Camera class in QThread

stryga42

I think the problem is that you call run directly from your GUI thread - this is a simple (blocking) call, not the start of a new thread. You should call start() on your camera object, I guess.
Edit: Your have two QThread objects - cameraThread and camera (which is derived from QThread) why? You mix the two options to use QThread (moving a worker object to QThread or reimplementing QThread::run(). )

Creatorczyk

@stryga42 If I change the inheritance from QThread to QObject, nothing will change

Christian Ehrlicher

@Creatorczyk Since you don't start the thread anywhere nothing happens.

Creatorczyk

@Christian-Ehrlicher I change code in main.cpp to:

QThread cameraThread;
    Camera *camera = new Camera();
    QObject::connect(camera, &Camera::FrameReady, mqttClient, &MqttClient::sendFrame);
    camera->moveToThread(&cameraThread);
    cameraThread.start();
    camera->run();
    qDebug()<<"Started";   //Will not be done
    camera->stop();   //Will not be done
    qDebug()<<"Stopped";   //Will not be done

Unfortunately nothing happened. Futher code does not execute

Christian Ehrlicher

@Creatorczyk Again: you don't start your thread anywhere, you just call a function named run() in your Camera object - nothing more.

Creatorczyk

@Christian-Ehrlicher calling "cameraThread.start();" will not start thread?

Christian Ehrlicher

@Creatorczyk It will, but then you call a blocking function in your main thread.

stryga42

@Creatorczyk

cameraThread.start();

is the right thing to do. Yes, this starts a new thread "within" the object cameraThread. This call to start() does not block. Check it it out by inserting a qDebug() output right after the call.
But then you call (unnecessarily) Camera::run(), which will block. Use signals to "trigger" your camera object. Again, I think you mix up the two ways to use QThread: Usually you EITHER use the "moveToTrhread-style" OR the "reimplement QThread::run-style", but not both at the same time. If you want your code in Camera::run() to be executed without signaling, you have to call start() on your (then QThread derived) Camera object. Som thing like

camera->start();

should do the job. cameraThread is then not required at all.

jsulm

@Creatorczyk said in Camera class in QThread:

calling "cameraThread.start();" will not start thread?

Did you read https://doc.qt.io/qt-5/qthread.html#start ?
start() calls run() - you do not have to call run() by yourself and you should NOT!

Creatorczyk

@stryga42 @Christian-Ehrlicher @jsulm Thanks, I fixed it!