I want to create same kind of QTreeView (not QTreeWidget) structure as shown in attached figure.. This is Property Editor of QT.
I am using QT-4.6
On 2nd column, depending on different condition, I can have either a spin box, or a drop down or a checkbox or text edit... and so on...
Please guide me on how to set different delegates in different cells of a particular column.
From docs, it is evident that there is no straight away API for setting delegate on a cell (rather is available for full widget or a row or a column).
All QAbstractItemDelegate methods, like createEditor or paint, have a model index as one of their parameters. You can access model data using that index and create an appropriate delegate widget. When you create your model you should set some value to every item that will be used to distinguish its type.
An example:
enum DelegateType
{
DT_Text,
DT_Checkbox,
DT_Combo
}
const int MyTypeRole = Qt::UserRole + 1;
QStandardItemModel* createModel()
{
QStandardItemModel *model = new QStandardItemModel;
QStandardItem *item = new QStandardItem;
item->setText("Hello!");
item->setData(DT_Checkbox, MyTypeRole);
model->appendRow(item);
return model;
}
QWidget* MyDelegate::createEditor(QWidget *parent,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
int type = index.data(MyTypeRole).toInt();
// this is a simplified example
switch (type)
{
case DT_Text:
return new QLinedEdit;
case DT_Checkbox:
return new QCheckBox;
case DT_Combo:
return new QComboBox;
default:
return QItemDelegate::createEditor(parent, option, index);
}
}
#hank This is in response to your last comment... Do you see any flaw in it ?
MyItem* item2 = new MyItem(second);
item2->setData(delType, **MyTypeRole**);
if(delType == DT_Combo)
{
QString str1, str2, str3;
QStringList abc ;
abc << ("1" + str1.setNum(counter) ) << ("2" + str2.setNum(counter) )<< ( "3" + str3.setNum(counter) );
item2->setData(abc, MyTypeRole1);
}
QWidget* MyDelegate::createEditor(QWidget *parent,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
int type = index.data(MyTypeRole).toInt();
// this is a simplified example
switch (type)
{
case DT_Text:
return new QLinedEdit;
case DT_Combo:
{
QComboBox* cb = new QComboBox(parent);
QStringList entries - index.data(MyTypeRole1).toStringList();
cb->addItems(entries)
return cb;
}
On different item2, I dynamically create entries with a counter variable that is different everytime it comes here...
Here, different combo boxes display different entries.
Does the approach looks fine to you ?
I've created a QAbstractListModel derived model based on an underlying QHash. Since I need to use the model in QML, I cannot make use of the sorting functionality Qt widgets and views have integrated.
I tried using a QSortFilterProxyModel but it doesn't seem to work with my model. Getting the model to properly work in QML wasn't tedious enough, and now I am stuck on sorting.
Any suggestions are appreciated.
Here is the model source:
typedef QHash<QString, uint> Data;
class NewModel : public QAbstractListModel {
Q_OBJECT
Q_PROPERTY(int count READ count NOTIFY countChanged)
public:
NewModel(QObject * parent = 0) : QAbstractListModel(parent) {}
enum Roles {WordRole = Qt::UserRole, CountRole};
QHash<int, QByteArray> roleNames() const {
QHash<int, QByteArray> roles;
roles[WordRole] = "word";
roles[CountRole] = "count";
return roles;
}
QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const {
if (index.row() < 0 || index.row() >= m_data.size()) return QVariant();
Data::const_iterator iter = m_data.constBegin() + index.row();
switch (role) {
case WordRole:
return iter.key();
case CountRole:
return iter.value();
} return QVariant();
}
int rowCount(const QModelIndex &parent) const {
Q_UNUSED(parent)
return m_data.size();
}
int count() const { return m_data.size(); }
public slots:
void append(const QString &word) {
bool alreadyThere = m_data.contains(word);
if (alreadyThere) m_data[word]++;
else m_data.insert(word, 1);
Data::const_iterator iter = m_data.find(word);
uint position = delta(iter);
if (alreadyThere) {
QModelIndex index = createIndex(position, 0);
emit dataChanged(index, index);
} else {
beginInsertRows(QModelIndex(), position, position);
endInsertRows();
emit countChanged();
}
}
void prepend(const QString &word) {
if (m_data.contains(word)) m_data[word]++;
else m_data.insert(word, 1);
}
signals:
void countChanged();
private:
uint delta(Data::const_iterator i) {
uint d = 0;
while (i != m_data.constBegin()) { ++d; --i; }
return d;
}
Data m_data;
};
Here is "trying" to sort it:
NewModel model;
QAbstractItemModel * pm = qobject_cast<QAbstractItemModel *>(&model);
QSortFilterProxyModel proxy;
proxy.setSourceModel(pm);
proxy.setSortRole(NewModel::WordRole);
proxy.setDynamicSortFilter(true);
Alas, the proxy works as a model, but it doesn't sort the entries.
