QT实现四则运算计算器

#include "widget.h"
#include "ui_widget.h"


Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    this->setMaximumSize(240,300);
    this->setMinimumSize(240,300);

    this->setWindowTitle("计算器");

    QFont f("仿宋",14);
    ui->lineEdit->setFont(f);

    //按钮上放图片
//    QIcon icon=("D:\\");
//    ui->back->setIcon(icon);

    //改变按钮背景颜色
    ui->equal->setStyleSheet("background:green");

}

Widget::~Widget()
{
    delete ui;
}

void Widget::on_btn0_clicked()
{
    expression+="0";
    ui->lineEdit->setText(expression);
}

void Widget::on_btn1_clicked()
{
    expression+="1";
    ui->lineEdit->setText(expression);
}


void Widget::on_btn2_clicked()
{
    expression+="2";
    ui->lineEdit->setText(expression);
}

void Widget::on_btn3_clicked()
{
    expression+="3";
    ui->lineEdit->setText(expression);
}

void Widget::on_btn4_clicked()
{
    expression+="4";
    ui->lineEdit->setText(expression);
}

void Widget::on_btn5_clicked()
{
    expression+="5";
    ui->lineEdit->setText(expression);
}
void Widget::on_btn6_clicked()
{
    expression+="6";
    ui->lineEdit->setText(expression);
}
void Widget::on_btn7_clicked()
{
    expression+="7";
    ui->lineEdit->setText(expression);
}
void Widget::on_btn8_clicked()
{
    expression+="8";
    ui->lineEdit->setText(expression);
}
void Widget::on_btn9_clicked()
{
    expression+="9";
    ui->lineEdit->setText(expression);
}
void Widget::on_add_clicked()
{
    expression+="+";
    ui->lineEdit->setText(expression);
}

void Widget::on_sub_clicked()
{
    expression+="-";
    ui->lineEdit->setText(expression);
}


void Widget::on_mul_clicked()
{
    expression+="*";
    ui->lineEdit->setText(expression);
}


void Widget::on_div_clicked()
{
    expression+="/";
    ui->lineEdit->setText(expression);
}

void Widget::on_clear_clicked()
{
    expression.clear();
    ui->lineEdit->clear();
}

void Widget::on_back_clicked()
{
    expression.chop(1);
    ui->lineEdit->setText(expression);
}

void Widget::on_left_clicked()
{
    expression+="(";
    ui->lineEdit->setText(expression);
}

void Widget::on_right_clicked()
{
    expression+=")";
    ui->lineEdit->setText(expression);
}

void Widget::on_equal_clicked()
{
    QStack<int> s_num,s_opt;
    char opt[128]={0};
    int i=0,temp=0,num1,num2;

    QByteArray ba=expression.toLocal8Bit();     //QString 转换为QByteArray
    strcpy(opt,ba.data());                     //data可以把QByteArray转换为const char *


    //opt[i]还没进栈，看opt优先级与栈顶top的优先级情况，对栈进行操作，之后再操作opt
    while(opt[i]!='\0'||s_opt.empty()!=true)
    {
        if(opt[i]>='0'&&opt[i]<='9')                //操作数
        {
            temp=temp*10+opt[i]-'0';
            i++;
            if(opt[i]<'0'||opt[i]>'9')
            {
                s_num.push(temp);
                temp=0;
            }

        }
        else                                            //操作符
        {
            if(s_opt.empty()==true||                            //操作符入栈情况
                Priority(opt[i])>Priority(s_opt.top())||       //1、将要入栈的操作符比栈顶操作符优先级大
                (s_opt.top()=='('&&opt[i]!=')'))               //2、已经有（入栈，将要入栈的不是）而是其他（）的操作符
            {                                                   //3、操作符栈为空
                s_opt.push(opt[i]);
                i++;
                continue;
            }
            if(s_opt.top()=='('&&opt[i]==')')           //(!opt)
            {                                           //处理完（）内的运算符，剩余（），则直接出栈（
                s_opt.pop();
                i++;
                continue;
            }
            if(Priority(opt[i])<=Priority(s_opt.top())||        //操作符出栈，i无++
                (opt[i]==')'&&s_opt.top()!='(')||               //1、将要入栈的操作符比栈顶操作符优先级小，则先计算已在栈中的
                (opt[i]=='\0'&&s_opt.empty()!=true)             //2、将要入栈的操作符为），则计算（）内的运算符
                )                                               //3、没有要进行入栈的操作符了
            {
                char ch=s_opt.top();
                s_opt.pop();
                switch(ch)
                {
                     case '+':
                        num1=s_num.top();
                        s_num.pop();
                        num2=s_num.top();
                        s_num.pop();
                        s_num.push(num1+num2);
                        break;
                     case '-':
                        num1=s_num.top();
                        s_num.pop();
                        num2=s_num.top();
                        s_num.pop();
                        s_num.push(num1-num2);
                        break;
                     case '*':
                        num1=s_num.top();
                        s_num.pop();
                        num2=s_num.top();
                        s_num.pop();
                        s_num.push(num1*num2);
                        break;
                     case '/':
                        num1=s_num.top();
                        s_num.pop();
                        num2=s_num.top();
                        s_num.pop();
                        s_num.push(num1/num2);
                        break;
                }
            }
        }
    }
    ui->lineEdit->setText(QString::number(s_num.top()));
    expression.clear();

}

int Widget::Priority(char ch)
{
    switch(ch)
    {
        case '(':
            return 3;
        case '*':
        case '/':
            return 2;
        case '+':
        case '-':
            return 1;
        default:
            return 0;

    }
}

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