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Thread: QTimer in QThread working in ubuntu but not working in windows

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    Question QTimer in QThread working in ubuntu but not working in windows

    Qtimer timeout slot is executing in linux but not working in windows showing

    QObject::startTimer: timers cannot be started from another thread

    help me if anybody knows. Thanks in advance....
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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    Create the timer in the run() method of the thread.
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  3. The following user says thank you to wysota for this useful post:

    pradeepreddyg95 (24th September 2012)

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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    hi wysota, I tried that method also same warning is coming but my confusion is same thing is working under ubuntu can u plz check the sample test code ...

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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    Two things you are missing

    1. Event loop is not being ececuted. (i.e exec(), this is required, else the thread will exit)
    2. Timer should started from the parent thread , i.e the ctor() and run() functions execute in different thread context hence the object created on ctor() should be moved the the the thread, or other way is to create the timer in run() method (as wysota said)
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  6. The following user says thank you to Santosh Reddy for this useful post:

    pradeepreddyg95 (24th September 2012)

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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    Thanks Santosh,
    But in ubuntu i am using like this
    void Thread::run()
    {
    while(1)
    {
    // some operations doing inside the loop
    if(m_pProbeFailure[i].Value > m_nCuurrent_ADC_Value)
    {
    if(!m_pTimer[i].isActive())
    m_pTimer[i].start();
    }

    }

    }
    like this iam using without calling exec() it working fine but in windows not working ... Plz solve my issue .... if any body ...

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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    QTimer will works when you have have a event loop (i.e. call exec());, or other way is to explictily process the events by calling QCoreApplication:rocessEvents(), from the local while loop.

    Qt Code:
    1. void Thread::run()
    2. {
    3. while(1)
    4. {
    5. // some operations doing inside the loop
    6. if(m_pProbeFailure[i].Value > m_nCuurrent_ADC_Value)
    7. {
    8. if(!m_pTimer[i].isActive())
    9. m_pTimer[i].start();
    10. }
    11. QCoreApplication::processEvents();
    12. }
    13. }
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    When you don't know how to do it then it is not that you may do it wrong but you may not do it right.

  9. The following user says thank you to Santosh Reddy for this useful post:

    pradeepreddyg95 (24th September 2012)

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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    Thanks Santosh its working .....


    Added after 16 minutes:


    hi Santosh But iam unable to stop timers after timeout showing the following msg

    void Thread::TimerTimeOut()
    {
    qDebug() << "TimerTimeOut " << sender()->objectName();

    QTimer *pTimer = qobject_cast<QTimer*>(sender());
    pTimer->stop();
    }

    TimerTimeOut "Timer1"
    QObject::killTimer: timers cannot be stopped from another thread
    Last edited by pradeepreddyg95; 24th September 2012 at 07:27.

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    Default Re: QTimer in QThread working in ubuntu but not working in windows

    You cannot create the timer in one thread and operate it from another: there is no new error or problem here and the error message tells you exactly where the problem lies.
    • If the timer exists in the main thread then it can be started and stopped from code executing in the main thread only.
    • If the timer exists in the a secondary thread then it can be started and stopped from code executing in the secondary thread only.
    • Same goes for the third, fourth, fifth ...

    You ask us to solve your problem when you have failed to take on board the information already supplied.

    In your original code: code in the Thread class constructor executes in the main thread creating a timer in that thread. Code in the run() function runs in the controlled thread. Thus the pTimer is in one thread, and the pTimer->Start() is in another and never the two shall meet.
    Last edited by ChrisW67; 24th September 2012 at 08:22.

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    pradeepreddyg95 (24th September 2012)

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