Qt 防多开

防止多开传统的做法有文件锁(如Eclipse的.lock文件), 进程间通信等.

但是使用文件锁方式原实例无法知晓有新实例试图启动, 从而置顶自己的窗口.

进程间通信可以使用共享内存. 如使用启动中的腾讯qq来登录qq音乐.也可以使用server, socket这样讨巧的方法

Qt本身没有提供一个跨平台的防多开解决方案, 官方推荐的QSingleApplication解决方案并不包含在Qt的library中,并且貌似是遵从商业协议而非社区版本. 所以需要我们自己来实现一个.

使用共享内存和文件锁的一个缺点是,程序一旦异常退出, 可能导致下一次无法正常启动 (还记得要去手动删除Eclipse的.lock文件的时候吧)

而使用QLocalServer和QLocalSocket结合QSharedMemory可以很好的实现多开的检查以及对先前实例的唤醒.

参考链接:http://www.qtcentre.org/wiki/index.php?title=SingleApplication#Introduction

我的实际例子

// singleApplication.h

#ifndef SINGLEAPPLICATION_H

#define SINGLEAPPLICATION_H

#include <QApplication>

#include <QSharedMemory>

#include <QLocalServer>

#include "dlgmain.h"

class SingleApplication : public QApplication

{

    Q_OBJECT

public:

    explicit SingleApplication(int &argc, char* argv[], const QString uniqueKey);

    bool isRunning();

    bool sendMessage(const QString & message);

public slots:

    void receiveMessage();

    void showMainWindow();

signals:

    void messageAvailable(QString message);

private:

    bool _isRunning;

    QString _uniqueKey;

    QSharedMemory sharedMemory;

    QLocalServer* localServer;

    static const int timeout = 1000;

};

#endif // SINGLEAPPLICATION_H

// singleApplication.cpp

#include "singleapplication.h"

#include <QLocalSocket>

/*

 * CONSTRUCTION: set SingleApplication's shareMemory key to <uniqueKey>

 * test attach , if success, already has an instance running

 * if not running, use shareMemory to create a segment in the memory

 * new a server to listem for <uniqueKey>, once received, hand over to SLOT(receiveMessage())

 *

 */

SingleApplication::SingleApplication(int &argc, char* argv[], const QString uniqueKey) :

    QApplication(argc, argv), _uniqueKey(uniqueKey)

{

    sharedMemory.setKey(_uniqueKey);

    if(sharedMemory.attach()){

        _isRunning = true;

    }

    else{

        _isRunning = false;

        if(!sharedMemory.create(1)){

            qDebug()<<"Unable to create single instance";

            return;

        }

        // create local server and listener to incomming message from other instances.

        localServer = new QLocalServer(this);

//        connect(localServer, SIGNAL(newConnection()), this, SLOT(receiveMessage()));

        connect(localServer, SIGNAL(newConnection()), this, SLOT(showMainWindow()));

        localServer->listen(_uniqueKey);

    }

}

// public slot

/*

 * RECIVER: waiting for connection.once get one connection, create a socket to communicate with the client.

 *

 */

void SingleApplication::receiveMessage(){

    qDebug()<<"receiveMessage";

    QLocalSocket* localSocket = localServer->nextPendingConnection();

    if(!localSocket->waitForReadyRead(timeout)){

        qDebug()<<"localSocket waitForReadyRead failed.";

        qDebug()<<localSocket->errorString().toLatin1();

        return;

    }

    QByteArray byteArray = localSocket->readAll();

    QString message = QString::fromUtf8(byteArray.constData());

    emit messageAvailable(message);

    localSocket->disconnectFromServer();

}

void SingleApplication::showMainWindow(){

    QLocalSocket *localSocket = localServer->nextPendingConnection();

    if (!localSocket)

        return;

    delete localSocket;

    DlgMain::shareInstance()->show();

}

// public functions;

bool SingleApplication::isRunning(){

    qDebug()<<"SingleApplication is running? "<<_isRunning;

    return _isRunning;

}

/*

 * SENDER: if there is already a instance running, create a Socket to communicate with It's Server.

 *

 */

bool SingleApplication::sendMessage(const QString &message){

    qDebug()<<"sendMessage";

    if(!_isRunning){

        return false;

    } // no instance, do nothing.

    QLocalSocket localSocket(this);

    localSocket.connectToServer(_uniqueKey, QIODevice::WriteOnly);

    if(!localSocket.waitForConnected(timeout)){

        qDebug()<<"waitForConnected";

        qDebug()<<localSocket.errorString().toLatin1();

        return false;

    }

    if(!localSocket.waitForBytesWritten(timeout)){

        qDebug()<<"waitForBytesWritten";

        qDebug()<<localSocket.errorString().toLatin1();

        return false;

    }

    localSocket.disconnectFromServer();

    return true;

}

使用方式:(直接把上面的类拷去用就行,)

// 注意一下main.cpp的调用以及槽的使用就行

#include "dlglogin.h"

#include "singleapplication.h"

int main(int argc, char *argv[])

{

    SingleApplication app(argc, argv, "CocosPlay");

    if(app.isRunning()) {

        app.sendMessage("call");

        return 0;

    }

    QObject::connect(&app, SIGNAL(messageAvailable(QString)), &app, SLOT(showMainWindow()));

    DlgLogin* mainWindow = DlgLogin::shareInstance();

    mainWindow->show();
    mainWindow->on_btnLogin_clicked();

    return app.exec();

}