSheet("MyCalculator{background-image: url(../MyCalculator/background1.png);} ");

    ui->setupUi(this);
    connect(ui->Button_0,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号0与槽函数
    connect(ui->Button_1,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号1与槽函数
    connect(ui->Button_2,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号2与槽函数
    connect(ui->Button_3,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号3与槽函数
    connect(ui->Button_4,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号4与槽函数
    connect(ui->Button_5,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号5与槽函数
    connect(ui->Button_6,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号6与槽函数
    connect(ui->Button_7,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号7与槽函数
    connect(ui->Button_8,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号8与槽函数
    connect(ui->Button_9,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号9与槽函数
    connect(ui->Button_add,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号+与槽函数
    connect(ui->Button_sub,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号-与槽函数
    connect(ui->Button_mul,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号*与槽函数
    connect(ui->Button_div,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号/与槽函数
    connect(ui->Button_backward,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号1/X与槽函数
    connect(ui->Button_C,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号C与槽函数
    connect(ui->Button_CE,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号CE与槽函数
    connect(ui->Button_XY,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号X^Y与槽函数
    connect(ui->Button_equal,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号=与槽函数
    connect(ui->Button_right,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号)与槽函数
    connect(ui->Button_remain,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号%与槽函数
    connect(ui->Button_time,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号Time与槽函数
    connect(ui->Button_left,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号(与槽函数
    connect(ui->Button_point,SIGNAL(clicked()),this,SLOT(buttonClicked()));//信号.与槽函数

    QPalette palette;
    palette.setColor(QPalette::Text,Qt::red);//设置字体颜色
    ui->lineEdit->setFont(QFont("Timers",20,QFont::Bold));//设置字体大小
    ui->lineEdit->setPalette(palette);

    input = "0";
}

//析构函数
MyCalculator::~MyCalculator()
{
delete ui;
}

// 重写paintEvent()
void MyCalculator::paintEvent(QPaintEvent *)
{
    QStyleOption opt; // 需要头文件#include <QStyleOption>
    opt.init(this);
    QPainter p(this); // 需要头文件#include <QPainter>
    style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
}

void MyCalculator::buttonClicked()//按钮触动槽函数
{
    lineEdit = ui->lineEdit;

    input = lineEdit->text();//输入框
    QPushButton *tb = qobject_cast<QPushButton *>(sender());//把信号的发送者转换成pushbutton类型
    QString text = tb->text();//text:获取或设置文本框的文本内容。


if(text == QString("CE"))
    {
        text = input.left(input.length()-1); //减去一字符
        lineEdit->setText(text);
    }
else if(text == QString("C"))//清空所有
    {
        input="";
        lineEdit->setText(input);
    }
else if(text == QString("±"))
    {
if(input=="")
            text='-';
else
         {
             QString::iterator p=text.end();
             p--;
if('-'==*p)
                 text=text.left(text.length()-1);
else
                 text=text+'-';
         }
         lineEdit->setText(text);
      }
else if(text == QString("1/X"))
     {
if(input != "")
             lineEdit->setText("1/"+input);
else
         {
             lineEdit->setText("divisor can't be 0");
         }
     }
else if(text == QString("X^Y"))
    {
if(input != "")
            lineEdit->setText(input+"^");
    }
else if(text == QString("Time"))
     {
         text=QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm"); //格式化输出当前时间
         lineEdit->setText(text);
     }
else if(text == QString("="))
    {
std::string str=input.toStdString();//QString转化为String
const char *S=str.c_str();//整个输入框的字符串
char OPS[50];//中缀表达式
int len;//去掉括号之后中缀表达式的长度
double result;//计算结果
            QString change;
bool flag1 = true;//判断出书是否为0的标志
            Change(S,OPS,len);
            EXchange(OPS,len,result,flag1);
if(flag1 == false)
            {
                lineEdit->clear();
                lineEdit->setText("divisor can't be 0");
            }
else
            {
                change=QString::number(result,10,6);//将计算结果转换为字符串
                lineEdit->setText(change);
            }
    }
else//+ - * / % 0-9
     {
          lineEdit->setText(input+=text);
     }
   }


