Select specific item in QListView

[Cerberus]

I have a QListView which contents I said with a Model. When resetting the model I need to reselect the previous item but I'm not sure how to search for it and than select it.
This is how I set the model:

void IMClientGui::setActiveUsers(QSqlQueryModel *sqm) {
    QString currentUser = this->getSelectedHost();
    ui->clientsOnline->setModel(sqm);
    //here the old selection should be reset if this entry is still in the list
}
 
QString IMClientGui::getSelectedHost() {
    auto itemselectmodel = ui->clientsOnline->selectionModel();
 
    if (itemselectmodel->selectedIndexes().size() > 0) {
        QModelIndex index = itemselectmodel->selectedIndexes().at(0);
        return index.data().toString();
    } else
        return "";
}

void IMClientGui::setActiveUsers(QSqlQueryModel *sqm) {
    QString currentUser = this->getSelectedHost();
    ui->clientsOnline->setModel(sqm);
    //here the old selection should be reset if this entry is still in the list
}

QString IMClientGui::getSelectedHost() {
    auto itemselectmodel = ui->clientsOnline->selectionModel();

    if (itemselectmodel->selectedIndexes().size() > 0) {
        QModelIndex index = itemselectmodel->selectedIndexes().at(0);
        return index.data().toString();
    } else
        return "";
}

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I cannot work with the indexes here (e.g. if item with index 3 was selected reset to index 3) since a previous item might have been removed and therefore the index could be less or more if an item was added

[anda_skoa]

See QAbstractItemModel::match() for finding a model index with certain data.

Cheers,
_

[Cerberus]

I'm not sure how to use this method, what exactly am i supposed to put as QModelIndex and role? And how do I define the QVariant, in my case the displayed values are all QStrings?

[ChrisW67]

QModelIndexList indexes = model->match(
  model->index(0,0),  // first row, first column
  Qt::DisplayRole,  // search the text as displayed
  stringValue,  // there is a QVariant(QString) conversion constructor
  1, // first hit only
  Qt::MatchExactly // or Qt::MatchFixedString
);

QModelIndexList indexes = model->match(
  model->index(0,0),  // first row, first column
  Qt::DisplayRole,  // search the text as displayed
  stringValue,  // there is a QVariant(QString) conversion constructor
  1, // first hit only
  Qt::MatchExactly // or Qt::MatchFixedString
);

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[Cerberus]

When executing this

auto model = ui->clientsOnline->selectionModel()->model();
 
    QModelIndexList indexes = model->match(
      model->index(0,0),  // first row, first column
      Qt::DisplayRole,  // search the text as displayed
      currentUser,  // there is a QVariant(QString) conversion constructor
      1, // first hit only
      Qt::MatchExactly // or Qt::MatchFixedString
    );

auto model = ui->clientsOnline->selectionModel()->model();

    QModelIndexList indexes = model->match(
      model->index(0,0),  // first row, first column
      Qt::DisplayRole,  // search the text as displayed
      currentUser,  // there is a QVariant(QString) conversion constructor
      1, // first hit only
      Qt::MatchExactly // or Qt::MatchFixedString
    );

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I get a Segmentation fault!?

[ChrisW67]

So model is 0 or invalid. Why are you going via the selection model anyway?

Something like this:
When the data model emits modelAboutToBeReset() you want to store the current value selected in the list view.

const QModelIndex currentIndex = ui->clientsOnline->currentIndex();  // may be an invalid index
m_previouslySelected = (currentIndex.isValid())? currentIndex->data(Qt::DisplayRole): QVariant();

const QModelIndex currentIndex = ui->clientsOnline->currentIndex();  // may be an invalid index
m_previouslySelected = (currentIndex.isValid())? currentIndex->data(Qt::DisplayRole): QVariant();

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When the data model later emits modelReset() find and restore the list view's current item if possible:

if (!m_previouslySelected.isNull()) {
  const QAbstractItemModel *model = ui->clientsOnline->model();
  const QModelIndexList indexes = model->match(
      model->index(0,0),
      Qt::DisplayRole,
      m_previouslySelected, 
      1, // first hit only
      Qt::MatchExactly
    );
  if (index.size() > 0) {  // found a match
    ui->clientsOnline->setCurrentIndex(indexes.at(0));
  }
}

if (!m_previouslySelected.isNull()) {
  const QAbstractItemModel *model = ui->clientsOnline->model();
  const QModelIndexList indexes = model->match(
      model->index(0,0),
      Qt::DisplayRole,
      m_previouslySelected, 
      1, // first hit only
      Qt::MatchExactly
    );
  if (index.size() > 0) {  // found a match
    ui->clientsOnline->setCurrentIndex(indexes.at(0));
  }
}

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[Cerberus]

Worked thanks