If you enable QSortFilterProxyModel::setDynamicSortFilter(true), you need to call QSortFilterProxyModel::sort(...) function once to let the proxy know which way to sort.
With that, any time the model is updated the proxy will sort everything again just automatically.
proxy.setDynamicSortFilter(true);
proxy.sort(0);
First of all, There's no need for qobject_cast<QAbstractItemModel *> downcasting -- the NewModel is a derived class of the QAbstractItemModel and the polymorphism principle says that you can use a subclass everywhere where a parent class is applicable.
Second, your prepend method does not use beginInsertRows and endInsertRows. That's a violation of the MVC API. You'll get data corruption in the attached views and proxy models if you use it this way.
Third, you haven't mentioned whether you're actually using your proxy model as the model for the attached view :).
Finally, you are using QHash as a backing store of your data with QHash::iterator for insertion. That's an itneresting solution, but something which just cannot work -- an insertion or removal can cause the hash table to grow/shrink, which means changing all data you publish via your model indexes. This is just not going to work. Don't use QHash when you need a stable order. The O(n) complexity of your delta method should be interpreted as a warning; this is a wrong approach.
Have a Look at https://github.com/oKcerG/SortFilterProxyModel. This project exposes the functionality of QSortFilterProxyModel nicely to QML. I used it in different projects and it junst worked. However if you want to implement your own solution it's something to get your ideas.
I have a matrix of data, I simply stored it as a QList of QStringLists, all containing an equal number of QStrings. In this way, the data looks almost like a spreadsheet.
I use a QTableView to present this data to the user:
void DialogwitQTableView::setData(QList<QStringList> s)
{
/* Create the data model */
// 1. give it some headers
QStandardItemModel model = new QStandardItemModel(s.count(),25,this); //x Rows and 25 Columns
model->setHorizontalHeaderItem(0, new QStandardItem(QString("Column 1")));
model->setHorizontalHeaderItem(1, new QStandardItem(QString("Column 2")));
// ...
model->setHorizontalHeaderItem(24, new QStandardItem(QString("Column 25")));
// 2. populate the model with the data
for(int i = 0; i < s.count() ; i++)
{
for(int j = 0; j < s[i].count() ; j++)
model->setItem(i,j,new QStandardItem(QString(s[i][j])));
}
ui->NameOfTheTableView->setModel(model);
}
Now, if the user wants to change some of the data, he will just doubleclick in the QTableView in the Dialogbox and edits what he wants.
How do I get that edit also in the data? How can I adapt the QStringList with that new information?
If I search for documentation, I mostly find QTableViews linked to databases, but I don't see how this will work with a simple datastructure in memory. If I go to QtDesigner and click on "go to slots" for the TableView, I also do not see a slot called "datachanged" or anything similar.
Any thoughts? I feel pretty stuck and I am probably overviewing something, any tip is very welcome.
Looking at the doco, a QTableView inherits 6 signals from QAbstractItemView
http://doc.qt.digia.com/qt/qabstractitemview.html#signals
This class has all sorts of functionality for capturing edits, and edit triggers.
Once you can catch when the data is changed you can recommit it back to your model if you are using an MVC view. I am sure there are a lot of examples.
Hope that helps.
I think that for more complicated cases it's always best to use the abstract classes, more specifically QAbstractTableModel in this case.
