custom QAbstractTableModel class updating QTableView

[MichaH]

Hi all,

I already read a few threads on this forum dealing with similar issues but didn't provide "the" solution.

I built my own QAbstractTableModel class which fills a QTableView with data from a .csv file. The file is used for logging purposes and stores its (new) data every 10 minutes. The data is shown inside a QTableView but needs to be updated manually (button or closing and reopening the QDialog). What I want to achieve is that the view is automatically updated whenever new data is written to the .csv file.

The code snippets of my TableModel looks as follows:

int QCsvTableModel::rowCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    return csvMatrix.rowCount();
}
 
int QCsvTableModel::columnCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    return csvMatrix.columnCount();
}
 
QVariant QCsvTableModel::data(const QModelIndex &index, int role) const
{
    if (index.isValid())
        if (role == Qt::DisplayRole || role == Qt::EditRole)
            return csvMatrix.at(index.row(), index.column());
    return QVariant();
}
 
bool QCsvTableModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (index.isValid() && role == Qt::EditRole) {
        csvMatrix.setValue(index.row(), index.column(), value.toString());
 
        emit dataChanged(index,index);     // No difference if dataChanged is emitted or not
 
        return true;
    }
 
    return false;
}

int QCsvTableModel::rowCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    return csvMatrix.rowCount();
}

int QCsvTableModel::columnCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    return csvMatrix.columnCount();
}

QVariant QCsvTableModel::data(const QModelIndex &index, int role) const
{
    if (index.isValid())
        if (role == Qt::DisplayRole || role == Qt::EditRole)
            return csvMatrix.at(index.row(), index.column());
    return QVariant();
}

bool QCsvTableModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (index.isValid() && role == Qt::EditRole) {
        csvMatrix.setValue(index.row(), index.column(), value.toString());

        emit dataChanged(index,index);     // No difference if dataChanged is emitted or not

        return true;
    }

    return false;
}

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MainWindow source:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    QString fileName = ":/value.csv";
 
    if (!fileName.isEmpty()) {
        QCsvTableModel *model = new QCsvTableModel(this);
 
        QString extension = QFileInfo(QFile(fileName)).completeSuffix();
 
        if (extension.toLower() == "csv")     // known file extension
            model->loadFromFile(fileName);
 
        ui->tableView->setModel(model);
    } // if fileName ..
 
    connect(ui->tableView->model(), SIGNAL(dataChanged(const QModelIndex&, const QModelIndex&)), this, SLOT(onModelsDataChanged(const QModelIndex&, const QModelIndex&)));
    //connect(model, SIGNAL(dataChanged(const QModelIndex&, const QModelIndex&)), this, SLOT(onModelsDataChanged(const QModelIndex&, const QModelIndex&)));                         // Didn't work either ..
}
 
void MainWindow::onModelsDataChanged(const  QModelIndex  &topLeft,  const  QModelIndex  &bottomRight)
{
    Q_UNUSED(topLeft);
    Q_UNUSED(bottomRight);
 
    qDebug() << "The data has changed." << endl;
}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QString fileName = ":/value.csv";

    if (!fileName.isEmpty()) {
        QCsvTableModel *model = new QCsvTableModel(this);

        QString extension = QFileInfo(QFile(fileName)).completeSuffix();

        if (extension.toLower() == "csv")     // known file extension
            model->loadFromFile(fileName);

        ui->tableView->setModel(model);
    } // if fileName ..

    connect(ui->tableView->model(), SIGNAL(dataChanged(const QModelIndex&, const QModelIndex&)), this, SLOT(onModelsDataChanged(const QModelIndex&, const QModelIndex&)));
    //connect(model, SIGNAL(dataChanged(const QModelIndex&, const QModelIndex&)), this, SLOT(onModelsDataChanged(const QModelIndex&, const QModelIndex&)));                         // Didn't work either ..
}

void MainWindow::onModelsDataChanged(const  QModelIndex  &topLeft,  const  QModelIndex  &bottomRight)
{
    Q_UNUSED(topLeft);
    Q_UNUSED(bottomRight);

    qDebug() << "The data has changed." << endl;
}

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But the dataChanged() signal isn't fired at all and "The data has changed." never shows up.

What am I missing? Any help is appreciated!

