[英]Qt QAbstractItemModel - item removal crashes
我正在使用Qt類編寫應用程序,我有一個層次結構,我需要在樹視圖中顯示它(我使用的是QTreeView小部件)。 數據本身如下所示:
class StatisticsEntry
{
// additional data management methods
...
bool setData(int column, const QVariant &value)
{
if (column < 0 || column >= _data.size())
return false;
_data[column] = value;
return true;
}
private:
// each item has a parent item except the top-most one
StatisticsEntry *_parent;
// each item may have child items which are accessible through the following member
QList<StatisticsEntry*> _children;
// each item is defined by a set of vallues stored in the following vector
QVector<QVariant> _data;
}
我有一個名為StatisticsModel的類,它實現了QAbstractItemModel - 用它來操作和呈現存儲在StatisticsEntry樹中的數據。 該類有一個名為addStatisticsData的方法,我用它將StatisticsEntry記錄推送到模型中。 該方法大致如下所示:
QModelIndex StatisticsModel::addStatisticsData(const QString &title, const QString &description, const QModelIndex &parent)
{
int row = rowCount(parent);
if (!insertRow(row, parent))
return QModelIndex();
// Get new item index
QModelIndex child = index(row, 0, parent);
// set item data
setTitle(child, title);
setDescription(child, description);
return child;
}
SetTitle和setDescription方法是相同的 - 這是setTitle一個:
void StatisticsModel::setTitle(const QModelIndex &index, const QString& title)
{
QModelIndex columnIndex = this->index(index.row(), StatColumn::Title, index.parent());
this->setData(columnIndex, title, Qt::EditRole);
}
setData方法如下:
bool StatisticsModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
if (role != Qt::EditRole)
return false;
int column = index.column();
StatisticsEntry *item = getItem(index);
if (!item->setData(column, value))
return false;
emit dataChanged(index, index);
return true;
}
剩下的是getItem方法:
StatisticsEntry *StatisticsModel::getItem(const QModelIndex &index) const
{
if (index.isValid())
{
StatisticsEntry *item = static_cast<StatisticsEntry*>(index.internalPointer());
if (item)
return item;
}
return _rootItem;
}
這是關於添加新的和修改現有條目的所有內容。 在我的應用程序中,我也實現了QSortFilterProxyModel - 沒有什么特別的,只有lessThan方法。 我使用代理模型在QTreeView中提供顯示數據的排序功能。 有以下代碼將模型連接到treeview小部件:
在主窗口的標題中:
...
StatisticsModel* _statisticsModel;
StatisticsProxyModel* _statisticsProxyModel;
...
在主寡婦的構造函數中
...
_statisticsModel = new StatisticsModel(ths);
_statisticsProxyModel = new StatisticsProxyModel(htis);
...
_statisticsProxyModel->setSourceModel(_statisticsModel);
ui->statisticsTreeView->setModel(_statisticsProxyModel);
...
該應用程序還有一個按鈕,允許我從模型中刪除所選項目 - 我目前只測試QTreeView :: selectionModel() - > currentIndex,暫時沒有多項選擇。
我有StatisticsModel :: removeRows方法的以下代碼
bool StatisticsModel::removeRows(int position, int rows, const QModelIndex &parent)
{
StatisticsEntry *parentItem = getItem(parent);
bool success1 = true;
bool success2 = true;
beginRemoveRows(parent, position, position + rows - 1);
for (int i = position + rows - 1; i >= position; i--)
{
QModelIndex child = index(i, 0, parent);
QString title = this->title(child); // the title method is the getter method that matches the setTitle one
success1 = success1 && removeRows(0, rowCount(child), child); //rowCount is implemented to return the number of items stored in StatisticsEntry::_children list for the specified parent index
success2 = success2 && parentItem->removeChild(i); // deletes an entry from the StatisticsEntry::_children list
}
endRemoveRows();
return success1 && success2;
}
問題是,有時當我使用QAbstractItemModel :: removeRow方法刪除項目時,我得到一個異常,堆棧跟蹤如下所示:
