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How to put a function to a new thread? (Display video with OpenCv) Multiple Errors :-(
RolBri last edited by
I am a beginner with basic C++ knowledge.
I really like Qt Creater and I want to learn the own Qt languge.
Sadly for this time is missing a the moment :-(
I would like to display a Webcam stream in a own thread.
Because of using QtSerialPort I had to instantiate a QApplication and therefore I now have problems creating threads.
Is there a possibility to create a QApplication just for the QtSerialPort functions that there is no special Qt stuff necessary in the rest of the program?
I get multiple errors:
QObject::moveToThread: Widgets cannot be moved to a new thread
QObject: Cannot create children for a parent that is in a different thread.
QSocketNotifier: Can only be used with threads started with QThread
QObject::startTimer: Timers can only be used with threads started with QThread
This is the minmal I used:
using namespace std;
using namespace cv;
void DisplayWebCam ()
VideoCapture cap (0);
while(char(waitKey(10)) != 'q' && cap.isOpened())
cap >> frame;
int main (int argc, char *argv)
QApplication app(argc, argv); InitialiseSerialPort(); serial.write("Test"); serial.flush(); //DisplayWebCam(); //Works! thread t1 (DisplayWebCam); //Works not! t1.join(); return 0;
How can I solve my problem?
Thank you very much :-)
Hi and welcome to devnet,
Short version: widget and GUI related stuff must be done in the GUI thread AKA main thread.
OpenCV also has a Qt backend for its GUI, hence the errors you are seeing.
Since your knowledge of C++ is currently limited, you should avoid starting directly with threads, it's one of the very complex part of programming.