void Change(const char *S,char OPS[],int &len)//将中缀表达式转变为后缀表达式
{
    QStack<char> OPE;//符号栈
unsigned int i,j=0;
unsigned int tmp = strlen(S);
for (i = 0; i < tmp; i++)
    {
switch (S[i])
        {
case'+': 
if(OPE.isEmpty())//栈为空
             OPE.push(S[i]);
else if (OPE.top() == '*' || OPE.top() == '/' || OPE.top() == '%' || OPE.top()=='^')
            {
                OPS[j++] = OPE.pop();//弹出比'+'运算符优先级高和相等的运算符，依次加入后缀表达式
                i--;
            }
else
                OPE.push(S[i]);
break;
case'-':
if(i!=0 && '('!=S[i-1])//正数
            {
if(OPE.isEmpty())//栈为空
                  OPE.push(S[i]);
else if (OPE.top() == '*' || OPE.top() == '/'|| OPE.top() == '%' || OPE.top()=='^')//弹出比'-'运算符优先级高和相等的运算符，依次加入后缀表达式
             {
               OPS[j++] = OPE.pop();
               i--;
             }
else
                OPE.push(S[i]);
            }
else//负数
            {
while ((S[i] >= '0'&&S[i] <= '9' ) || S[i] == '.' || ('-'==S[i]&&(S[i-1]<'0'||S[i-1]>'9')))
                {
                    OPS[j++] = S[i];
if('-'==S[i])
                      OPS[j++]='@';
                    i++;
                }
                i--;
                OPS[j++] = '#';  //数字中的间隔符
            }
break;
case '^':
                OPE.push(S[i]);
break;
case'*':
if(OPE.isEmpty())//栈为空
               OPE.push(S[i]);
else if (OPE.top() == '^')
            {
                OPS[j++] = OPE.pop();//弹出比'/'运算符优先级高和相等的运算符，依次加入后缀表达式
                i--;
            }
else
                OPE.push(S[i]);
break;
case'/':
if(OPE.isEmpty())//栈为空
               OPE.push(S[i]);
else if (OPE.top() == '^')
            {
                OPS[j++] = OPE.pop();//弹出比'/'运算符优先级高和相等的运算符，依次加入后缀表达式
                i--;
            }
else
                OPE.push(S[i]);
break;
case '%':
if(OPE.isEmpty())//栈为空
               OPE.push(S[i]);
else if (OPE.top() == '^'|| OPE.top()=='*' || OPE.top()=='/')
            {
                OPS[j++] = OPE.pop();//弹出比'%'运算符优先级高和相等的运算符，依次加入后缀表达式
                i--;
            }
else
                OPE.push(S[i]);
break;
case'(':
            OPE.push(S[i]);
break;
case')':
while (OPE.top() != '(')//依次把栈中的运算符加入后缀表达式并将其出栈
            {
                OPS[j++] = OPE.pop();
            }
            OPE.pop();//从栈中弹出'('
break;
default:
while ((S[i] >= '0'&&S[i] <= '9') || S[i] == '.' || ('-'==S[i]&&S[i-1]<'0'&&S[i-1]>'9'))
            {

                OPS[j++] = S[i];

                i++;
            }
            i--;
            OPS[j++] = '#';  //数字中的间隔符
break;
        }
    }
while (!OPE.isEmpty())
    {
        OPS[j++] = OPE.pop();
    }
    len = j;
}

void EXchange(char B[], int len, double &result,bool &flag)//用后缀表达式计算结果
{
int i;
double a;
double b;
double c;
    QStack<double>SZ;
for (i = 0; i < len; i++)
    {
switch (B[i])
        {
case'^':
          {
            a = SZ.pop();
            b = SZ.pop();
            c = pow(b,a);
            SZ.push(c);
          }
break;
case'+':
           {
            a = SZ.pop();
            b = SZ.pop();
            c = b + a;
            SZ.push(c);
            }
break;
case'-':
           {
if('@'!=B[i+1])
            {
            a = SZ.pop();
            b = SZ.pop();
            c = b - a;
            SZ.push(c);
            }
else
            {
int jx = 0;
double dx;
char *stx = new char[10];
while (B[i] != '#')
                {
if('@'!=B[i])
                    stx[jx++] = B[i];
                    i++;

                }
                dx = atof(stx);//把字符串转换成浮点数
                SZ.push(dx);
delete stx;
            }
           }
break;
case'*':
           {
            a = SZ.pop();
            b = SZ.pop();
            c = b*a;
            SZ.push(c);
           }
break;
case'/':
           {
              a = SZ.pop();
              b = SZ.pop();
if (a == 0)
              {
                  flag = false;
return;
              }
              c = b / a;
              SZ.push(c);
           }
break;
case'%':
          {
           a = SZ.pop();
           b = SZ.pop();
if (a == 0)
           {
               flag = false;
return;
           }
           c = (int)b % (int)a;
           SZ.push(c);
          }
break;
default:
int j = 0;
double d;
char *st = new char[10];
while (B[i] != '#')
               {
                   st[j++] = B[i];
                   i++;
               }
               d = atof(st);//把字符串转换成浮点数
               SZ.push(d);
delete st;
break;
        }
    }
    result=SZ.top();
}

