Single Application

如果限制一个程序同时只能启动一个实例，有几个可以使用的库

• QtSingleApplication

  以前可以免费使用，后来只有商业版能里能用，在 Github 上也有一个 LGPL 协议的实现，地址为https://github.com/qtproject/qt-solutions/tree/master/qtsingleapplication

• SingleApplication

  This is a replacement of the QSingleApplication for Qt5，地址为 https://github.com/itay-grudev/SingleApplication

• RunGuard

  使用共享内存、简单、轻量化的实现，缺点是程序间不能通信，双击程序图标的时候不会激活已运行的实例显示到最前面，下面介绍 RunGuard 的使用

main.cpp

限制程序同时只能启动一个实例只需要在 main() 函数里调用 if (!guard.tryToRun()) { return 0; } 即可。

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#include "RunGuard.h"   int main(int argc, char *argv[]) { RunGuard guard("9F0FFF1A-77A0-4EF0-87F4-5494CA8181C7");   if (!guard.tryToRun()) { return 0; }   QApplication a(argc, argv); a.exec(); }

RunGuard.h

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#ifndef RUNGUARD_H #define RUNGUARD_H   #include <QObject> #include <QSharedMemory> #include <QSystemSemaphore>   class RunGuard { public: RunGuard(const QString& key); ~RunGuard();   bool isAnotherRunning(); bool tryToRun(); void release();   private: const QString key; const QString memLockKey; const QString sharedmemKey;   QSharedMemory sharedMem; QSystemSemaphore memLock;   Q_DISABLE_COPY(RunGuard) }; #endif // RUNGUARD_H

RunGuard.cpp

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#include "RunGuard.h" #include <QCryptographicHash>   namespace {   QString generateKeyHash(const QString& key, const QString& salt) { QByteArray data;   data.append(key.toUtf8()); data.append(salt.toUtf8()); data = QCryptographicHash::hash(data, QCryptographicHash::Sha1).toHex();   return data; }   }     RunGuard::RunGuard(const QString &key) : key(key) , memLockKey(generateKeyHash(key, "_memLockKey")) , sharedmemKey(generateKeyHash(key, "_sharedmemKey")) , sharedMem(sharedmemKey) , memLock(memLockKey, 1) { memLock.acquire(); { QSharedMemory fix(sharedmemKey); // Fix for *nix: http://habrahabr.ru/post/173281/ fix.attach(); } memLock.release(); }   RunGuard::~RunGuard() { release(); }   bool RunGuard::isAnotherRunning() { if (sharedMem.isAttached()) { return false; }   memLock.acquire(); const bool isRunning = sharedMem.attach(); if (isRunning) { sharedMem.detach(); } memLock.release();   return isRunning; }   bool RunGuard::tryToRun() { if (isAnotherRunning()) { // Extra check return false; }   memLock.acquire(); const bool result = sharedMem.create(sizeof(quint64)); memLock.release();   if (!result) { release(); return false; }   return true; }   void RunGuard::release() { memLock.acquire();   if (sharedMem.isAttached()) { sharedMem.detach(); }   memLock.release(); }

 

http://www.qtdebug.com/qtbook-misc-single-application/