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QLocalSocket + QLocalServer

逻辑：首先一个新的实例启动时，将尝试连接到同一个本地服务器，如果连接失败，则表示第一个实例进程，创建一个本地服务器；否则，拉起已打开的实例进程。

main.cpp

#include <QApplication>
#include "main_windows.h"
#include "single_application.h"//QT启动屏蔽cmd
#pragma comment(linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"")int main(int argc, char* argv[])
{//QApplication a(argc, argv);SingleApplication singleApplication(argc, argv);if (!singleApplication.IsRunning()){MainWindow mainWindow;mainWindow.show();singleApplication.m_mainWindow = &mainWindow;return SingleApplication::exec();}return 0;
}

single_application.h

//
// Created by zhe.xiao on 2024/3/1.
//#pragma once#include <QApplication>
#include <QWidget>
#include <QLocalServer>
#include <QLocalSocket>class SingleApplication : public QApplication
{
Q_OBJECT
public:SingleApplication(int& argc, char* argv[]);//是否已有实例在运行bool IsRunning();private://初始化本地连接void InitLocalConnection();//创建服务端void CreateLocalServer();//激活窗口void ActivateWindow();public://MainWindow指针QWidget* m_mainWindow;private://运行状态bool m_isRunning;//是否已有实例在运行QLocalServer* m_localserver;//本地socket ServerQString m_applicationName;//连接超时时间int m_timeout = 1000;private slots://有新连接时触发void OnNewConnection();
};

single_application.cpp

//
// Created by zhe.xiao on 2024/3/1.
//#include <QFileInfo>
#include "single_application.h"
#include <QDebug>SingleApplication::SingleApplication(int& argc, char* argv[]) : QApplication(argc, argv)
{m_isRunning = false;m_mainWindow = nullptr;m_localserver = nullptr;m_applicationName = QFileInfo(QApplication::applicationFilePath()).fileName();qDebug() << "m_serverName:" << m_applicationName;InitLocalConnection();
}/*** 通过socket通讯实现程序单实例运行，* 初始化本地连接，如果连接不上server，则创建，否则退出*/
void SingleApplication::InitLocalConnection()
{m_isRunning = false;//尝试连接本地服务器，如果连上了就触发OnNewConnection，QLocalSocket socket;socket.connectToServer(m_applicationName);if (socket.waitForConnected(m_timeout)){m_isRunning = true;return;}//首次打开exe连接不上，则需要先创建一个本地服务器CreateLocalServer();
}void SingleApplication::CreateLocalServer()
{m_localserver = new QLocalServer(this);connect(m_localserver, &QLocalServer::newConnection, this, &SingleApplication::OnNewConnection);if (!m_localserver->listen(m_applicationName)){// 此时监听失败,可能是程序崩溃时,残留进程服务导致的,移除if (m_localserver->serverError() == QAbstractSocket::AddressInUseError){QLocalServer::removeServer(m_applicationName);m_localserver->listen(m_applicationName); //重新监听}}
}/*** 通过socket通讯实现程序单实例运行,监听到新的连接【即重新双击exe】时触发该函数.*/
void SingleApplication::OnNewConnection()
{QLocalSocket* localSocket = m_localserver->nextPendingConnection();if (localSocket){localSocket->waitForReadyRead(m_timeout * 2);delete localSocket;//激活窗口ActivateWindow();}
}void SingleApplication::ActivateWindow()
{if (m_mainWindow != nullptr){m_mainWindow->raise();m_mainWindow->showNormal();m_mainWindow->activateWindow();}
}bool SingleApplication::IsRunning()
{return m_isRunning;
}