Qt程序单次启动（QSingleApplication类）

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();}

亲测可用。
原文地址：https://blog.csdn.net/playstudy/article/details/7796691

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Qt程序单次启动（QSingleApplication类）

一介绍

二代码

三使用

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