QT 中普通数值与字符串之间的转换

#pragma once

#include <QtWidgets/QMainWindow>
#include "ui_QtGuiApplication6.h"

class QtGuiApplication6 : public QMainWindow
{
  Q_OBJECT

public:
  QtGuiApplication6(QWidget *parent = Q_NULLPTR);

private:
  Ui::QtGuiApplication6Class ui;

private slots:
  void on_pushButton_clicked();
};

#include "QtGuiApplication6.h"
#include <qmessagebox.h>

QtGuiApplication6::QtGuiApplication6(QWidget *parent)
  : QMainWindow(parent)
{
  ui.setupUi(this);
  
}
void QtGuiApplication6::on_pushButton_clicked()
{
  int num = ui.lineEdit->text().toInt();
  float price = ui.lineEdit_2->text().toFloat();
  float total = num * price;//相乘计算    
  QString str;//    
  str=str.setNum(total,'f',2); //浮点数2位小数    
  str=str.sprintf("%.2f",total); //格式化输出浮点数    
  ui.lineEdit_3->setText(str);//在文本框里显示  editTotal为组件名  
}