[C++知识库]Qt实现程序单实例运行（QLocalServer）

效果：程序启动后会单实例运行，运行时点击exe不会出现新实例。

SingleApplication.h

#ifndef SINGLEAPPLICATION_H
#define SINGLEAPPLICATION_H

#include "temp.h"
#define TIMEOUT 500
#define SOFTWARE_NAME ("any name you want to set")

class SingleApplication : public QApplication
{
    Q_OBJECT
public:
    SingleApplication(int &argc, char **argv);

    bool IsRunning(); //当前是否有实例在运行

    QWidget *g_ptrWidget; //主窗口

private:
    QLocalServer *m_ptrServer; //本地服务器
    bool m_bIsRunning;

    void ConnectToServer(); //连接本地服务器

    void CreateLocalServer(); //创建服务器并监听

    void ActivateMainWindow(); //激活主窗口

private slots:
    void slotNewPendingConnection(); //收到新的连接
};

#endif // SINGLEAPPLICATION_H

SingleApplication.cpp

#include "SingleApplication.h"

SingleApplication::SingleApplication(int &argc, char **argv) : QApplication(argc, argv)
{
    m_bIsRunning = false;
    m_ptrServer = nullptr;

    ConnectToServer();
}

/**
 * @brief 当前是否有实例在运行
 */
bool SingleApplication::IsRunning()
{
    return m_bIsRunning;
}

/**
 * @brief 连接本地服务器
 */
void SingleApplication::ConnectToServer()
{
    QLocalSocket socket;
    socket.connectToServer(SOFTWARE_NAME);
    if(socket.waitForConnected(TIMEOUT)) //连接成功则程序已经在运行
    {
        qWarning()<<tr("%1已经处于运行中").arg(SOFTWARE_NAME);
        m_bIsRunning = true;
    }else //没有则创建
    {
        CreateLocalServer();
    }
}

/**
 * @brief 创建服务器并监听
 */
void SingleApplication::CreateLocalServer()
{
    m_ptrServer = new QLocalServer(this);
    connect(m_ptrServer, &QLocalServer::newConnection, this, &XCSingleApplication::slotNewPendingConnection);

    if(!m_ptrServer->listen(SOFTWARE_NAME)) //监听失败，清理残留进程
    {
        if(m_ptrServer->serverError() == QAbstractSocket::AddressInUseError)
        {
            if(QLocalServer::removeServer(SOFTWARE_NAME) == false)
            {
                qCritical()<<tr("清理%1残留进程失败，建议稍后或重启后再试").arg(SOFTWARE_NAME);
            }else
            {
                m_ptrServer->listen(SOFTWARE_NAME);
                return;
            }
        }
    }
}

/**
 * @brief 激活主窗口
 */
void SingleApplication::ActivateMainWindow()
{
    if(g_ptrWidget)
    {
   		//该句可以不加
        g_ptrWidget->setWindowState(g_ptrWidget->windowState() & ~Qt::WindowMinimized);
        
        g_ptrWidget->raise();
        g_ptrWidget->activateWindow();
    }
}

/**
 * @brief 收到新的连接
 */
void SingleApplication::slotNewPendingConnection()
{
    QLocalSocket *ptrSocket = m_ptrServer->nextPendingConnection();
    if(ptrSocket)
    {
        ActivateMainWindow();
        delete ptrSocket;
    }
}

main.cpp

#include "SingleApplication.h"
#include "MainWidget.h"

int main(int argc, char *argv[])
{
	SingleApplication a(argc, argv);
	if(a.IsRunning())
	{
		return 0;
	}
	
	MainWidget w;
	a.g_ptrWidget = &w;
	return a.exec();
}