QtGui实现计算圆的面积

dialog.h

#ifndef DIALOG_H

#define DIALOG_H

#include <QtWidgets/QDialog>

#include <QtWidgets/QLabel>

#include <QtWidgets//QLineEdit>

#include <QtWidgets/QPushButton>

#include <QtWidgets/QGridLayout>

const static double PI = 3.1416;

class Dialog : public QDialog

{

	Q_OBJECT//启动Qt元对象系统（比如支持SIGNAL/SLOT）

public:

	Dialog(QWidget *parent = 0);

	~Dialog();

private:

	QLabel *label1, *label2;

	QLineEdit *lineEdit;

	QPushButton *button;

private slots:

	void showArea();

};

#endif // DIALOG_H

dialog.cpp

#include "dialog.h"

Dialog::Dialog(QWidget *parent)

	: QDialog(parent)

{

	label1 = new QLabel(this);

	label1->setText(QStringLiteral("请输入圆的半径："));

	lineEdit = new QLineEdit(this);

	label2 = new QLabel(this);

	label2->setFrameStyle(QFrame::Panel | QFrame::Sunken);

	button = new QPushButton(this);

	button->setText(QStringLiteral("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()));

	//connect(lineEdit, SIGNAL(textChanged(QString)), 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));

}

Qt5已经删除了setCodecxx，同样滥用tr的副作用也消除了。

在遇到中文时，可以用

QStringLiteral

巴特西

QtGui实现计算圆的面积

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