[SOLVED] QProcess Java Application Not Working

[stampede]

QProcess will start your command asynchronously, you'll have to wait before checking if its running or any error occured. From Qt docs:

Processes are started asynchronously, which means the started() and error() signals may be delayed. Call waitForStarted() to make sure the process has started (or has failed to start) and those signals have been emitted.

[2lights]

Tried multiple methods but to no avail

Are there any #includes I should add to my .cpp file to call function
My function just initializes the the QProcess as above and tries to run it

Do I need to create a Java virtual machine before I try calling QProcess

Is there any simple tutorial I can follow?

Kind Regards

[stampede]

My function just initializes the the QProcess as above and tries to run it

And it does not wait for it to start and does not check for error values.

{
// ...
QProcess *myProcess = new QProcess(this);
connect(myProcess, SIGNAL(error(QProcess::ProcessError)), this, SLOT(checkError(QProcess::ProcessError)));
connect(myProcess, SIGNAL(started()), this, SLOT(processStarted()));
connect(myProcess, SIGNAL(finished(int, QProcess::ExitStatus)), this, SLOT(processExited(int,QProcess::ExitStatus)));
myProcess->start(program, arg);
// .. here you exit the current function and wait for process to start / fail to start
}
 
void MyClass::processStarted(){
    qDebug() << "Hurray ! MyProcess started!";
}
 
void MyClass::checkError(QProcess::ProcessError err){
    qDebug() << "Process error: " << err;
}
 
void MyClass::processExited(int exitCode, QProcessExitStatus status){
    qDebug() << "Process exited with code: " <<exitCode << ", status: " << status;
}

{
// ...
QProcess *myProcess = new QProcess(this);
connect(myProcess, SIGNAL(error(QProcess::ProcessError)), this, SLOT(checkError(QProcess::ProcessError)));
connect(myProcess, SIGNAL(started()), this, SLOT(processStarted()));
connect(myProcess, SIGNAL(finished(int, QProcess::ExitStatus)), this, SLOT(processExited(int,QProcess::ExitStatus)));
myProcess->start(program, arg);
// .. here you exit the current function and wait for process to start / fail to start
}

void MyClass::processStarted(){
    qDebug() << "Hurray ! MyProcess started!";
}

void MyClass::checkError(QProcess::ProcessError err){
    qDebug() << "Process error: " << err;
}

void MyClass::processExited(int exitCode, QProcessExitStatus status){
    qDebug() << "Process exited with code: " <<exitCode << ", status: " << status;
}

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Alternative is to call waitForFinished() after start(), but this can freeze the gui.
It is important to understand the asynchronous nature of QProcess, this:

QProcess *myProcess = new QProcess(this);
    myProcess->start(program, arg);
 
    qDebug() << myProcess->state();   //Ref 1
    qDebug() << myProcess->error();   //Ref 2

QProcess *myProcess = new QProcess(this);
    myProcess->start(program, arg);
 
    qDebug() << myProcess->state();   //Ref 1
    qDebug() << myProcess->error();   //Ref 2

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will not work correctly in most of the cases, because you check the status and error value of QProcess before it is initialized and started.