Qt5开发及实例-CH101.rar，Qt5采用设计器Qt Designer实现计算圆面积的代码

#include "dialog.h" #include "ui_dialog.h" const static double PI=3.1416; Dialog::Dialog(QWidget *parent) : QDialog(parent), ui(new Ui::Dialog) { ui->setupUi(this); } Dialog::~Dialog() { delete ui; } void Dialog::on_countBtn_clicked() { bool ok; QString tempStr; QString valueStr=ui->radiusLineEdit->text(); int valueInt=valueStr.toInt(&ok); double area=valueInt*valueInt*PI;//计算圆面积 ui->areaLabel_2->setText(tempStr.setNum(area)); } void Dialog::on_radiusLineEdit_textChanged(const QString &arg1) { bool ok; QString tempStr; QString valueStr=ui->radiusLineEdit->text(); int valueInt=valueStr.toInt(&ok); double area=valueInt*valueInt*PI;//计算圆面积 ui->areaLabel_2->setText(tempStr.setNum(area)); }