Is it possible to create a signal for when a QTreeWidgetItem checkbox is toggled?

Question

I've created a checkbox that's also a QTreeWidgetItem using the code below.

//Populate list
QTreeWidgetItem *program = createCheckedTreeItem(QString::fromStdString(itr->first), true);
treePrograms->addTopLevelItem(program);

---

QTreeWidgetItem* ConfigDialog::createCheckedTreeItem(QString name,bool checkBoxState)
{
  QTreeWidgetItem *item = new QTreeWidgetItem(QStringList(name));
  item->setFlags(item->flags()|Qt::ItemIsUserCheckable);
  if (checkBoxState)
  {
    item->setCheckState(0,Qt::Unchecked);
  }
  else
  {
    item->setCheckState(0,Qt::Checked);
  }
  return item;
}

I need a way of connecting a signal and slot for when the state of this checkbox is changed. The current way I've implemented this is below but unfortunately doesn't work. Can someone explain what I'm doing wrong and what I need to do in order to get it to connect?

connect(program, SIGNAL(toggled(bool)), this, SLOT(programChecked(bool)));

Answer 1

Your QTreeWidgetItem is directly linked to your model data, so you should connect to your QTreeWidget's model's QAbstractItemModel::dataChanged signal to be notified of the change.

Answer 2

You have to grab the signal itemChanged ( QTreeWidgetItem * item, int column ) coming from QTreeWidget.

Answer 3

Connect to the signal itemClicked(QTreeWidgetItem* item, int column) of the tree. When handling the signal, just verify item->checkState(column).

Answer 4

The best solution we found was to reimplement setData in an item subclass:

void MyItem::setData(int column, int role, const QVariant& value)
{
    const bool isCheckChange = column == 0
        && role == Qt::CheckStateRole
        && data(column, role).isValid() // Don't "change" during initialization
        && checkState(0) != value;
    QTreeWidgetItem::setData(column, role, value);
    if (isCheckChange) {
        MyTree *tree = static_cast<MyTree *>(treeWidget);
        emit tree->itemCheckStateChanged(this, checkState(0) == Qt::Checked);
    }
}

It would really be convenient to have this in Qt indeed, it makes me think about contributing a itemCheckStateChanged signal there directly :)

PS: setting Qt::ItemIsUserCheckable is unnecessary, this flag is on by default for all QTreeWidgetItems.