从另一个非GUI线程启动QTimer

Question

I try to start QTimer from another thread ( to get better accuracy ).

I think that problem is with function connect but let see my code:

//code from constructor of parent.cpp class
{
    //run_clock_timer(this); // this works

    std::thread t1{ [this] { run_clock_timer(this); } }; //not works
    t1.join();
}

And function:

void class::run_clock_timer(class* inst){
    QTimer * test = new QTimer(inst);
    connect(test, SIGNAL(timeout()), inst, SLOT(updateTime()));
    test->setInterval(50);
    test->start(timer_precision);
}

Debugger told me that code from run_clock_timer was run, but no result.

I think i will do it with no problem when i use QThread, but i want to use std::thread.

So whats wrong with my function ?

Answer 1

The problem is that QTimer depends on the ability to interact with a running Qt event loop in order to perform its task. Since a non-Qt thread has no event loop, the QTimer can't do its job. (ie there has to be some Qt code running in the thread, that will emit the timeout() signal, that doesn't just happen on its own)