How to continually run QProcess while running my QML program? - qt

Question

The problem I have in my code is, once the QML engine uplouded the QProcess stop!! Is it possible to let QProcess run while the QMLis already in operation!
the idea is: I want the user to be able to interact with only one specific mouse and one keyboard and to continually check this condition!
Can some one check what is the problem here?
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
bool scanForDevices=0;
USBdeviceID *usbdeviceid =new USBdeviceID();
engine.rootContext()->setContextProperty("USBdeviceID", usbdeviceid);
QProcess OProcess;
QString Command; //Contains the command to be execute
Command = "lsusb";
while (1)
{
OProcess.start(Command,QIODevice::ReadOnly); //Starts execution of command
OProcess.waitForFinished(); //Waits for execution to complete
QString StdOut = OProcess.readAllStandardOutput(); //Reads standard output
QString StdError = OProcess.readAllStandardError(); //Reads standard error
cout<<"\n Printing the standard output..........\n";
cout<<endl<<StdOut.toStdString();
bool mouse1 = StdOut.contains("ID 046d:c03e");
bool keyBoard1 = StdOut.contains("ID 413c:1003");
if (mouse1 ==1 && keyBoard1==1)
{
// start main program
// revoke A signal to tell QML the correct devices are connected
usbdeviceid->setMouse1Detected(1);
usbdeviceid->setkeyBoard1Detected(1);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
}
}
}

Answer 1

It is not necessary to create infinite loops in Qt, instead the most elegant thing is to use the signals.
#include <QGuiApplication>
#include <QProcess>
#include <QQmlApplicationEngine>
class LSUSB: public QObject
{
Q_OBJECT
public:
LSUSB(const QStringList & ids, QObject *parent=nullptr): QObject(parent), status(false), ids(ids)
{
QString command = "lsusb";
connect(&process, &QProcess::readyReadStandardOutput, this, &LSUSB::onReadyReadStandardOutput);
connect(&process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this, &LSUSB::onFinished);
process.setProgram(command);
process.start();
}
Q_SIGNALS:
void isLoaded();
private Q_SLOTS:
void onReadyReadStandardOutput(){
QString stdout = process.readAllStandardOutput();
status = true;
for(const QString & id: ids){
status &= stdout.contains(id);
}
if(status){
process.kill();
Q_EMIT isLoaded();
}
}
void onFinished(){
if(!status)
process.start();
}
private:
QProcess process;
bool status;
QStringList ids;
};
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
LSUSB lsusb({"ID 046d:c03e", "ID 413c:1003"});
USBdeviceID usbdeviceid;
QObject::connect(&lsusb, &LSUSB::isLoaded, [&engine, &usbdeviceid](){
usbdeviceid.setMouse1Detected(1);
usbdeviceid.setkeyBoard1Detected(1);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
QCoreApplication::exit(-1);
});
return app.exec();
}
#include "main.moc"