Add new file

第一章代码01

+1.dialog.cpp
+1.dialog.cpp
+#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_pushButton_clicked()
+{
+    bool ok;
+    QString tempStr;
+    QString valueStr=ui->lineEdit->text();
+    int valueInt=valueStr.toInt(&ok);
+    double area=valueInt*valueInt*PI;
+    ui->label_2->setText(tempStr.setNum(area));
+}