一介绍

通过编写一个QSingleApplication类，来实现Qt程序的单例化，原文的作者是在Windows Vista + Qt4.4 下实现的，不过应用在其他平台上是没问题的。(本文是我在http://www.qtcentre.org/wiki/index.php?title=SingleApplication上看到的)

二代码

方案一：使用Qt中的QSharedMemory,QLocalServer和QLocalSocket实现(不过需要在你的.pro里加上QT += network)

别的没翻译，就是大概说了一下，直接来代码吧：

// "single_application.h"

#ifndef SINGLE_APPLICATION_H

#define SINGLE_APPLICATION_H

#include <QApplication>

#include <QSharedMemory>

#include <QLocalServer>

class SingleApplication : public QApplication

{

	Q_OBJECT

public:

	SingleApplication(int &argc, char *argv[], const QString uniqueKey);

	bool isRunning();

	bool sendMessage(const QString &message);

public slots:

	void receiveMessage();

signals:

	void messageAvailable(QString message);

private:

	bool _isRunning;

	QString _uniqueKey;

	QSharedMemory sharedMemory;

	QLocalServer *localServer;

	static const int timeout = 1000;

};

#endif // SINGLE_APPLICATION_H

// "single_application.cpp"

#include <QLocalSocket>

#include "single_application.h"

SingleApplication::SingleApplication(int &argc, char *argv[], const QString uniqueKey) : QApplication(argc, argv), _uniqueKey(uniqueKey)

{

	sharedMemory.setKey(_uniqueKey);

	if (sharedMemory.attach())

		_isRunning = true;

	else

	{

		_isRunning = false;

		// create shared memory.

		if (!sharedMemory.create(1))

		{

			qDebug("Unable to create single instance.");

			return;

		}

		// create local server and listen to incomming messages from other instances.

		localServer = new QLocalServer(this);

		connect(localServer, SIGNAL(newConnection()), this, SLOT(receiveMessage()));

		localServer->listen(_uniqueKey);

	}

}

// public slots.

void SingleApplication::receiveMessage()

{

	QLocalSocket *localSocket = localServer->nextPendingConnection();

	if (!localSocket->waitForReadyRead(timeout))

	{

		qDebug(localSocket->errorString().toLatin1());

		return;

	}

	QByteArray byteArray = localSocket->readAll();

	QString message = QString::fromUtf8(byteArray.constData());

	emit messageAvailable(message);

	localSocket->disconnectFromServer();

}

// public functions.

bool SingleApplication::isRunning()

{

	return _isRunning;

}

bool SingleApplication::sendMessage(const QString &message)

{

	if (!_isRunning)

		return false;

	QLocalSocket localSocket(this);

	localSocket.connectToServer(_uniqueKey, QIODevice::WriteOnly);

	if (!localSocket.waitForConnected(timeout))

	{

		qDebug(localSocket.errorString().toLatin1());

		return false;

	}

	localSocket.write(message.toUtf8());

	if (!localSocket.waitForBytesWritten(timeout))

	{

		qDebug(localSocket.errorString().toLatin1());

		return false;

	}

	localSocket.disconnectFromServer();

	return true;

方案二：使用Qt中的QSharedMemory,和QTimert实现,别的也没翻译，还是直接来代码吧：

// "single_application.h"

#ifndef SINGLE_APPLICATION_H

#define SINGLE_APPLICATION_H

#include <QApplication>

#include <QSharedMemory>

class SingleApplication : public QApplication

{

	Q_OBJECT

public:

	SingleApplication(int &argc, char *argv[], const QString uniqueKey);

	bool isRunning();

	bool sendMessage(const QString &message);

public slots:

	void checkForMessage();

signals:

	void messageAvailable(QString message);

private:

	bool _isRunning;

	QSharedMemory sharedMemory;

};

#endif // SINGLE_APPLICATION_H

// "single_application.cpp"

#include <QTimer>

#include <QByteArray>

#include "single_application.h"

SingleApplication::SingleApplication(int &argc, char *argv[], const QString uniqueKey) : QApplication(argc, argv)

{

	sharedMemory.setKey(uniqueKey);

	if (sharedMemory.attach())

		_isRunning = true;

	else

	{

		_isRunning = false;

		// attach data to shared memory.

		QByteArray byteArray("0"); // default value to note that no message is available.

		if (!sharedMemory.create(byteArray.size()))

		{

			qDebug("Unable to create single instance.");

			return;

		}

		sharedMemory.lock();

		char *to = (char*)sharedMemory.data();

		const char *from = byteArray.data();

		memcpy(to, from, qMin(sharedMemory.size(), byteArray.size()));

		sharedMemory.unlock();

                // start checking for messages of other instances.

		QTimer *timer = new QTimer(this);

		connect(timer, SIGNAL(timeout()), this, SLOT(checkForMessage()));

		timer->start(1000);

	}

}

// public slots.

void SingleApplication::checkForMessage()

{

	sharedMemory.lock();

	QByteArray byteArray = QByteArray((char*)sharedMemory.constData(), sharedMemory.size());

	sharedMemory.unlock();

	if (byteArray.left(1) == "0")

		return;

	byteArray.remove(0, 1);

	QString message = QString::fromUtf8(byteArray.constData());

	emit messageAvailable(message);

        // remove message from shared memory.

	byteArray = "0";

	sharedMemory.lock();

	char *to = (char*)sharedMemory.data();

	const char *from = byteArray.data();

	memcpy(to, from, qMin(sharedMemory.size(), byteArray.size()));

	sharedMemory.unlock();

}

// public functions.

bool SingleApplication::isRunning()

{

	return _isRunning;

}

bool SingleApplication::sendMessage(const QString &message)

{

	if (!_isRunning)

		return false;

	QByteArray byteArray("1");

	byteArray.append(message.toUtf8());

	byteArray.append('/0'); // < should be as char here, not a string!

	sharedMemory.lock();

	char *to = (char*)sharedMemory.data();

	const char *from = byteArray.data();

	memcpy(to, from, qMin(sharedMemory.size(), byteArray.size()));

	sharedMemory.unlock();

	return true;

}

三使用

// "main.cpp"

#include "single_application.h"

int main(int argc, char *argv[])

{

	SingleApplication app(argc, argv, "some unique key string");

	if (app.isRunning())

	{

		app.sendMessage("message from other instance.");

		return 0;

	}

	MainWindow *mainWindow = new MainWindow();

        // connect message queue to the main window.

	QObject::connect(&app, SIGNAL(messageAvailable(QString)), mainWindow, SLOT(receiveMessage(QString)));

        // show mainwindow.

	mainWindow->show();

	return app.exec();

}

我想代码都应该能看得懂吧，这个挺不错的~