QtableView, need to clear selection index after removing a row

[lansing]

I have a tableview with data and a remove button. When I selected a row and clicked on the button, the row was removed with no selection in the view. But when I clicked the button again, another row was removed without me selecting anything.

This is the remove slot function in my main dialog.

void MyDialog::slotRemoveData()
{
    QModelIndex index = ui->myTableView->currentIndex();
    m_myModel->removeData(index);
}

myModel.cpp

void MyModel::removeData(const QModelIndex &parent)
{
    if (!parent.isValid())
        return;

    int row = parent.row();

    beginRemoveRows(QModelIndex(), row, row);
    m_myData.remove(row);
    endRemoveRows();
}

I think what happen was that the currentIndex was not cleared after the first remove call, so when I called remove again, it removed the new row that took place of the index.

There's a clearSelection() in the document but it stated that the current index will not be changed. What is the correct way to deselect it after the first remove?

[gde23]

you can make the current index invalid after removing the row:

void MyDialog::slotRemoveData()
{
    QModelIndex index = ui->myTableView->currentIndex();
    m_myModel->removeData(index);
    setCurrentIndex(QModelIndex()); 
}

[JonB]

@lansing
Purely a guess: would ui->myTableView->setCurrentIndex(QIndex()) work for you?

[lansing]

@gde23 @JonB

Thanks guy this works. I also want to know why it works. What does QModelIndex means when passed into setCurrentIndex()?

[VRonin]

Don't use currentIndex(). That one record the last item that was "activated", it does not record selected indexes. You should use ui->myTableView->selectionModel()->selectedIndexes() instead

[lansing]

@VRonin

Hi I just tested it, this still requires to set tableView's current index after remove.

[JonB]

@VRonin said in QtableView, need to clear selection index after removing a row:

That one record the last item that was "activated"

Thanks! I had never understood that was the definition, I don't think the docs tell you that (that I came across?), they just seem to tell you it's the "current" one!

[JoeCFD]

This post is deleted!

[JonB]

@lansing said in QtableView, need to clear selection index after removing a row:

What does QModelIndex means when passed into setCurrentIndex()?

QModelIndex() is the default-constructed one, https://doc.qt.io/qt-5/qmodelindex.html#QModelIndex

Creates a new empty model index. This type of model index is used to indicate that the position in the model is invalid.

In your MyModel::removeData() code it would hit your if (!parent.isValid()) return;.

[BTW: Since you have a QTableView, not a QTreeView, I don't think you're doing yourself/myself any clarity favours by naming your parameter parent here? There is no parentage, plain const QModelIndex &index would not be misleading.]

[lansing]

@VRonin This is the code I tested

QModelIndexList indexList= ui->myTableView->selectionModel()->selectedIndexes();

if (!indexList.isEmpty()){
    m_myModel->removeData(indexList.first());
}

This still doesn't deselect the index after remove.

[lansing]

@JonB

Those templates were created by Qt Creator, I was just going with them without knowing much.

[VRonin]

@lansing

const QModelIndexList indexList= ui->myTableView->selectionModel()->selectedIndexes();
for(auto& i : indexList)
    m_myModel->removeData(i);
ui->myTableView->selectionModel()->select(ui->myTableView->selectionModel()->selection(),QItemSelectionModel::Deselect);

[lansing]

@VRonin

I use a vector in my model to hold the data, and for some reason this code is removing 3 rows at a time.

[lansing]

I solved my last problem with a check on empty indexList and removing only indexList.first().

    const QModelIndexList indexList= ui->myTableView->selectionModel()->selectedIndexes();

    if (indexList.isEmpty()){
           return;
        }

    m_myModel->removeData(indexList.first());

    ui->myTableView->selectionModel()->select(
                ui->myTableView->selectionModel()->selection(),
                QItemSelectionModel::Deselect);

Now I come into another problem trying to remove all. In my model I just called vector::clear() to clear my vector whose holding the data.

void MyModel::clearAll()
{
    if (!m_myData.isEmpty()) {
        m_myData.clear();
    }
}

There are two problems, I don't know what signal I should be emitting. And my view doesn't update with the model.

myDialog.cpp

void MyDialog::slotRemoveAll()
{
    m_myModel->clearAll();
}

After calling this slot, all my data in the model were cleared, but the table grids still remained.

[JonB]

@lansing said in QtableView, need to clear selection index after removing a row:

There are two problems, I don't know what signal I should be emitting. And my view doesn't update with the model.

I think these are one problem :) When the model signal is right, the view should update. You have deleted all rows, so you need to emit QAbstractItemModel::rowsRemoved(const QModelIndex &parent, int first, int last), or do begin/endRemoveRows(), with the original number of rows. Or, I think you can do QAbstractItemModel::begin/endResetModel().

[lansing]

@JonB

Thank you begin/endResetModel() solved it.