Showing progress bar while worker thread works

[olidem]

Hi!

Thanks for your replies.

But my Problem is still not solved.

I have changed my strategy a bit:
I am extensively working on a QGraphicsView and Scene, so the idea is to hide all QGraphicsItems in my scene once the computation starts, and to show a Progressbar which is a subclass of QGraphicsItem.

the code looks like that:

//MainView is derived from QGraphicsView
void MainView::loadBackgroundImage(const QString& filename)
{
	// the background item shall always be newly created.
	if(this->scene()->items().contains(this->m_background))
		this->scene()->removeItem(this->m_background);
	delete m_background;
 
	//hide all scene items
	this->m_scalable_item->setVisible(false);
 
	//get the progressbar (derived from QGraphicsItem)
	GraphicsProgressBar * g = new GraphicsProgressBar;
	this->scene()->addItem(g);
	g->setPos(this->sceneRect().center());
 
	this->scene()->update();
 
	QTimer * timer = new QTimer(this);
	connect(timer, SIGNAL(timeout()), g, SLOT(updateProgress()));
	timer->start(100);
 
	//BackgroundImageItem is derived from QObject, QThread and QGraphicsItem
	// start() starts the computation is background-thread
	m_background = new BackgroundImageItem(filename);
	m_background->start();
	qDebug() << "work started";
	//the gui thread should wait here until the worker has finished
	m_background->wait();
	qDebug() << QThread::currentThreadId() << "Waiting done.";
 
	// I just add the background item here
	this->scene()->addItem(this->m_background);
	if(!this->scene()->items().contains(m_scalable_item))
		this->scene()->addItem(m_scalable_item);
	this->m_scalable_item->setVisible(true);
 
	//free all timer resoureces and the progressbar
	timer->stop();
	timer->disconnect();
	g->disconnect();
	this->scene()->removeItem(g);
	delete g;
	delete timer;
}

//MainView is derived from QGraphicsView
void MainView::loadBackgroundImage(const QString& filename)
{
	// the background item shall always be newly created.
	if(this->scene()->items().contains(this->m_background))
		this->scene()->removeItem(this->m_background);
	delete m_background;

	//hide all scene items
	this->m_scalable_item->setVisible(false);

	//get the progressbar (derived from QGraphicsItem)
	GraphicsProgressBar * g = new GraphicsProgressBar;
	this->scene()->addItem(g);
	g->setPos(this->sceneRect().center());

	this->scene()->update();

	QTimer * timer = new QTimer(this);
	connect(timer, SIGNAL(timeout()), g, SLOT(updateProgress()));
	timer->start(100);

	//BackgroundImageItem is derived from QObject, QThread and QGraphicsItem
	// start() starts the computation is background-thread
	m_background = new BackgroundImageItem(filename);
	m_background->start();
	qDebug() << "work started";
	//the gui thread should wait here until the worker has finished
	m_background->wait();
	qDebug() << QThread::currentThreadId() << "Waiting done.";

	// I just add the background item here
	this->scene()->addItem(this->m_background);
	if(!this->scene()->items().contains(m_scalable_item))
		this->scene()->addItem(m_scalable_item);
	this->m_scalable_item->setVisible(true);

	//free all timer resoureces and the progressbar
	timer->stop();
	timer->disconnect();
	g->disconnect();
	this->scene()->removeItem(g);
	delete g;
	delete timer;
}

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The Progressbar code looks like:

class GraphicsProgressBar : public QObject,  public QGraphicsItem
{
	Q_OBJECT
 
public:
 
	GraphicsProgressBar()
	{
		setZValue(5);
		status = 1;
	};
 
	inline QRectF boundingRect() const { return QRectF(-66,-21,132,42); };
 
	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
	{
		qDebug() << "paint";
		painter->drawRect(-66,-21,132,42);
		if(status >=1)
			painter->drawRect(-65,-20,40,40);
		if(status >=2)
			painter->drawRect(-20,-20,40,40);
		if(status >=3)
			painter->drawRect(25,-20,40,40);
	};
 
public slots:
 
	void updateProgress()
	{
		status = (status+1)%4;
		qDebug() << QThread::currentThreadId() << status;
		//this->update();
	};
 
 
private:
	int status;
};

class GraphicsProgressBar : public QObject,  public QGraphicsItem
{
	Q_OBJECT

public:

	GraphicsProgressBar()
	{
		setZValue(5);
		status = 1;
	};

	inline QRectF boundingRect() const { return QRectF(-66,-21,132,42); };

	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
	{
		qDebug() << "paint";
		painter->drawRect(-66,-21,132,42);
		if(status >=1)
			painter->drawRect(-65,-20,40,40);
		if(status >=2)
			painter->drawRect(-20,-20,40,40);
		if(status >=3)
			painter->drawRect(25,-20,40,40);
	};

public slots:

	void updateProgress()
	{
		status = (status+1)%4;
		qDebug() << QThread::currentThreadId() << status;
		//this->update();
	};


private:
	int status;
};

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The progressbar does not show up.
Also, the hiding
The paint method gets never called!
Also the debugmsg from updateProgress never appears.
It seems that nothing I try to change at the graphicsScene or view has an effect.
Its not even possible to hide all elements.

HELP appreciated!

[nix]

Hi,

I think your problem comes from following line :

//the gui thread should wait here until the worker has finished
m_background->wait();

//the gui thread should wait here until the worker has finished
m_background->wait();

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It seems you want block the Gui thread during the processing. But how your progressbar should be managed and refreshed if the GUI thread is blocked ??

You don't have to block the GUI thread, use QThread::finished() signal for manage post-treatement & cleaning once the processing is completed.

'hope it will help you.

[olidem]

Hi,

I think your problem comes from following line :

//the gui thread should wait here until the worker has finished
m_background->wait();

//the gui thread should wait here until the worker has finished
m_background->wait();

To copy to clipboard, switch view to plain text mode 

It seems you want block the Gui thread during the processing. But how your progressbar should be managed and refreshed if the GUI thread is blocked ??

You don't have to block the GUI thread, use QThread::finished() signal for manage post-treatement & cleaning once the processing is completed.

'hope it will help you.

Yes!
That was the hint I needed!
Thanks a lot!