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
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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
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SingleApplication
This is a replacement of the QSingleApplication for Qt5，地址为 https://github.com/itay-grudev/SingleApplication
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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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int main(int argc, char *argv[]) {
RunGuard guard("9F0FFF1A-77A0-4EF0-87F4-5494CA8181C7");
if (!guard.tryToRun()) {
return 0;
}
QApplication a(argc, argv);
a.exec();
}
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RunGuard.h
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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)
};
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RunGuard.cpp
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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();
}
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http://www.qtdebug.com/qtbook-misc-single-application/
SingleApplication
https://github.com/itay-grudev/SingleApplication