QList<QPixmap> 'index out of range'
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I'm trying to make a list of pixmaps for a program I'm writing, but when I try to get something from the list, I get this error:
ASSERT failure in QList<T>::at: "index out of range", file ........\QtSDK\Desktop\Qt\4.7.3\mingw\include/QtCore/qlist.h, line 456
Invalid parameter passed to C runtime function.
Invalid parameter passed to C runtime function.When I went into Qt Creator's debug mode, I found that the list of pixmaps wasn't being populated at all. I think I need to create a new QList<Pixmap> in the MainWindow constructor (with 'thumbnailPixmapList = new QList<QPixmap>();'), but the compiler gives me this error:
error: no match for 'operator=' in '((MainWindow*)this)->MainWindow::thumbnailPixmapList = (operator new(4u), (<statement>, ((QList<QPixmap>*)<anonymous>)))'
This is the function I'm using to populate the list:
@void MainWindow::createThumbnailPixmaps()
{
for (int i=0; i<thumbnailPixmapList.size(); ++i)
{
QPixmap thumbnailPix(QPixmap::fromImage(extractSlice(0,i)));
thumbnailPixmapList.insert(i, thumbnailPix);
}
}@This is one of the functions I want to use to get a list item:
@void MainWindow::forwardSlice()
{
QPixmap nextPix = thumbnailPixmapList.at(s+1);
s+=1;
ui->horizontalSlider->setValue(s);
newSlice2->setPixmap(nextPix);
ui->sliceView->update();
}@Please let me know if there's anything I'm doing wrong.
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[quote author="jesbb" date="1309186814"]
@void MainWindow::forwardSlice()
{
QPixmap nextPix = thumbnailPixmapList.at(s+1);
s+=1;
ui->horizontalSlider->setValue(s);
newSlice2->setPixmap(nextPix);
ui->sliceView->update();
}@[/quote]
That part does not look safe at all.
What is the contents of "s" ? You might want to make sure that it is within the bounds 0 <= s < thumbnailPixmapList.size(). -
[quote author="jesbb" date="1309186814"]
@void MainWindow::createThumbnailPixmaps()
{
for (int i=0; i<thumbnailPixmapList.size(); ++i)
{
QPixmap thumbnailPix(QPixmap::fromImage(extractSlice(0,i)));
thumbnailPixmapList.insert(i, thumbnailPix);
}
}@
[/quote]Was a little fast in answering. Here is another problem. How do you want to loop if nothing is in the list?
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's' is an integer; its default value is 50. If I wanted to make sure if 0 <= s < thumbnailPixmapList.size(), would I need to make an if loop to put inside the forwardSlice method?
I haven't thought about how I would loop if nothing is in the list.
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I do not know where you are getting the parts of your picture, but all looks a little suspicious to me.
Assuming that somehow extractSlice (0, j) makes sense for j up to 9. This would make more sense.
@void MainWindow::createThumbnailPixmaps()
{
for (int j=0; j < 10; ++j)
{
QPixmap thumbnailPix(QPixmap::fromImage(extractSlice(0,j)));
thumbnailPixmapList.push_back (thumbnailPix);
}
}@For reading you could use something similar to:
@void MainWindow::forwardSlice()
{
if ( s >= 0 && s < thumbnailPixmapList.size() )
{
QPixmap nextPix = thumbnailPixmapList.at(s);
++s;
ui->horizontalSlider->setValue(s);
newSlice2->setPixmap(nextPix);
ui->sliceView->update();
}
}@Disclaimer: This part of code is typed directly into the thread. Furthermore, I cannot know what you are up to. So, the snippet might need significant additions until it runs as you need.
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I made some minor changes to the code you gave me and it works now.
Thank you very much for your help; I really appreciate it!
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To see what triggers this type of error you should run it in qt-creator in the debugger then click on each higher function in the call stack and inspect the local variables to see what causes the problem.