Looking at this file, I just replaced Contact with StringList and changed the getters and setters. Check it out:
https://doc.qt.io/qt-5/qtwidgets-itemviews-addressbook-tablemodel-cpp.html
TableModel::TableModel(QObject *parent) :
QAbstractTableModel(parent)
{
}
TableModel::TableModel(QList<QStringList> stringLists, QObject *parent) :
QAbstractTableModel(parent),
stringLists(stringLists)
{
}
int TableModel::rowCount(const QModelIndex &parent) const
{
Q_UNUSED(parent);
return stringLists.size();
}
int TableModel::columnCount(const QModelIndex &parent) const
{
Q_UNUSED(parent);
return 2; // put the amount of columns here
}
QVariant TableModel::data(const QModelIndex &index, int role) const
{
if (!index.isValid()) return QVariant();
if (index.row() >= stringLists.size() || index.row() < 0) return QVariant();
if (role == Qt::DisplayRole) {
const auto &strings = stringLists.at(index.row());
if (index.column() == 0)
return strings[0];
else if (index.column() == 1)
return strings[1];
}
return QVariant();
}
QVariant TableModel::headerData(int section, Qt::Orientation orientation, int role) const
{
if (role != Qt::DisplayRole)
return QVariant();
if (orientation == Qt::Horizontal) {
switch (section) {
case 0:
return tr("String 1");
case 1:
return tr("String 2");
default:
return QVariant();
}
}
return QVariant();
}
bool TableModel::insertRows(int position, int rows, const QModelIndex &index)
{
Q_UNUSED(index);
beginInsertRows(QModelIndex(), position, position + rows - 1);
for (int row = 0; row < rows; ++row)
stringLists.insert(position, { QString(), QString() });
endInsertRows();
return true;
}
bool TableModel::removeRows(int position, int rows, const QModelIndex &index)
{
Q_UNUSED(index);
beginRemoveRows(QModelIndex(), position, position + rows - 1);
for (int row = 0; row < rows; ++row)
stringLists.removeAt(position);
endRemoveRows();
return true;
}
bool TableModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
if (index.isValid() && role == Qt::EditRole) {
int row = index.row();
auto strings = stringLists.at(row);
if (index.column() == 0)
strings[0] = value.toString();
else if (index.column() == 1)
contact[1] = value.toString();
else
return false;
stringLists.replace(row, contact);
emit dataChanged(index, index, {role});
return true;
}
return false;
}
Qt::ItemFlags TableModel::flags(const QModelIndex &index) const
{
if (!index.isValid()) return Qt::ItemIsEnabled;
return QAbstractTableModel::flags(index) | Qt::ItemIsEditable;
}
QList<QStringList> TableModel::getStringLists() const
{
return stringLists;
}
I also highly recommend that you read this:
https://doc.qt.io/qt-5/modelview.html
Hope it helps.
If I search for documentation, I mostly find QTableViews linked to
databases, but I don't see how this will work with a simple
datastructure in memory.
QTableView is a part of Qt's Model/View framework. There are bunch of examples of model-views.
How do I get that edit also in the data? How can I adapt the
QStringList with that new information?
At least these solutions exists:
You can grab all data from QStandardItemModel via item method.
Connect to QStandardItemModel::itemChanged signal.
You can make your own model via subclassing (and I suggest to base on QAbstractTableModel) and implement several methods (data, setData + several utility methods).
I am using QFileSystemModel to represent file structure through the QTreView. Everything works fine, but I need to add an additional row at some level of the tree. For example for now is:
-root
--row1
--row2
--row3
All these rows mapping folders/files from file system.
I need:
-root
--row1
--row2
--row3
--custom row
So custom row is not representing any data from file system. I just need to add here my own data.
I have read a lot of stuff from the internet and people advice to use proxy model and reimplement rowCount(), data() and flags() functions. I tried to do that(used class derived from QSortFilterProxyModel), but I never get my row in data() and flags() functions. Seems like it takes count from source model.
QVariant AddonFilterModel::data (const QModelIndex & index, int role) const
{
if(role == Qt::DisplayRole && index.row() == FilterModel::rowCount(index))
{
return QString("Add-Ons");
}
return FilterModel::data(index, role);
}
Qt::ItemFlags AddonFilterModel::flags(const QModelIndex & index) const
{
if (!index.isValid())
return 0;
if (index.row() == FilterModel::rowCount(index))
{
return Qt::ItemIsEnabled | Qt::ItemIsSelectable;
}
return FilterModel::flags(index);
}
int AddonFilterModel::rowCount(const QModelIndex &parent) const
{
int count = FilterModel::rowCount(parent);
if(parent == this->getRootIndex())
{
return count+1;
}
return count;
}
Using class derived from QAbstractProxyModel is not acceptable because I need filtering functions of QSortFilterProxyModel().
