CODEWITHSUNDEEP
c++qt
miqelm
miqelm

Reputation: 354

Qt C++ QTimer does not call handler

I've got problem with QTimer in Qt C++, in my code timeoutHandler() is not called. Can anyone tell me why and how I can fix it?

Test.h

class Test : public QObject
{
    Q_OBJECT
private:
    static bool timeOuted;
public:
    explicit Test(QObject *parent = 0);
    virtual ~Test();
public slots:
    static void handleTimeout();
};

Test.cpp

void Test::run()
{
    QTimer::singleShot(3000, this, SLOT(handleTimeout()));
    while(!timeOuted);
    if(timeOuted)
    {
        timeOuted = false;
    }
    else
    {
       /* some work */
    }
}

bool Test::timeOuted = false;

void Test::handleTimeout()
{
    static int i = 0;
    timeOuted = true;
    qDebug() << "TimeOuted " << i++;
}

Upvotes: 1

Views: 1459

Answers (2)

user4193134
user4193134

Reputation:

To update answer from Googie you can use also lambda from C++11:

QTimer::singleShot(10000, [=]() {
            // Handle timeout here
});

Upvotes: 1

Googie
Googie

Reputation: 6017

QTimer requires Qt event loop to work. When you enter the while(!timeOuted);, you block the current thread endlessly and the Qt's event loop has no chance to take any action (like calling your handler for the timer). Here's how you should do it:

Test.h:

class Test : public QObject
{
    Q_OBJECT
public:
    explicit Test(QObject *parent = 0);
    virtual ~Test();

    void run(); // <-- you missed this
private slots: // <-- no need to make this slot public
    void handleTimeout(); // <-- why would you make it static?!
};

Test.cpp:

void Test::run()
{
    QTimer::singleShot(3000, this, SLOT(handleTimeout()));
}

void Test::handleTimeout()
{
    static int i = 0;
    qDebug() << "TimeOuted " << i++;

    /* some work */
}

Upvotes: 6

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