How to Restart Qt Application

Posted 2020-10-29

How to restart QtApplication

As we know, Restarting Application means to exit current application, then to call another application. So, let‘s see how exit of one application.

Qt Application

int main(int argc, char** argv)
{
    QApplication app(argc, argv);
    Widget w;
    w.show()
    return app.exec();
}

The code snippet,last line return app.exec() let Qt application in main event loop. if you want to exit main event loop, Just callQCoreApplication::exit(int); or QCoreApplication::quit();

QApplication has one property called quitOnLastWindowClosed, it means the application will exit after last window closed.

About how to close all windows, we can use QApplication::closeAllWindows(), It is better way for using quit to exit application. That way, We can let all windows object revice close event, and do some thing before destroy.

Call another Application

In Qt, It is better let QProcess to do this. It let another application to run and not has father-son relationship.

QProcess::startDetached(qApp->applicationFilePath(), QStringList());

if applicationFilePath not continues space char, we can use

QProcess::startDetached(qApp->applicationFilePath());

Example one

qApp->quit();
QProcess::startDetached(qApp->applicationFilePath(), QStringList());

or

qApp->closeAllWindow();
QProcess::startDetached(qApp->applicationFilePath(), QStringList());

Example two

/**773 = 'r'+'e'+'s'+'t'+'a'+'r'+'t' */
qApp->exit(773);

int main(int argc, char** argv)
{
    int ret = app.exec();
    if (ret == 773) {
        QProcess::startDetached(qApp->applicationFilePath(), QStringList());
        return 0;
    }
    return ret;
}

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