运行之后 怎样可以取消LCD哪里的运算过程 点击第二个数的时候 不要前面的 第一个数

运行之后 怎样可以取消LCD哪里的运算过程 点击第二个数的时候 不要前面的 第一个数
运行之后 怎样可以取消LCD哪里的运算过程 点击第二个数的时候 不要前面的 第一个数

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

Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget)
{
ui->setupUi(this);
this->num1=0;
this->num2=0;
}

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

void Widget::setNum1(int num)
{
num1=num;
}
void Widget::setNum2(int num)
{
num2=num;
}

void Widget::on_btnc_clicked()
{
this->str1.clear();
this->ui->lcdNumber->display(0);
this->ui->label->clear();

}

void Widget::on_btn1_clicked()
{
QString str = "1";
str1.append(str);

   ui->lcdNumber->display(str1);
   ui->label->setText(str1);

}

void Widget::on_btn2_clicked()
{
QString str = "2";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget:: on_btn3_clicked()
{
QString str = "3";
str1.append(str);
ui->lcdNumber->display(str1);

ui->label->setText(str1);

}

void Widget::on_btn4_clicked()
{
QString str = "4";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btn5_clicked()
{
QString str = "5";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btn6_clicked()
{
QString str = "6";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btn7_clicked()
{
QString str = "7";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btn8_clicked()
{
QString str = "8";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btn9_clicked()
{
QString str = "9";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btn0_clicked()
{
QString str = "0";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btnp_clicked()
{
QString str = ".";
str1.append(str);
ui->lcdNumber->display(str1);
ui->label->setText(str1);
}

void Widget::on_btnadd_clicked()
{
oper = '+';
QString str = " + ";
str1.append(str);
ui->label->setText(str1);

}

void Widget::on_btnsub_clicked()
{
oper = '-';
QString str = " - ";
str1.append(str);
ui->label->setText(str1);
}

void Widget::on_btnplus_clicked()
{
oper = '*';
QString str = " * ";
str1.append(str);
ui->label->setText(str1);
}

void Widget::on_btndiv_clicked()
{

oper = '/';
QString str = " / ";
str1.append(str);

ui->label->setText(str1);
// oper = '/';
// ui->label->setText(flag);

// QString str = " / ";
// str1.append(str);
// ui->label->setText(str1);
// bool ok;
// int num =this->str1.toInt(&ok);
//this->setNum1(arry[0]);
// this->str1="";
//QString ex=ui->btndiv->setText(str);
// QString qoper=this->ui->btndiv->setText(flag);
// this->setNum1(arry[0]);
//this->setFlag(ex);

ui->label->setText(str1);

}

void Widget::on_btnback_clicked()
{

this->ui->label->clear();
str1=str1.left(str1.length()-1);

this->ui->lcdNumber->display(str1);
}

void Widget::on_btnequ_clicked()
{

QStringList Str_List  = str1.split(" ");
Str_List[0] = Str_List[0].simplified();
arry[0] = Str_List[0].toDouble();
this->setNum2(arry[2]);

// arry[0]=num1;

Str_List[2] = Str_List[2].simplified();
arry[2] = Str_List[2].toDouble();

// arry[2]=num2;

// bool ok;
// int num =this->str1.toInt(&ok);
// this->setNum2(num);
// QString res=this->doExpr();
// this->ui->lcdNumber->display(res);
// this->str1="";

switch(oper)
   {
       case '+':
           result = arry[0] + arry[2];
       break;

       case '-':
           result = arry[0] - arry[2];
       break;

       case '*':
           result = arry[0] * arry[2];
       break;

       case '/':
           if (0 != arry[2])
               result = arry[0] / arry[2];
           else
               result =0;
               qDebug()<<"error";
       break;

   default:
       break;
   }



 ui->lcdNumber->display(QString::number (result));

// ui->label->setText(QString::number (result));
}

void Widget::on_pushButton_2_clicked()
{
this->str1.clear();
this->ui->lcdNumber->display(0);
this->ui->label->clear();
}

// ui->lcdNumber->display(QString::number (result));
// ui->label->setText(QString::number (result));