StatisticsModel::parent StatisticsModel.cpp 307 0x13e7bf8
QModelIndex::parent qabstractitemmodel.h 393 0x72e57265
QSortFilterProxyModelPrivate::source_to_proxy qsortfilterproxymodel.cpp 386 0x711963e2
QSortFilterProxyModel::mapFromSource qsortfilterproxymodel.cpp 2514 0x7119d28b
QSortFilterProxyModel::parent qsortfilterproxymodel.cpp 1660 0x7119a32c
QModelIndex::parent qabstractitemmodel.h 393 0x72e57265
QPersistentModelIndex::parent qabstractitemmodel.cpp 347 0x72e58b86
QItemSelectionRange::isValid qitemselectionmodel.h 132 0x70e3f62b
QItemSelection::merge qitemselectionmodel.cpp 466 0x711503d1
QItemSelectionModelPrivate::finalize qitemselectionmodel_p.h 92 0x7115809a
QItemSelectionModelPrivate::_q_rowsAboutToBeRemoved qitemselectionmodel.cpp 623 0x71151132
QItemSelectionModel::qt_static_metacall moc_qitemselectionmodel.cpp 113 0x711561c2
QMetaObject::activate qobject.cpp 3547 0x72e8d9a4
QAbstractItemModel::rowsAboutToBeRemoved moc_qabstractitemmodel.cpp 204 0x72f08a76
QAbstractItemModel::beginRemoveRows qabstractitemmodel.cpp 2471 0x72e5c53f
QSortFilterProxyModelPrivate::remove_proxy_interval qsortfilterproxymodel.cpp 558 0x71196ce7
QSortFilterProxyModelPrivate::remove_source_items qsortfilterproxymodel.cpp 540 0x71196c7f
QSortFilterProxyModelPrivate::source_items_about_to_be_removed qsortfilterproxymodel.cpp 841 0x71197c77
QSortFilterProxyModelPrivate::_q_sourceRowsAboutToBeRemoved qsortfilterproxymodel.cpp 1291 0x711995cc
QSortFilterProxyModel::qt_static_metacall moc_qsortfilterproxymodel.cpp 115 0x7119d506
QMetaCallEvent::placeMetaCall qobject.cpp 525 0x72e883fd
QObject::event qobject.cpp 1195 0x72e894ba
QApplicationPrivate::notify_helper qapplication.cpp 4550 0x709d710e
QApplication::notify qapplication.cpp 3932 0x709d4d87
QCoreApplication::notifyInternal qcoreapplication.cpp 876 0x72e6b091
奇怪的是,在關於物品移除的所有即時方法調用已經結束之后,這似乎發生了。 似乎代理模型正在尋找不再存在的模型索引(或者我認為)。 StatisticsModel :: parent方法如下:
QModelIndex StatisticsModel::parent(const QModelIndex &index) const
{
if (!index.isValid())
return QModelIndex();
StatisticsEntry *childItem = getItem(index);
StatisticsEntry *parentItem = childItem->parent();
if (NULL != parentItem)
return createIndex(parentItem->childNumber(), 0, parentItem);
return QModelIndex();
}
當異常發生時,與上述方法中的childItem和parentItem變量關聯的值似乎無效 - 指針本身指向不可訪問的內存,或者成員QLists沒有條目或其條目給出內存訪問沖突。 可能是父方法不正確,但后來如何獲取父索引 - qabstractItemModel文檔不鼓勵在該方法中使用QModelIndex :: parent,因為它將創建無限遞歸。
任何幫助,將不勝感激,
在執行StatisticsModel::removeRows
,您正在嵌套begingRemoveRows/endRemoveRows
,這些AFAIK不起作用。 你應該做:
bool StatisticsModel::removeRows(int position, int rows, const QModelIndex &parent)
{
StatisticsEntry *parentItem = getItem(parent);
bool success1 = true;
bool success2 = true;
for (int i = position + rows - 1; i >= position; i--)
{
QModelIndex child = index(i, 0, parent);
QString title = this->title(child); // the title method is the getter method that matches the setTitle one
success1 = success1 && removeRows(0, rowCount(child), child); //rowCount is implemented to return the number of items stored in StatisticsEntry::_children list for the specified parent index
beginRemoveRows(parent, i, i);
success2 = success2 && parentItem->removeChild(i); // deletes an entry from the StatisticsEntry::_children list
endRemoveRows();
}
return success1 && success2;
}
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