Also I have tried to reimplement rowCount() of QFileSystemModel to make changes directly in model but I am getting "array out of range" error from QT code.
I have tried insertRow() method but it is not working. I think because QFileSystemModel is read only.
Did anyone face this problem? Any ideas?
Late answer. You have to subclass Qabstractitemmodel.
What I have:
QTreeView class with table data
And connected QAbstractTableModel model
Question: how to save expanded state of items? Is some one have finished solutions?
PS: I know, that I can do this code by myself, but I don't have much time, and this is not the major problem of our project, but still we need it, because app contain a lot of such tables, and every time expanding tree items is annoyed process...
First, thanks to Razi for persistentIndexList and isExpanded way.
Second, here is the code which works for me just fine :-)
dialog.h file:
class Dialog : public QDialog
{
Q_OBJECT;
TreeModel *model;
TreeView *view;
public:
Dialog(QWidget *parent = 0);
~Dialog(void);
void reload(void);
protected:
void createGUI(void);
void closeEvent(QCloseEvent *);
void saveState(void);
void restoreState(void);
};
dialog.cpp file:
Dialog::Dialog(QWidget *parent)
{
createGUI();
reload();
}
Dialog::~Dialog(void) {};
void Dialog::reload(void)
{
restoreState();
}
void Dialog::createGUI(void)
{
QFile file(":/Resources/default.txt");
file.open(QIODevice::ReadOnly);
model = new TreeModel(file.readAll());
file.close();
view = new TreeView(this);
view->setModel(model);
QVBoxLayout *mainVLayout = new QVBoxLayout;
mainVLayout->addWidget(view);
setLayout(mainVLayout);
}
void Dialog::closeEvent(QCloseEvent *event_)
{
saveState();
}
void Dialog::saveState(void)
{
QStringList List;
// prepare list
// PS: getPersistentIndexList() function is a simple `return this->persistentIndexList()` from TreeModel model class
foreach (QModelIndex index, model->getPersistentIndexList())
{
if (view->isExpanded(index))
{
List << index.data(Qt::DisplayRole).toString();
}
}
// save list
QSettings settings("settings.ini", QSettings::IniFormat);
settings.beginGroup("MainWindow");
settings.setValue("ExpandedItems", QVariant::fromValue(List));
settings.endGroup();
}
void Dialog::restoreState(void)
{
QStringList List;
// get list
QSettings settings("settings.ini", QSettings::IniFormat);
settings.beginGroup("MainWindow");
List = settings.value("ExpandedItems").toStringList();
settings.endGroup();
foreach (QString item, List)
{
// search `item` text in model
QModelIndexList Items = model->match(model->index(0, 0), Qt::DisplayRole, QVariant::fromValue(item));
if (!Items.isEmpty())
{
// Information: with this code, expands ONLY first level in QTreeView
view->setExpanded(Items.first(), true);
}
}
}
Have a nice day!)
PS: this example based on C:\Qt\4.6.3\examples\itemviews\simpletreemodel code.
Thanks to Razi and mosg I was able to get this working. I made it restore the expanded state recursively so I thought I would share that part.
void applyExpandState_sub(QStringList& expandedItems,
QTreeView* treeView,
QAbstractItemModel* model,
QModelIndex startIndex)
{
foreach (QString item, expandedItems)
{
QModelIndexList matches = model->match( startIndex, Qt::UserRole, item );
foreach (QModelIndex index, matches)
{
treeView->setExpanded( index, true );
applyExpandState_sub(expandedItems,
treeView,
model,
model->index( 0, 0, index ) );
}
}
}
Then use like:
void myclass::applyExpandState()
{
m_treeView->setUpdatesEnabled(false);
applyExpandState_sub( m_expandedItems,
m_treeView,
m_model,
m_model->index( 0, 0, QModelIndex() ) );
m_treeView->setUpdatesEnabled(true);
}
I am using the Qt::UserRole here because multiple items in my model can have the same display name which would mess up the expand state restoration, so the UserRole provides a unique identifier for each item to avoid that problem.
