QGraphicsView class crashes the application

venkatesh

Its initialised at the header in ImageRegistrationImplementation.h

@

private:

listWidget listObject_;
StationaryImageViewer StationaryImageObject_;
MovingImageViewer MovingImageObject_;

@

venkatesh

I could understand the program crashes at the line

@

QVariant StationaryImageData_=StationaryImageQListItem_->data(Qt::UserRole);

@

But i don't know why

SGaist

Hi,

Are you sure StationaryImageQListItem_ is valid ?

venkatesh

Hi,
I have used an object created from a class listWidget

@
listWidget listWidgetViewerObject;
@

to get the current item of the listWidget using

@

StationaryImageQListItem_ =listWidgetViewerObject.currentItem();

@

and used it in QVariant. I don't understand what's going wrong here

SGaist

Again, are you sure that StationaryImageQListItem_ is pointing to a valid item ?

venkatesh

I tried to reimplement it in another way as

listWidget.cpp

@

QString listWidget::ConvertMovingData_()
{
QVariant MovingImageData_=item(currentRow()+1)->data(Qt::UserRole);
QString MovingData_=MovingImageData_.toString();
QFileInfo MovingImageInfo_(MovingData_);
QString MovingImageFilePath_= MovingImageInfo_.absoluteFilePath();
return MovingImageFilePath_;

}

QString listWidget::ConvertStationaryData_()
{
QVariant StationaryImageData_=currentItem()->data(Qt::UserRole);
QString StationaryData_=StationaryImageData_.toString();
QFileInfo StationaryImageInfo_(StationaryData_);
QString StationaryImageFilePath_= StationaryImageInfo_.absoluteFilePath();
return StationaryImageFilePath_;

}

@

listWidget.h

@
public slots:
QString ConvertMovingData_();
QString ConvertStationaryData_();
@

And i used it in

movingimageviewer.cpp

@

void MovingImageViewer::setMovingImage_()
{
MovingImageScene_->removeItem(MovingImageViewItem_);
MovingImageScene_->clear();
QString MovingStringData=listWidgetMovingViewerObject.ConvertMovingData_();
MovingImagePixmap_.load(MovingStringData);
MovingImageViewItem_->setPixmap(MovingImagePixmap_);
MovingImageScene_->addItem(MovingImageViewItem_);
fitInView(MovingImageScene_->itemsBoundingRect(),Qt::IgnoreAspectRatio);
setScene(MovingImageScene_);
show();
update();
}
@

similarly in

@

void StationaryImageViewer::setStationaryImage_()
{

StationaryImageScene_->removeItem(StationaryImageViewItem_);
StationaryImageScene_->clear();
QString StationaryStringData= listWidgetStationaryObject.ConvertStationaryData_();
StationaryImagePixmap_.load(StationaryStringData);
StationaryImageViewItem_->setPixmap(StationaryImagePixmap_);
StationaryImageScene_->addItem(StationaryImageViewItem_);
fitInView(StationaryImageScene_->itemsBoundingRect(),Qt::IgnoreAspectRatio);
setScene(StationaryImageScene_);
show();
update();

}

@

venkatesh

This is the crash report for this implementation

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 com.yourcompany.ImageRegistration 0x0000000100055d4f listWidget::ConvertStationaryData_() + 31 (listWidget.cpp:58)
1 com.yourcompany.ImageRegistration 0x0000000100056a44 StationaryImageViewer::setStationaryImage_() + 68 (stationaryimageviewer.cpp:21)

which again corresponds to the @QVariant@ implementation

SGaist

You still don't check whether the return value of currentItem() is valid

venkatesh

Hi,

How can I check whether it is valid ?? I thought it should be valid, as I am just taking the data of the item which is clicked in listWidget. Is there a way to check In Qt, like catching an exception ? Or error

SGaist

Just test if the pointer is null