Launching a while-loop freezes program even if using another thread

Question

In my (Qt-)program I need a continuous request of a value which I get from an external source. But I did not want that this request freezes the whole program, so I created a separate thread for this function. But even if it is running in a separate thread, the GUI freezes, too. Why?

Code for the request function:

void DPC::run()
{
    int counts = 0, old_counts = 0;
    while(1)
    {
        usleep(50000);
        counts = Read_DPC();
        if(counts != old_counts)
        {
            emit currentCount(counts);
            old_counts = counts;
        }

    }
}

Read_DPC() returns an int value I want to sent to a lineEdit in my GUI.
The main class looks like

class DPC: public QThread
{
    Q_OBJECT
public:
    void run();
signals:
    void currentCount(int);
};

This code is called in the main function as:

DPC *newDPC = new DPC;
connect(newDPC, SIGNAL(currentCount(int)), SLOT(oncurrentCount(int)));
connect(newDPC, SIGNAL(finished()), newDPC, SLOT(deleteLater()));
newDPC->run();

How can I prevent this code from freezing my GUI? What am I doing wrong? Thanks!

Answer 1

It seems that you code run in GUI thread because you use run() method to start thread, so try to call start() as documentation and many examples said.

Try:

DPC *newDPC = new DPC;
connect(newDPC, SIGNAL(currentCount(int)), SLOT(oncurrentCount(int)));
connect(newDPC, SIGNAL(finished()), newDPC, SLOT(deleteLater()));
newDPC->start();//not run

Anyways you can call thread() method or currentThread() to see in which thread some objects live.