[Interest] QEventLoop -- not sure I am correctly using this

Jason Kretzer Jason at gocodigo.com
Mon Dec 2 20:14:19 CET 2013

Good Day,

I have in my application, two classes.  When the application starts up, one of the classes -backgroundtaskmanager - gets instantiated.  In the constructor, a QTimer is started to timeout every 5 minutes and call runTasks.  The instantiation is then moved to a separate thread so that it can run without impacting the rest of the application.

Here are the contents of the constructor.

QTimer* timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(runTasks()));
    timer->start(300000); //fiveminutes
    thread = new QThread();

The second class -player- is instantiated in the main thread.  Once it is instantiated, it begins doing other tasks.  Basically, a method is called with the following code.  This code is designed to make the while loop delay for one second before executing the rest of the loop (one second-ish, I know it is not perfect but it has good enough resolution for what I need).

while(!taskQueue.isEmpty()) {
        qDebug() << “BEFORE QEVENTLOOP”;
QEventLoop wait1Sec;
        QTimer::singleShot(1000, &wait1Sec,SLOT(quit()));

QList<Task*> instances;
 for(int t=seconds; t>previousTime; t—) {
  QList<Task*> vals = taskQueue.values(t);
 while(!vals.isEmpty()) {
 instances.insert(0, vals.takeLast());
 previousTime = seconds;
 miliSeconds = QDateTime::currentMSecsSinceEpoch() - today.toMSecsSinceEpoch();
 seconds = miliSeconds/1000;

NOTE:  the two sets of tasks these do are not related.

So, anyway, every 5 minutes the tasks in backgroundtaskmanager are run.  Some of these tasks can take up to a minute.  When the backgroundtaskmanager class runs a task that does take this long (remember it is in a separate thread), the player class code above gets hung in what appears to be the inside of the QEventLoop.  The qDebug statements don’t write out until the tasks in the backgroundtaskmanager are finished.  Then it rushes through to catch up.

My question is, am I correctly doing this at all?  Is this the proper use of a QEventLoop?



- - - - - - - - - - - - - - - - - - - - - - -
Jason R. Kretzer

Application Developer
Google # 606-887-9011
Cell # 606-792-0079
Jason at gocodigo.com<mailto:Jason at gocodigo.com>

“quidquid latine dictum sit altum videtur”

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