Michael

[anda_skoa]

The code you posted does not contain any call to setData(), which is where you emit dataChanged().

Do you edit the table through the view?

Cheers,
_

[MichaH]

Hi anda_skoa,

thank you for replying!!
the model gets it's data from the loadFromFile() method which looks as follows:

bool QCsvTableModel::loadFromFile(const QString &fileName, const QChar &delim)
{
    beginResetModel();
 
    csvMatrix.clear();
    QChar delimiter;
    QFile file(fileName);
 
    if (delim == 0) {
        QString extension = QFileInfo(file).completeSuffix();
        if (extension.toLower() == "csv")
            delimiter = QChar(';');
    }
    else if (delim == QChar('"'))
            return false; //the ONLY invalid delimiter is double quote (")
    else
        delimiter = delim;
    if (!file.isOpen())
        if (!file.open(QFile::ReadOnly|QFile::Text))
            return false;
 
    QString temp;
    QChar lastCharacter;
    QTextStream in(&file);
    QList<QString> row;
 
    while (true) {
        QChar character;
        in >> character;
        if (in.atEnd()) {
            if (lastCharacter == delimiter) //cases where last character is equal to the delimiter
                temp = "";
            checkString(temp, row, csvMatrix, delimiter, QChar('\n'));
            break;
        } else if (character == delimiter || character == QChar('\n'))
            checkString(temp, row, csvMatrix, delimiter, character);
        else {
            temp.append(character);
            lastCharacter = character;
        }
    }
 
    file.close();
    in.flush();
    in.reset();
 
    return true;
 
    endResetModel();
}

bool QCsvTableModel::loadFromFile(const QString &fileName, const QChar &delim)
{
    beginResetModel();

    csvMatrix.clear();
    QChar delimiter;
    QFile file(fileName);

    if (delim == 0) {
        QString extension = QFileInfo(file).completeSuffix();
        if (extension.toLower() == "csv")
            delimiter = QChar(';');
    }
    else if (delim == QChar('"'))
            return false; //the ONLY invalid delimiter is double quote (")
    else
        delimiter = delim;
    if (!file.isOpen())
        if (!file.open(QFile::ReadOnly|QFile::Text))
            return false;

    QString temp;
    QChar lastCharacter;
    QTextStream in(&file);
    QList<QString> row;

    while (true) {
        QChar character;
        in >> character;
        if (in.atEnd()) {
            if (lastCharacter == delimiter) //cases where last character is equal to the delimiter
                temp = "";
            checkString(temp, row, csvMatrix, delimiter, QChar('\n'));
            break;
        } else if (character == delimiter || character == QChar('\n'))
            checkString(temp, row, csvMatrix, delimiter, character);
        else {
            temp.append(character);
            lastCharacter = character;
        }
    }

    file.close();
    in.flush();
    in.reset();

    return true;

    endResetModel();
}

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[anda_skoa]

That looks mostly good, but you need to do the endResetModel() before you return

Regarding your original question: since this method doesn't emit dataChanged() (doesn't need to since it resets the model), why would the slot connected to the signal be called?

Cheers,
_

[MichaH]

My bad! Did that already.

The code right now looks as follows:

bool QCsvTableModel::loadFromFile(const QString &fileName, const QChar &delim)
{
    QCsvTableModel::beginResetModel();
    csvMatrix.clear();
    QChar delimiter;
    QFile file(fileName);
 
    if (delim == 0) {
        QString extension = QFileInfo(file).completeSuffix();
        if (extension.toLower() == "csv")
            delimiter = QChar(';');
    }
    else if (delim == QChar('"'))
        return false; // The only invalid delimiter is double quote (")
    else
        delimiter = delim;
    if (!file.isOpen())
        if (!file.open(QFile::ReadOnly|QFile::Text))
            return false;
 
    QString temp;
    QChar lastCharacter;
    QTextStream in(&file);
    QList<QString> row;
 
    while (true) {
        QChar character;
        in >> character;
        if (in.atEnd()) {
            if (lastCharacter == delimiter) // Cases where last character is equal to the delimiter
                temp = "";
            checkString(temp, row, csvMatrix, delimiter, QChar('\n'));
            break;
        } else if (character == delimiter || character == QChar('\n'))
            checkString(temp, row, csvMatrix, delimiter, character);
        else {
            temp.append(character);
            lastCharacter = character;
        }
    }
 
    file.close();
    in.flush();
    in.reset();
 
