Add new file

第一章代码02

+1.dialog.h
+1.dialog.h
+#ifndef DIALOG_H
+#define DIALOG_H
+
+#include <QDialog>
+#include <QLineEdit>
+#include <QPushButton>
+#include <QLabel>
+
+class Dialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    Dialog(QWidget *parent = 0);
+    ~Dialog();
+
+private:
+     QLabel *label1 ,*label2 ;
+     QLineEdit *lineEdit;
+     QPushButton *button;
+private slots:
+     void showArea();
+};
+#endif // DIALOG_H
+
+2.dialog.cpp
+#include "dialog.h"
+#include <QGridLayout>
+
+const static double PI =3.1416;
+
+Dialog::Dialog(QWidget *parent)
+    : QDialog(parent)
+{
+    label1=new QLabel(this);
+    label1->setText(tr("请输入圆的半径："));
+    lineEdit=new QLineEdit(this);
+    label2=new QLabel(this);
+    button=new QPushButton(this);
+    button->setText(tr("显示对应圆的面积： "));
+    QGridLayout *mainLayout= new QGridLayout(this);
+    mainLayout->addWidget(label1,0,0);
+    mainLayout->addWidget(lineEdit,0,1);
+    mainLayout->addWidget(label2,1,0);
+    mainLayout->addWidget(button,1,1);
+    connect(button,SIGNAL(clicked()),this,SLOT(showArea()));
+}
+
+Dialog::~Dialog()
+{
+}
+
+void Dialog::showArea()
+{
+    bool ok;
+    QString tempStr;
+    QString valueStr=lineEdit->text();
+    int valueInt=valueStr.toInt(&ok);
+    double area=valueInt*valueInt*PI;
+    label2->setText(tempStr.setNum(area));
+}