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 ​​​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#include <QApplication>#include <QSharedMemory>#include <QLocalServer>class SingleApplication : public QApplication{    Q_OBJECTpublic:    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.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;

// "single_application.h"#ifndef SINGLE_APPLICATION_H#define#include <QApplication>#include <QSharedMemory>class SingleApplication : public QApplication{    Q_OBJECTpublic:    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.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;}

// "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();}

亲测可用。

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