TreeView getting all children in a TreeItemModel is empty

DJViking

I am new to Qt. Trying to learn. I am using Qt 5, since it comes with my Linux distribution KDE, I wanted to use that version instead of Qt 6.

I am having some trouble with TreeView and TreeItemModel.

I am using the QStandardItemModel and QStandardItem classes.
Though I have made my own subclasses of them.

class SubsystemItemModel : public QStandardItemModel
class SubsystemItem : public QStandardItem

I did try to follow the Simple Tree Model Example, but found it a bit complex. I found using QAbstractItemModel was a bit to complex for my level of Qt understanding. To much I had to implement on my own, and I did not need multiple columns in my TreeView data.
https://doc.qt.io/qt-5/qtwidgets-itemviews-simpletreemodel-example.html

I am trying to get all the children in the model, all the items.
I have tried getting them by calling both of these two methods on the QStandardItemModel
https://doc.qt.io/qt-5/qobject.html#children
https://doc.qt.io/qt-5/qobject.html#findChildren

However both lists are empty.

    SubsystemItemModel subsystem_model = new SubsystemItemModel(mw, this);
    subsystem_model->setHorizontalHeaderLabels(QStringList() << "Subsystems");

    QTreeView *treeView = ui->subsystemTreeView;
    treeView->setModel(subsystem_model);

    SubsystemItem *item0 = new SubsystemItem("TEST");
    subsystem_model->appendRow(item0);

    SubsystemItem *item01 = new SubsystemItem("TEST.SUBTEST_1");
    item0->appendRow(item01);
    SubsystemItem *item02 = new SubsystemItem("TEST.SUBTEST_2");
    item0->appendRow(item02);
    SubsystemItem *item03 = new SubsystemItem("TEST.SUBTEST_3");
    item0->appendRow(item03);
    SubsystemItem *item04 = new SubsystemItem("TEST.SUBTEST_4");
    item0->appendRow(item04);
    SubsystemItem *item05 = new SubsystemItem("TEST.SUBTEST_5");
    item0->appendRow(item05);

    std::cout << "children" << std::endl;
    QObjectList children = subsystem_model->children();
    foreach (auto obj, children) {
      std::cout << "child " << obj->objectName().toStdString() << std::endl;
    }

    std::cout << "findChildren" << std::endl;
    QList<QObject*> list = subsystem_model->findChildren<QObject*>();
    foreach (auto obj, children) {
      std::cout << "child " << obj->objectName().toStdString() << std::endl;
    }

The items are shown in the TreeView when I run my application, but both these lists are empty.

JonB

This post is deleted!

Christian Ehrlicher

Since QStandardItem is not derived from QObject neither children() nor qFindChild() can return them.
You're looking for invisibleRootItem() where you then can traverse through all the child items.

DJViking

@Christian-Ehrlicher
I thought so too. I was checking into using the invisibleRootItem(), but cannot find which method to call upon.
https://doc.qt.io/qt-5/qstandarditem.html

I tried this, but I am not getting all the children.

    QStandardItem *rootItem = subsystem_model->invisibleRootItem();
    auto rowCount = rootItem->rowCount();
    std::cout << "Rows " << std::to_string(rowCount) << std::endl;
    for (int row = 0; row < rowCount; ++row)
    {
        QStandardItem *item = rootItem->child(row);
        std::cout << item->text().toStdString() << std::endl;
    }

The rowCount=1. I guess that is right, considering I only have one row added on the model. Then the first row has 5 items.
Do I need to recursive traverse my self to get all items?

Christian Ehrlicher

@DJViking said in TreeView getting all children in a TreeItemModel is empty:

Do I need to recursive traverse my self to get all items?

Yes, it's a tree.