How to catch "change selected row" signal in a QTableView?

jdent

In QTableWidget one can connect

 &QTableWidget::cellChanged

to a slot you provide
How is this done for QTableView?

Pl45m4

@jdent said in How to catch "change selected row" signal in a QTableView?:

How is this done for QTableView?

There is no such function, but you can implement a signal like this on your own.

Looking at the QTableWidget source where cellChanged is emitted:

void QTableWidgetPrivate::_q_emitItemChanged(const QModelIndex &index)
{
    Q_Q(QTableWidget);
    if (QTableWidgetItem *item = tableModel()->item(index))
        emit q->itemChanged(item);
    emit q->cellChanged(index.row(), index.column());
}

https://codebrowser.dev/qt6/qtbase/src/widgets/itemviews/qtablewidget.cpp.html#_ZN19QTableWidgetPrivate18_q_emitItemChangedERK11QModelIndex

void QTableWidgetPrivate::_q_emitItemChanged emits cellChanged and is a private (hidden) function used in QTableWidget to make it work as we all know. But you can add this behaviour to your own QTableView subclass.

void QTableWidgetPrivate::setup()
{
    Q_Q(QTableWidget);
    // model signals
    QObject::connect(model, SIGNAL(dataChanged(QModelIndex,QModelIndex)),
                         q, SLOT(_q_emitItemChanged(QModelIndex)));
}

You see here, that this function from above is connected to the dataChanged(index, index) signal of the model during the initialization of the QTableWidget and its private logic.

model is a QAbstractItemModel* internally.
You can use your model, of course.

SGaist

@jdent hi,

Something is not clear between your title and post content. The title mentions selection but the post is about cellChanged which are about two different things.

If you are thinking about selection, then take a look at QItemSelectionModel.

jdent

to be clear I am going to copy my code:

VectorModel* model = new VectorModel{};
QSortFilterProxyModel* proxy = new QSortFilterProxyModel{ this };
proxy->setSourceModel(model);
ui.tableView->setModel(proxy);
ui.tableView->setSortingEnabled(true);


QDataWidgetMapper* mapper = new QDataWidgetMapper{};
mapper->setModel(proxy);
mapper->addMapping(ui.lineEdit, 0);
mapper->addMapping(ui.lineEdit_2, 1);
mapper->toFirst();

QItemSelectionModel* selection_model = new QItemSelectionModel{ proxy };


connect(selection_model, &QItemSelectionModel::currentRowChanged , this, &QtWidgetsApplication1::currentRowChanged);

But changing the selection in the QTableView does not trigger the currentRowChanged signal!!

SGaist

What about using the selection model from the table view directly ?

jdent

How can I use the selectionModel of my VectorModel? My model inherits from QAbstractTableModel but I don't see any selectionModel in QAbstractTableModel functions/properties...

SGaist

Sorry, I miswrote my answer (fixed it by the way). The selection model is returned by the view you are using. See selectionModel.

I meant to say, use that one directly.

JonB

@jdent
Your question and @SGaist's answer happen to relate to the reply I have just posted at https://forum.qt.io/topic/157167/what-should-i-do-to-use-treeview-childs-to-select-a-subset-of-data-to-show-in-a-tableview/2. As I wrote there, see e.g. See e.g. https://stackoverflow.com/questions/2062889/qtableview-what-signal-is-sent-when-user-selects-a-row-by-clicking-to-it for use of selectionModel(). Selection is handled by the view.

jdent

I have access to selection Model as @SGaist recommended and I wrote:

    QItemSelectionModel* selection_model = ui.tableView->selectionModel();
    connect(selection_model, &QItemSelectionModel::currentRowChanged , this, &QtWidgetsApplication1::currentRowChanged);

But I have a mapper like this:

    mapper = new QDataWidgetMapper{};
    mapper->setModel(proxy);
    mapper->addMapping(ui.lineEdit, 0);
    mapper->addMapping(ui.lineEdit_2, 1);
    mapper->toFirst();

and I need the mapper to "move to the new selected row", something like mapper->to(n) where n is the new current selection
so that the form widgets (e.g. ui.lineEdit) are kept in sync with the table view selection but how?

JonB

@jdent
Are you asking about void QDataWidgetMapper::setCurrentModelIndex(const QModelIndex &index)

Sets the current index to the row of the index if the orientation is horizontal (the default), otherwise to the column of the index.
This convenience slot can be connected to the signal currentRowChanged()

connect(myTableView->selectionModel(), &QItemSelectionModel::currentRowChanged,
        mapper, &QDataWidgetMapper::setCurrentModelIndex);