These two function by using a loop should do that for you:
QModelIndexList QAbstractItemModel::persistentIndexList () const
bool isExpanded ( const QModelIndex & index ) const
Here is a general approach that should work with any QTreeView based widget, that uses some sort of ID system to identify elements (I am assuming the ID is an int, which is stored inside the Qt::UserRole):
void MyWidget::saveExpandedState()
{
for(int row = 0; row < tree_view_->model()->rowCount(); ++row)
saveExpandedOnLevel(tree_view_->model()->index(row,0));
}
void Widget::restoreExpandedState()
{
tree_view_->setUpdatesEnabled(false);
for(int row = 0; row < tree_view_->model()->rowCount(); ++row)
restoreExpandedOnLevel(tree_view_->model()->index(row,0));
tree_view_->setUpdatesEnabled(true);
}
void MyWidget::saveExpandedOnLevel(const QModelIndex& index)
{
if(tree_view_->isExpanded(index)) {
if(index.isValid())
expanded_ids_.insert(index.data(Qt::UserRole).toInt());
for(int row = 0; row < tree_view_->model()->rowCount(index); ++row)
saveExpandedOnLevel(index.child(row,0));
}
}
void MyWidget::restoreExpandedOnLevel(const QModelIndex& index)
{
if(expanded_ids_.contains(index.data(Qt::UserRole).toInt())) {
tree_view_->setExpanded(index, true);
for(int row = 0; row < tree_view_->model()->rowCount(index); ++row)
restoreExpandedOnLevel(index.child(row,0));
}
}
Instead of MyWidget::saveExpandedState() and MyWidget::saveExpandedState() one could also directly call MyWidget::saveExpandedOnLevel(tree_view_->rootIndex()) and MyWidget::restoreExpandedOnLevel(tree_view_->rootIndex()). I only used the above implementation because the for loop will be called anyway and MyWidget::saveExpandedState() and MyWidget::saveExpandedState() looked cleaner with my SIGNAL and SLOT design.
I have reworked iforce2d's solution into this:
void ApplyExpandState(QStringList & nodes,
QTreeView * view,
QAbstractItemModel * model,
const QModelIndex startIndex,
QString path)
{
path+=QString::number(startIndex.row()) + QString::number(startIndex.column());
for(int i(0); i < model->rowCount(startIndex); ++i)
{
QModelIndex nextIndex = model->index(i, 0, startIndex);
QString nextPath = path + QString::number(nextIndex.row()) + QString::number(nextIndex.column());
if(!nodes.contains(nextPath))
continue;
ApplyExpandState(nodes, view, model, model->index(i, 0, startIndex), path);
}
if(nodes.contains(path))
view->setExpanded( startIndex.sibling(startIndex.row(), 0), true );
}
void StoreExpandState(QStringList & nodes,
QTreeView * view,
QAbstractItemModel * model,
const QModelIndex startIndex,
QString path)
{
path+=QString::number(startIndex.row()) + QString::number(startIndex.column());
for(int i(0); i < model->rowCount(startIndex); ++i)
{
if(!view->isExpanded(model->index(i, 0, startIndex)))
continue;
StoreExpandState(nodes, view, model, model->index(i, 0, startIndex), path);
}
if(view->isExpanded(startIndex))
nodes << path;
}
This way there is no need to match data. Obviously - for this approach to work, tree needs to stay relatively unchanged. If you somehow change the order of tree items - it will expand wrong nodes.
Here is a version which doesn't rely on nodes having a unique Qt::UserRole or Qt::DisplayRole - it just serialises the entire QModelIndex
header:
#pragma once
#include <QTreeView>
class TreeView : public QTreeView
{
Q_OBJECT
public:
using QTreeView::QTreeView;
QStringList saveExpandedState(const QModelIndexList&) const;
void restoreExpandedState(const QStringList&);
};
source:
#include "tree_view.h"
#include <QAbstractItemModel>
namespace
{
std::string toString(const QModelIndex& index)
{
std::string parent = index.parent().isValid() ? toString(index.parent()) : "X";
char buf[512];
sprintf(buf, "%d:%d[%s]", index.row(), index.column(), parent.c_str());
return buf;
}
QModelIndex fromString(const std::string& string, QAbstractItemModel& model)
{
int row, column;
char parent_str[512];
sscanf(string.c_str(), "%d:%d[%s]", &row, &column, parent_str);
QModelIndex parent = *parent_str == 'X' ? QModelIndex() : fromString(parent_str, model);
return model.index(row, column, parent);
}
}
QStringList TreeView::saveExpandedState(const QModelIndexList& indices) const
{
QStringList list;
for (const QModelIndex& index : indices)
{
if (isExpanded(index))
{
list << QString::fromStdString(toString(index));
}
}
return list;
}
void TreeView::restoreExpandedState(const QStringList& list)
{
setUpdatesEnabled(false);
for (const QString& string : list)
{
QModelIndex index = fromString(string.toStdString(), *model());
setExpanded(index, true);
}
setUpdatesEnabled(true);
};
For a QFileSystemModel, you can't use persistentIndexList().
