Crash while calling setItemWidget - c++

Question

I am using a QTreeWidget and setting a widget for the QTreeWidgetItem in the QTreeWidget. It is working fine but when I do the same for second time, the application is crashing.
The below is working fine.
QTreeWidget* treewidget = new QTreeWidget();
QTreeWidgetItem* item0 = new QTreeWidgetItem((QTreeWidget*)0, QStringList(QString("item0")));
treewidget->insertTopLevelItem(0,item0);
QSlider* slider0 = new QSlider();
treewidget->setItemWidget(item0, 0, slider0);
But if I add the last line once again, it is crashing when running the application.
The below is crashing.
QTreeWidget* treewidget = new QTreeWidget();
QTreeWidgetItem* item0 = new QTreeWidgetItem((QTreeWidget*)0, QStringList(QString("item0")));
treewidget->insertTopLevelItem(0,item0);
QSlider* slider0 = new QSlider();
treewidget->setItemWidget(item0, 0, slider0);
treewidget->setItemWidget(item0, 0, slider0); // Intentionally added to simulate the issue
The above is an example to show the issue, but in my application, based on some events, I delete the tree widget items and add it later. When I set the item widget (after adding the items later), I am getting the crash.
I could not figure out why. Any ideas? FYI, I am using Qt 5.3.2 MSVC 2010, 32 bit.

Answer 1

treewidget->setItemWidget(item0, 0, slider0);
treewidget->setItemWidget(item0, 0, slider0);// Intentionally added to simulate the issue
I look at Qt code (4.x):
void QTreeWidget::setItemWidget(QTreeWidgetItem *item, int column, QWidget *widget)
{
Q_D(QTreeWidget);
QAbstractItemView::setIndexWidget(d->index(item, column), widget);
}
and QAbstractItemView::setIndexWidget:
void QAbstractItemView::setIndexWidget(const QModelIndex &index, QWidget *widget)
{
Q_D(QAbstractItemView);
if (!d->isIndexValid(index))
return;
if (QWidget *oldWidget = indexWidget(index)) {
d->persistent.remove(oldWidget);
d->removeEditor(oldWidget);
oldWidget->deleteLater();
}
so if you add slider0 two times, then at first call it was added,
at seconds call Qt call for it deleteLater, and then added it,
are sure that this is what you want?

Answer 2

You have to set correct parent in the constructor of QTreeWidgetItem. Try this:
QTreeWidgetItem* item0 = new QTreeWidgetItem(treewidget);
Also it is important to understand who is owner of the slider0 after calling of setItemWidget(): the owner is your table, so 1) you don't need to delete this object; 2) the object will be deleted if you call setItemWidget for the same cell again. So, double call of treewidget->setItemWidget(item0, 0, slider0); seems very strange (second time you are setting the deleted object into that cell).