界面文件：mycalculator.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MyCalculator</class>
<widget class="QMainWindow" name="MyCalculator">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>302</width>
<height>546</height>
</rect>
</property>
<property name="windowTitle">
<string>MyCalculator</string>
</property>
<property name="styleSheet">
<string notr="true">background-color: qconicalgradient(cx:0, cy:0, angle:135, stop:0 rgba(255, 255, 0, 69), stop:0.375 rgba(255, 255, 0, 69), stop:0.423533 rgba(251, 255, 0, 145), stop:0.45 rgba(247, 255, 0, 208), stop:0.477581 rgba(255, 244, 71, 130), stop:0.518717 rgba(255, 218, 71, 130), stop:0.55 rgba(255, 255, 0, 255), stop:0.57754 rgba(255, 203, 0, 130), stop:0.625 rgba(255, 255, 0, 69), stop:1 rgba(255, 255, 0, 69));</string>
</property>
<widget class="QWidget" name="centralWidget">
<widget class="QPushButton" name="Button_time">
<property name="geometry">
<rect>
<x>80</x>
<y>450</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>Time</string>
</property>
</widget>
<widget class="QPushButton" name="Button_6">
<property name="geometry">
<rect>
<x>130</x>
<y>370</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>6</string>
</property>
</widget>
<widget class="QPushButton" name="Button_0">
<property name="geometry">
<rect>
<x>30</x>
<y>450</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>0</string>
</property>
</widget>
<widget class="QPushButton" name="Button_7">
<property name="geometry">
<rect>
<x>30</x>
<y>330</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>7</string>
</property>
</widget>
<widget class="QPushButton" name="Button_point">
<property name="geometry">
<rect>
<x>130</x>
<y>450</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>.</string>
</property>
</widget>
<widget class="QPushButton" name="Button_C">
<property name="geometry">
<rect>
<x>180</x>
<y>290</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>C</string>
</property>
</widget>
<widget class="QPushButton" name="Button_1">
<property name="geometry">
<rect>
<x>30</x>
<y>410</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>1</string>
</property>
</widget>
<widget class="QPushButton" name="Button_8">
<property name="geometry">
<rect>
<x>80</x>
<y>330</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>8</string>
</property>
</widget>
<widget class="QPushButton" name="Button_5">
<property name="geometry">
<rect>
<x>80</x>
<y>370</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>5</string>
</property>
</widget>
<widget class="QPushButton" name="Button_remain">
<property name="geometry">
<rect>
<x>230</x>
<y>330</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>%</string>
</property>
</widget>
<widget class="QPushButton" name="Button_mul">
<property name="geometry">
<rect>
<x>180</x>
<y>370</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>*</string>
</property>
</widget>
<widget class="QPushButton" name="Button_4">
<property name="geometry">
<rect>
<x>30</x>
<y>370</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>4</string>
</property>
</widget>
<widget class="QPushButton" name="Button_XY">
<property name="geometry">
<rect>
<x>230</x>
<y>290</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="styleSheet">
<string notr="true"/>
</property>
<property name="text">
<string>X^Y</string>
</property>
</widget>
<widget class="QPushButton" name="Button_3">
<property name="geometry">
<rect>
<x>130</x>
<y>410</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>3</string>
</property>
</widget>
<widget class="QPushButton" name="Button_add">
<property name="geometry">
<rect>
<x>180</x>
<y>450</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>+</string>
</property>
</widget>
<widget class="QPushButton" name="Button_equal">
<property name="geometry">
<rect>
<x>230</x>
<y>410</y>
<width>41</width>
<height>61</height>
</rect>
</property>
<property name="text">
<string>=</string>
</property>
</widget>
<widget class="QPushButton" name="Button_backward">
<property name="geometry">
<rect>
<x>230</x>
<y>370</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>1/X</string>
</property>
</widget>
<widget class="QPushButton" name="Button_sub">
<property name="geometry">
<rect>
<x>180</x>
<y>410</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>-</string>
</property>
</widget>
<widget class="QPushButton" name="Button_div">
<property name="geometry">
<rect>
<x>180</x>
<y>330</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="styleSheet">
<string notr="true">border-color: qlineargradient(spread:pad, x1:0, y1:0, x2:1, y2:0, stop:0 rgba(255, 0, 0, 255), stop:0.166 rgba(255, 255, 0, 255), stop:0.333 rgba(0, 255, 0, 255), stop:0.5 rgba(0, 255, 255, 255), stop:0.666 rgba(0, 0, 255, 255), stop:0.833 rgba(255, 0, 255, 255), stop:1 rgba(255, 0, 0, 255));</string>
</property>
<property name="text">
<string>/</string>
</property>
</widget>
<widget class="QPushButton" name="Button_CE">
<property name="geometry">
<rect>
<x>130</x>
<y>290</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>CE</string>
</property>
</widget>
<widget class="QPushButton" name="Button_right">
<property name="geometry">
<rect>
<x>80</x>
<y>290</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>)</string>
</property>
</widget>
<widget class="QPushButton" name="Button_left">
<property name="geometry">
<rect>
<x>30</x>
<y>290</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>(</string>
</property>
</widget>
<widget class="QPushButton" name="Button_2">
<property name="geometry">
<rect>
<x>80</x>
<y>410</y>
<width>41</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>2</string>
</property>
</widget>
<widget class="QPushButton" name="Button_9">
<property name="geometry">
<rect>
<x>130</x>
<y>330</y>
<width>41</width>
<height>21</height>
</rect>
</property>
<property name="text">
<string>9</string>
</property>
</widget>
<widget class="QLineEdit" name="lineEdit">
<property name="geometry">
<rect>
<x>10</x>
<y>20</y>
<width>281</width>
<height>61</height>
</rect>
</property>
<property name="styleSheet">
<string notr="true"/>
</property>
</widget>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>302</width>
<height>23</height>
</rect>
</property>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>

运行结果：

运行结果检查：
1.除数为0

2.加法

3.减法

4。Time

5.综合测验