Update progress bar in another thread

[qt_developer]

Hi all,

I have an application with an additional thread that handles a heavy process for the purpose of the GUI doesn't lock.

In this process is needed update a progress bar that resides in the main thread but sometimes the application closes unexpectedly.

I get these messages in application output:

QObject::connect: Cannot queue arguments of type 'QTextBlock'
(Make sure 'QTextBlock' is registered using qRegisterMetaType().)
QObject::connect: Cannot queue arguments of type 'QTextCursor'
(Make sure 'QTextCursor' is registered using qRegisterMetaType().)
QObject::killTimers: timers cannot be stopped from another thread

How can I solve this issue?

My code:

#ifndef THREADMANAGER_H
#define THREADMANAGER_H
 
#include <QObject>
 
class QThread;
class GComputationWorker;
 
class ThreadManager: public QObject
    {
    Q_OBJECT
public:
    // constructors and destructor
    /**
     * Returns an instance of this class. When called for the first
     * time, a new instance is created and returned. After that,
     * calling InstanceL returns the same instance that was created
     * earlier.
     *
     * @return A pointer to a ThreadManager object
     */
    static ThreadManager* instance();
 
private:
    // constructor
    /**
     * Default constructor is private because we are using the
     * singleton design pattern.
     */
 
    ThreadManager();
 
public:
 
    void doComputationWork();
 
private:
 
    static ThreadManager *_instance;
 
    QThread              *computationThread;
 
    GComputationWorker   *computationWorker;
 
    };
 
#endif // THREADMANAGER_H

#ifndef THREADMANAGER_H
#define THREADMANAGER_H

#include <QObject>

class QThread;
class GComputationWorker;

class ThreadManager: public QObject
    {
    Q_OBJECT
public:
    // constructors and destructor
    /**
     * Returns an instance of this class. When called for the first
     * time, a new instance is created and returned. After that,
     * calling InstanceL returns the same instance that was created
     * earlier.
     *
     * @return A pointer to a ThreadManager object
     */
    static ThreadManager* instance();

private:
    // constructor
    /**
     * Default constructor is private because we are using the
     * singleton design pattern.
     */

    ThreadManager();

public:

    void doComputationWork();

private:

    static ThreadManager *_instance;

    QThread              *computationThread;

    GComputationWorker   *computationWorker;

    };

#endif // THREADMANAGER_H

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#include "threadmanager.h"
#include "gcomputationworker.h"
 
#include <QThread>
 
ThreadManager * ThreadManager::_instance = NULL;
 
ThreadManager::ThreadManager()
    {
    _instance = NULL;
    computationThread = new QThread;
    computationWorker = new GComputationWorker;
    computationWorker->moveToThread(computationThread);
    }
 
ThreadManager* ThreadManager::instance()
    {
    if (ThreadManager::_instance == 0)
        ThreadManager::_instance = new ThreadManager();
    return ThreadManager::_instance;
    }
 
void ThreadManager::doComputationWork()
    {
        computationOperFinished = false;
        computationThread->start();
        computationThread->setPriority(QThread::NormalPriority);
        QMetaObject::invokeMethod(computationWorker, "doWork", Qt::QueuedConnection);
    }

#include "threadmanager.h"
#include "gcomputationworker.h"

#include <QThread>

ThreadManager * ThreadManager::_instance = NULL;

ThreadManager::ThreadManager()
    {
    _instance = NULL;
    computationThread = new QThread;
    computationWorker = new GComputationWorker;
    computationWorker->moveToThread(computationThread);
    }

ThreadManager* ThreadManager::instance()
    {
    if (ThreadManager::_instance == 0)
        ThreadManager::_instance = new ThreadManager();
    return ThreadManager::_instance;
    }

void ThreadManager::doComputationWork()
    {
        computationOperFinished = false;
        computationThread->start();
        computationThread->setPriority(QThread::NormalPriority);
        QMetaObject::invokeMethod(computationWorker, "doWork", Qt::QueuedConnection);
    }

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#ifndef GCOMPUTATIONWORKER_H
#define GCOMPUTATIONWORKER_H
 
#include <QObject>
 
class GComputationWorker : public QObject
{
    Q_OBJECT
public:
 
    GComputationWorker();
 
    ~GComputationWorker();
 
public slots:
 
    void doWork();
};
 
#endif // GCOMPUTATIONWORKER_H

#ifndef GCOMPUTATIONWORKER_H
#define GCOMPUTATIONWORKER_H

#include <QObject>

class GComputationWorker : public QObject
{
    Q_OBJECT
public:

    GComputationWorker();

    ~GComputationWorker();

public slots:

    void doWork();
};

#endif // GCOMPUTATIONWORKER_H

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#include "gcomputationworker.h"
 
GComputationWorker::GComputationWorker()
{
}
 
GComputationWorker::~GComputationWorker()
{
}
 
void GComputationWorker::doWork()
{
    // Start computation
    // The progress bar is updated by setValue method
}

#include "gcomputationworker.h"

GComputationWorker::GComputationWorker()
{
}

GComputationWorker::~GComputationWorker()
{
}

void GComputationWorker::doWork()
{
    // Start computation
    // The progress bar is updated by setValue method
}

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Usage:

void MainWindow::startRun()
{
    ThreadManager::instance()->doComputationWork();
}
 
void MainWindow::onProgressBarValueChanged(int value)
{
    if (ui->progressBar->maximum() == value)
    {
        ui->progressBar->hide();
    }
}

void MainWindow::startRun()
{
    ThreadManager::instance()->doComputationWork();
}

void MainWindow::onProgressBarValueChanged(int value)
{
    if (ui->progressBar->maximum() == value)
    {
        ui->progressBar->hide();
    }
}

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Regards.