set progress bar values inside a thread

[ruben.rodrigues]

Hi all!

I wrote a progress bar class that has a Gui part and a thread part. In the way I have now the thread has a "for" loop that emits a signal to the Gui class and then has a 100ms sleep.

This works but the gui kinda frezzes so I was trying to implement it in another way.
I want to send the progress bar object to the thread class and set the value from there. When I tried this the programm crashed and I need some help.

here the code:

#include "progressbar.h"
 
class SleepThread : public QThread
{
public:
	static void mySleep(int nMSecs)
	{
		msleep(nMSecs);
	}
};
 
 
progressBar::progressBar(QWidget *parent)
    : QDialog(parent)
{
	ui.setupUi(this);
}
 
progressBar::~progressBar()
{
 
}
 
void progressBar::changeMessage(QString text){ //this is where I update the message from my main gui
	ui.label->setText(text);
}
 
void progressBar::init(){ //this is to open and show the progress bar
	this->show();
	pbarThread = new barThread;
	pbarThread->setProgressBar(ui.progressBar); //set the progress bar pointer
	connect(pbarThread, SIGNAL(setValue(int)), this, SLOT(setPBarValue(int)));
	pbarThread->start();
}
 
void progressBar::setPBarValue(int i){ //this is how I set the value but I don't want to use this function anymore
	ui.progressBar->setValue(i);
	if(i == 100){
		if(ui.progressBar->invertedAppearance()){
			ui.progressBar->setInvertedAppearance(false);
		}else{
			ui.progressBar->setInvertedAppearance(true);
		}
	}
}
 
void progressBar::stopPBar(){ //to stop the thread before I delete the object
	this->hide();
	pbarThread->stopThread();
	while(!pbarThread->isFinished()){
		//Wait on loop until thread is finished
	}
}
 
void barThread::stopThread(){
	running = false;
}
 
void barThread::run(){
 
	running = true;
 
	while(running){
		for(int i = 0; i < 101; i=i+5){
			_progressBar->setValue(i); //This is where it crashes now
//			emit setValue(i); //the signal I emited before to alert the Gui class
			if(!running) break;
			SleepThread::mySleep(100);
		}
	}
}

#include "progressbar.h"

class SleepThread : public QThread
{
public:
	static void mySleep(int nMSecs)
	{
		msleep(nMSecs);
	}
};


progressBar::progressBar(QWidget *parent)
    : QDialog(parent)
{
	ui.setupUi(this);
}

progressBar::~progressBar()
{

}

void progressBar::changeMessage(QString text){ //this is where I update the message from my main gui
	ui.label->setText(text);
}

void progressBar::init(){ //this is to open and show the progress bar
	this->show();
	pbarThread = new barThread;
	pbarThread->setProgressBar(ui.progressBar); //set the progress bar pointer
	connect(pbarThread, SIGNAL(setValue(int)), this, SLOT(setPBarValue(int)));
	pbarThread->start();
}

void progressBar::setPBarValue(int i){ //this is how I set the value but I don't want to use this function anymore
	ui.progressBar->setValue(i);
	if(i == 100){
		if(ui.progressBar->invertedAppearance()){
			ui.progressBar->setInvertedAppearance(false);
		}else{
			ui.progressBar->setInvertedAppearance(true);
		}
	}
}

void progressBar::stopPBar(){ //to stop the thread before I delete the object
	this->hide();
	pbarThread->stopThread();
	while(!pbarThread->isFinished()){
		//Wait on loop until thread is finished
	}
}

void barThread::stopThread(){
	running = false;
}

void barThread::run(){

	running = true;

	while(running){
		for(int i = 0; i < 101; i=i+5){
			_progressBar->setValue(i); //This is where it crashes now
//			emit setValue(i); //the signal I emited before to alert the Gui class
			if(!running) break;
			SleepThread::mySleep(100);
		}
	}
}

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#ifndef PROGRESSBAR_H
#define PROGRESSBAR_H
 
#include <QtGui>
#include "ui_progressbar.h"
#include <QtCore>
#include <qthread.h>
 
class barThread : public QThread
{
	Q_OBJECT
 
public:
    bool running;
    void stopThread();
    void setProgressBar(QProgressBar *pb){_progressBar = pb;}
 
protected:
	void run();
 
private:
	QProgressBar *_progressBar;
 
signals:
	void setValue(int);
};
 
class progressBar : public QDialog
{
    Q_OBJECT
 
public:
    progressBar(QWidget *parent = 0);
    ~progressBar();
 
    void init();
    void stopPBar();
    void changeMessage(QString);
 
private slots:
    void setPBarValue(int);
 
private:
    Ui::progressBarClass ui;
 
    barThread *pbarThread;
};
 
#endif // PROGRESSBAR_H

#ifndef PROGRESSBAR_H
#define PROGRESSBAR_H

#include <QtGui>
#include "ui_progressbar.h"
#include <QtCore>
#include <qthread.h>

class barThread : public QThread
{
	Q_OBJECT

public:
    bool running;
    void stopThread();
    void setProgressBar(QProgressBar *pb){_progressBar = pb;}

protected:
	void run();

private:
	QProgressBar *_progressBar;

signals:
	void setValue(int);
};

class progressBar : public QDialog
{
    Q_OBJECT

public:
    progressBar(QWidget *parent = 0);
    ~progressBar();

    void init();
    void stopPBar();
    void changeMessage(QString);

private slots:
    void setPBarValue(int);

private:
    Ui::progressBarClass ui;

    barThread *pbarThread;
};

#endif // PROGRESSBAR_H

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I already did once a class that showed a live picture from a thread and the method was the same.

Thanks in advance

[DanH]

1) Why do you have mySleep in a separate class? It just confuses things?

2) Why are you using sleep rather than a repetitive timer? (Then you wouldn't even need a separate thread.)

3) You should probably use Qt::QueuedConnection for the 5th parm of connect(). It should be defaulting to that, but it doesn't hurt to be specific.

[Lykurg]

All GUI stuff has to be in the main thread. Also accessing GUI parts from a custom thread is a very bad idea. So your signal/slot connection is the right thing to do. If it was freezing, then you probably called the thread function in a wrong way.