Qt 5 : update QProgressBar during QThread work via signal

Question

I\'m trying to update a QProgressDialog (owned by a QMainWindow class) along the execution of a QThread who process some time consuming operations. The thread emit some sign

Answer 1

Absolutely wrong using of QThread). See what is the correct way to implement a QThread... (example please...). You need to learn thread's basics.

Your mistakes:
1. Create a static thread object in a local scope;
2. Wait for its finish in the main thread;
3. Don't start the thread;
4. Direct call method doHeavyCaclulations() in the main thread;
5. emit signal without working event loop for its deliver...

For your purpose you need:
Don't inherit QThread. Just create simple Work class with the necessary function:

class Work: public QObject
{
    Q_OBJECT

public:
    Work(){};
    virtual ~Work(){};

public slots:
    void doHeavyCaclulations() { /* do what you need and emit progress signal */ };

signals: 
    void progress(int);                
}

// Then:
void QApp::doSomeWork()
{
    //...
    QThread* thread = new QThread(parent);
    Work* worker = new Work; // Do not set a parent. The object cannot be moved if it has a parent. 
    worker->moveToThread(thread);

    connect(thread, SIGNAL(finished()), worker, SLOT(deleteLater()));
    connect(thread, SIGNAL(started()), worker, SLOT(doHeavyCaclulations()));
    connect(worker, SIGNAL(progress(int)), &progressDialog, SLOT(setValue(int)));

    thread->start();        
    //...
}