easycalculator.cpp

简单计算器,基于Qt平台实现,有基本的数学运算功能.

#include <QApplication>
#include <QLineEdit>
#include <QComboBox>
#include <QStringList>
#include <QLabel>
#include <QPushButton>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QDoubleValidator>

#include "easycalculator.h"

EasyCalculator::EasyCalculator(QWidget *parent) : QDialog(parent)
{
	QDoubleValidator *validator = new QDoubleValidator(this); 
	firstNumberEdit = new QLineEdit(tr("0"), this);
	firstNumberEdit->setValidator(validator);
	connect(firstNumberEdit, SIGNAL(textChanged(const QString &)), this, SLOT(calculate()));
	secondNumberEdit = new QLineEdit(tr("0"), this);
	secondNumberEdit->setValidator(validator);
	connect(secondNumberEdit, SIGNAL(textChanged(const QString &)), this, SLOT(calculate()));
	resultEdit = new QLineEdit(tr("0"), this);
	resultEdit->setReadOnly(true);
	
	QStringList signList;
	signList << tr("+") << tr("-") << tr("*") << tr("/");
	
	signCombo = new QComboBox(this);
	//signCombo->addItem(tr("+"));
	//signCombo->addItem(tr("-"));
	//signCombo->addItem(tr("*"));
	//signCombo->addItem(tr("/"));
	signCombo->addItems(signList);
	connect(signCombo, SIGNAL(currentIndexChanged(const QString &)), this, SLOT(calculate()));
	
	quitButton = new QPushButton(tr("Quit"), this);
	connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit()));
	
	QHBoxLayout *topLayout = new QHBoxLayout();
	topLayout->addWidget(firstNumberEdit);
	topLayout->addWidget(signCombo);
	topLayout->addWidget(secondNumberEdit);
	topLayout->addWidget(new QLabel(tr("=")));
	topLayout->addWidget(resultEdit);
	
	QVBoxLayout *layout = new QVBoxLayout();
	layout->addLayout(topLayout);
	layout->addWidget(quitButton);
	
	setLayout(layout);
}

void EasyCalculator::calculate()
{
	double first;
	double second;
	double result;
	QString firstString;
	QString secondString;
	QString resultString;
	
	firstString = firstNumberEdit->text();
	secondString = secondNumberEdit->text();
	
	first = firstString.toDouble();
	second = secondString.toDouble();
	
	switch (signCombo->currentIndex())
	{
		case 0:
			result = first + second;
			break;
		case 1:
			result = first - second;
			break;
		case 2:
			result = first * second;
			break;
		case 3:
			result = first / second;
			break;
		default:
			result = 0;
			break;
	}
	
	resultString.setNum(result, 'f', 3);
	
	resultEdit->setText(resultString);
}