I imitated Image Viewer example but...

[sincnarf]

I exactly copied all the stuff from the Image Viewer example of Qt, except for the constructor. I modified it the constructor so it would auto load an image coming from another mainwindow that calls

ImageViewer imageViewer(&image);

ImageViewer imageViewer(&image);

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Now I am having trouble with the class because it closes/quits... and I am sure that that class's method show() ( opens for x milliseconds then closes).

I've read this
http://www.qtcentre.org/forum/f-qt-p...t=QApplication
and it says two QApplication can't run at the same time. So how am I going to let the ImageViewer window stay (not instantly quit on show()). ? Because as of now I can't manually close it.. it closes on itself?

Here goes the modified constructor of ImageViewer.

ImageViewer::ImageViewer(const QImage *image) {
	imageLabel = new QLabel;
	imageLabel->setBackgroundRole(QPalette::Base);
	imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
	imageLabel->setScaledContents(true);
 
	scrollArea = new QScrollArea;
	scrollArea->setBackgroundRole(QPalette::Dark);
	scrollArea->setWidget(imageLabel);
	setCentralWidget(scrollArea);
 
	createActions();
	createMenus();
 
	setWindowTitle(tr("Image Viewer"));
	resize(500, 400);
 
// this is where the opening of the passed const image starts
 
	if (image->isNull() || image == 0) {
		QMessageBox::information(this, tr("Image Viewer"),
				tr("Cannot load the image."));
		return;
	}
 
	QPixmap pixmap = QPixmap::fromImage(*image);
 
	imageLabel->setPixmap(pixmap);
	scaleFactor = 1.0;
 
	printAct->setEnabled(true);
	fitToWindowAct->setEnabled(true);
	updateActions();
 
	if (!fitToWindowAct->isChecked())
		imageLabel->adjustSize();
 
// suddenly closes ! ! !
	show();
}

ImageViewer::ImageViewer(const QImage *image) {
	imageLabel = new QLabel;
	imageLabel->setBackgroundRole(QPalette::Base);
	imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
	imageLabel->setScaledContents(true);

	scrollArea = new QScrollArea;
	scrollArea->setBackgroundRole(QPalette::Dark);
	scrollArea->setWidget(imageLabel);
	setCentralWidget(scrollArea);

	createActions();
	createMenus();

	setWindowTitle(tr("Image Viewer"));
	resize(500, 400);
	
// this is where the opening of the passed const image starts

	if (image->isNull() || image == 0) {
		QMessageBox::information(this, tr("Image Viewer"),
				tr("Cannot load the image."));
		return;
	}

	QPixmap pixmap = QPixmap::fromImage(*image);

	imageLabel->setPixmap(pixmap);
	scaleFactor = 1.0;

	printAct->setEnabled(true);
	fitToWindowAct->setEnabled(true);
	updateActions();

	if (!fitToWindowAct->isChecked())
		imageLabel->adjustSize();

// suddenly closes ! ! !
	show();
}

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I've also read http://www.qtcentre.org/forum/f-qt-p...ght=maptoscene so. how do I NOT destroy the ImageViewer after calling its constructor?

[marcel]

Oh, now I get it.
You were creating the image viewer on the stack:

ImageViewer imageViewer(&image);

ImageViewer imageViewer(&image);

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Create it on the heap, so it won't be destroyed as soon as the scope in which you created it ends:

ImageViewer *imageViewer = new ImageViewer(&image);

ImageViewer *imageViewer = new ImageViewer(&image);

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Or make it a class member.

[sincnarf]

that was fast.. So basic... I'm really sorry. Getting pressured here. Thanks again

[bpetty]

This may come over as nitpicking but in my opinion you are doing too much logic in your constructor... from a software engineering standpoint. I *try* to write my constructors such that they only initialize member variables. If I need more than that I will usually write an Init() method. Your case is a little different... modulizing it might be a good start.