Here is my work around. It works pretty well, even if I do say so myself. I haven't tested to see what happens if you have a slow loading filesystem, or if you remove the file or path.
// scrolling code connection in constructor
model = new QFileSystemModel();
QObject::connect(ui->treeView, &QTreeView::expanded, [=](const QModelIndex &index)
{
ui->treeView->scrollTo(index, QAbstractItemView::PositionAtTop);//PositionAtCenter);
});
// save state, probably in your closeEvent()
QSettings s;
s.setValue("header_state",ui->treeView->header()->saveState());
s.setValue("header_geometry",ui->treeView->header()->saveGeometry());
if(ui->treeView->currentIndex().isValid())
{
QFileInfo info = model->fileInfo(ui->treeView->currentIndex());
QString filename = info.absoluteFilePath();
s.setValue("last_directory",filename);
}
// restore state, probably in your showEvent()
QSettings s;
ui->treeView->header()->restoreState(s.value("header_state").toByteArray());
ui->treeView->header()->restoreGeometry(s.value("header_geometry").toByteArray());
QTimer::singleShot(1000, [=]() {
QSettings s;
QString filename = s.value("last_directory").toString();
QModelIndex index = model->index(filename);
if(index.isValid())
{
ui->treeView->expand(index);
ui->treeView->setCurrentIndex(index);
ui->treeView->scrollTo(index, QAbstractItemView::PositionAtCenter);
qDebug() << "Expanded" << filename;
}
else
qDebug() << "Invalid index" << filename;
} );
Hope that helps someone.
My approach was to save the list of expanded items (as pointers) and when restoring, only set as expanded only the items in this list.
In order to use the code below, you may need to replace TreeItem * to a constant pointer to your object (that doesn't change after a refresh).
.h
protected slots:
void restoreTreeViewState();
void saveTreeViewState();
protected:
QList<TargetObject*> expandedTreeViewItems;
.cpp
connect(view->model(), SIGNAL(modelAboutToBeReset()), this, SLOT(saveTreeViewState()));
connect(view->model(), SIGNAL(modelReset()), this, SLOT(restoreTreeViewState()));
...
void iterateTreeView(const QModelIndex & index, const QAbstractItemModel * model,
const std::function<void(const QModelIndex&, int)> & fun,
int depth=0)
{
if (index.isValid())
fun(index, depth);
if (!model->hasChildren(index) || (index.flags() & Qt::ItemNeverHasChildren)) return;
auto rows = model->rowCount(index);
auto cols = model->columnCount(index);
for (int i = 0; i < rows; ++i)
for (int j = 0; j < cols; ++j)
iterateTreeView(model->index(i, j, index), model, fun, depth+1);
}
void MainWindow::saveTreeViewState()
{
expandedTreeViewItems.clear();
iterateTreeView(view->rootIndex(), view->model(), [&](const QModelIndex& index, int depth){
if (!view->isExpanded(index))
{
TreeItem *item = static_cast<TreeItem*>(index.internalPointer());
if(item && item->getTarget())
expandedTreeViewItems.append(item->getTarget());
}
});
}
void MainWindow::restoreTreeViewState()
{
iterateTreeView(view->rootIndex(), view->model(), [&](const QModelIndex& index, int depth){
TreeItem *item = static_cast<TreeItem*>(index.internalPointer());
if(item && item->getTarget())
view->setExpanded(index, expandedTreeViewItems.contains(item->getTarget()));
});
}
I think this implementation gives extra flexibility compared to some of the others here. At least, I could not make it work with my custom model.
If you want to keep new items expanded, change the code to save the collapsed items instead.