Qt 运行一个实例进程

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

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#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

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//
// 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 Server
    QString 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

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//
// 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;
}