How do I create a pause wait function using Qt

Question

I m playing around with Qt  and I want to create a simple pause between two commands  However it won t seem to let me use Sleep int mili    and I can t find any obvious wait functions   I am basically just making a console application to test some class code which will later be included in a proper Qt GUI  so for now I m not bothered about breaking the whole event-driven model

User · Answer

Small  1 to kshark27 s answer to make it dynamic    include  lt QTime gt   void delay  int millisecondsToWait         QTime dieTime   QTime  currentTime   addMSecs  millisecondsToWait        while  QTime  currentTime    lt  dieTime                 QCoreApplication  processEvents  QEventLoop  AllEvents  100

User · Answer

I wrote a super simple delay function for an application I developed in Qt   I would advise you to use this code rather than the sleep function as it won t let your GUI freeze   Here is the code   void delay         QTime dieTime  QTime  currentTime   addSecs 1       while  QTime  currentTime    lt  dieTime          QCoreApplication  processEvents QEventLoop  AllEvents  100       To delay an event by n seconds - use addSecs n

User · Answer

I ve had a lot of trouble over the years trying to get QApplication  processEvents to work  as is used in some of the top answers   IIRC  if multiple locations end up calling it  it can end up causing some signals to not get processed  https   doc qt io archives qq qq27-responsive-guis html    My usual preferred option is to utilize a QEventLoop  https   doc qt io archives qq qq27-responsive-guis html waitinginalocaleventloop    inline void delay int millisecondsWait        QEventLoop loop      QTimer t      t connect  amp t   amp QTimer  timeout   amp loop   amp QEventLoop  quit       t start millisecondsWait       loop exec

User · Answer

we can use following method QT Delay   QTimer  singleShot 2000 this SLOT print lcd        This will wait for 2 seconds before calling print lcd

User · Answer

Similar to some answers here  but maybe a little more lightweight  void MyClass  sleepFor qint64 milliseconds       qint64 timeToExitFunction   QDateTime  currentMSecsSinceEpoch   milliseconds      while timeToExitFunction gt QDateTime  currentMSecsSinceEpoch             QApplication  processEvents QEventLoop  AllEvents  100

User · Answer

From Qt5 onwards we can also use  Static Public Members of QThread  void    msleep unsigned long msecs  void    sleep unsigned long secs  void    usleep unsigned long usecs

User · Answer

We ve been using the below class -  class SleepSimulator       QMutex localMutex       QWaitCondition sleepSimulator  public      SleepSimulator  SleepSimulator                 localMutex lock              void sleep unsigned long sleepMS                sleepSimulator wait  amp localMutex  sleepMS             void CancelSleep                 sleepSimulator wakeAll               QWaitCondition is designed to coordinate mutex waiting between different threads   But what makes this work is the wait method has a timeout on it   When called this way  it functions exactly like a sleep function  but it uses Qt s event loop for the timing   So  no other events or the UI are blocked like normal windows sleep function does   As a bonus  we added the CancelSleep function to allows another part of the program to cancel the  sleep  function   What we liked about this is that it lightweight  reusable and is completely self contained   QMutex  http   doc qt io archives 4 6 qmutex html  QWaitCondition  http   doc qt io archives 4 6 qwaitcondition html

User · Answer

This previous question mentions using qSleep   which is in the QtTest module  To avoid the overhead linking in the QtTest module  looking at the source for that function you could just make your own copy and call it  It uses defines to call either Windows Sleep   or Linux nanosleep      ifdef Q OS WIN  include  lt windows h gt     for Sleep  endif void QTest  qSleep int ms        QTEST ASSERT ms  gt  0     ifdef Q OS WIN     Sleep uint ms     else     struct timespec ts     ms   1000   ms   1000    1000   1000        nanosleep  amp ts  NULL    endif

User · Answer

Since you re trying to  test some class code   I d really recommend learning to use QTestLib  It provides a QTest namespace and a QtTest module that contain a number of useful functions and objects  including QSignalSpy that you can use to verify that certain signals are emitted   Since you will eventually be integrating with a full GUI  using QTestLib and testing without sleeping or waiting will give you a more accurate test -- one that better represents the true usage patterns  But  should you choose not to go that route  you could use QTestLib  qSleep to do what you ve requested   Since you just need a pause between starting your pump and shutting it down  you could easily use a single shot timer   class PumpTest  public QObject       Q OBJECT     Pump  amp pump  public      PumpTest Pump  amp pump  pump pump      public slots      void start     pump startpump          void stop     pump stoppump          void stopAndShutdown             stop            QCoreApplication  exit 0             void test             start            QTimer  singleShot 1000  this  SLOT stopAndShutdown              int main int argc  char  argv          QCoreApplication app argc  argv       Pump p      PumpTest t p       t test        return app exec        But qSleep   would definitely be easier if all you re interested in is verifying a couple of things on the command line   EDIT  Based on the comment  here s the required usage patterns   First  you need to edit your  pro file to include qtestlib   CONFIG    qtestlib   Second  you need to include the necessary files    For the QTest namespace  which includes qSleep    include  lt QTest gt  For all the items in the QtTest module   include  lt QtTest gt   This is functionally equivalent to adding an include for each item that exists within the namespace

User · Answer

To use the standard sleep function add the following in your  cpp file    include  lt unistd h gt    As of Qt version 4 8  the following sleep functions are available   void QThread  msleep unsigned long msecs  void QThread  sleep unsigned long secs  void QThread  usleep unsigned long usecs    To use them  simply add the following in your  cpp file    include  lt QThread gt    Reference  QThread  via Qt documentation   http   doc qt io qt-4 8 qthread html  Otherwise  perform these steps     Modify the project file as follows   CONFIG    qtestlib   Note that in newer versions of Qt you will get the following error   Project WARNING  CONFIG  qtestlib is deprecated  Use QT  testlib instead        so  instead modify the project file as follows   QT    testlib   Then  in your  cpp file  be sure to add the following    include  lt QtTest gt    And then use one of the sleep functions like so   usleep 100

User · Answer

kshark27 s answer didn t work for me for some reason  because I use Qt 5 7   so I ended up doing this   while  someCondition           do something     QApplication  processEvents       QThread  sleep 1      1 second       If this is done in the GUI thread  it obviously introduces a 1 second GUI lag before responding to user events  But if you can live with it  this solution is probably an easiest to implement and even Qt endorses it in their Threading Basics article  see When to Use Alternatives to Threads section

User · Answer

If you want a cross-platform method of doing this  the general pattern is to derive from QThread and create a function  static  if you d like  in your derived class that will call one of the sleep functions in QThread

[c++] How do I create a pause/wait function using Qt?

Examples related to c++

Examples related to qt

Examples related to sleep

Examples related to wait