    QCsvTableModel::endResetModel();
 
    return true;
}

bool QCsvTableModel::loadFromFile(const QString &fileName, const QChar &delim)
{
    QCsvTableModel::beginResetModel();
    csvMatrix.clear();
    QChar delimiter;
    QFile file(fileName);

    if (delim == 0) {
        QString extension = QFileInfo(file).completeSuffix();
        if (extension.toLower() == "csv")
            delimiter = QChar(';');
    }
    else if (delim == QChar('"'))
        return false; // The only invalid delimiter is double quote (")
    else
        delimiter = delim;
    if (!file.isOpen())
        if (!file.open(QFile::ReadOnly|QFile::Text))
            return false;

    QString temp;
    QChar lastCharacter;
    QTextStream in(&file);
    QList<QString> row;

    while (true) {
        QChar character;
        in >> character;
        if (in.atEnd()) {
            if (lastCharacter == delimiter) // Cases where last character is equal to the delimiter
                temp = "";
            checkString(temp, row, csvMatrix, delimiter, QChar('\n'));
            break;
        } else if (character == delimiter || character == QChar('\n'))
            checkString(temp, row, csvMatrix, delimiter, character);
        else {
            temp.append(character);
            lastCharacter = character;
        }
    }

    file.close();
    in.flush();
    in.reset();

    QCsvTableModel::endResetModel();

    return true;
}

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I just need to update the data structure with replacing the csvMatrix variable since it gets all the model data. But apparently I'm completely lost on that one right now........

[anda_skoa]

I am not sure I understand the current state correctly.

Still something you need help with?

Cheers,
_

[MichaH]

Well yes. The auto-update still doesn't work since I'm not able to figure out what else I'm missing..

[anda_skoa]

But the initial loading works?

Are you calling the same load method for updating or do you use something else?

Cheers,
_

[MichaH]

The data shows up in my QTableView correctly but still when the data of the csv file changes (doesn't matter if that happens outside of the qt app or with a button which adds new data) it doesn't update/refresh itself. It only refreshes if the app is restarted or if the QDialog is closed and reopened.

[anda_skoa]

How do you handle these two cases?

Do you watch the file for changes and then call the load method?

What do you do in the slot connected to the button? Also reload the file?

Cheers,
_

[MichaH]

When opening the dialog I've connected the dataChanged() signal to a slot which shows a debug message in the console. the connect() call returns true in debug.

{
...
connect(model, SIGNAL(dataChanged(const QModelIndex&, const QModelIndex&)), this, SLOT(onModelsDataChanged(const QModelIndex&, const QModelIndex&)));
...
}
 
void Dialog::onModelsDataChanged(const  QModelIndex  &topLeft,  const  QModelIndex  &bottomRight)
{
    Q_UNUSED(topLeft);
    Q_UNUSED(bottomRight);
 
    qDebug() << "YES" << endl;
 
//    model->loadFromFile(fileName);   // fileName = path/to/value.csv
//    ui->tableView->setModel(model);
}

{
...
connect(model, SIGNAL(dataChanged(const QModelIndex&, const QModelIndex&)), this, SLOT(onModelsDataChanged(const QModelIndex&, const QModelIndex&)));
...
}

void Dialog::onModelsDataChanged(const  QModelIndex  &topLeft,  const  QModelIndex  &bottomRight)
{
    Q_UNUSED(topLeft);
    Q_UNUSED(bottomRight);

    qDebug() << "YES" << endl;

//    model->loadFromFile(fileName);   // fileName = path/to/value.csv
//    ui->tableView->setModel(model);
}

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The commented lines (reloading the model) didn't make any difference.

The button just increments a number when it's clicked and writes it to the file:

void Dialog::onButtonPush()
{
    QFile log(":/value.csv");
 
    QTextStream stream(&log);
    x++;
 
    if (log.open(QFile::WriteOnly | QFile::Truncate)) {
        stream << "Clicked button number;" << x << endl;
        ui->pushButton->setText(QString::number(x));
    }
 
    log.flush();
    log.close();
}

void Dialog::onButtonPush()
{
    QFile log(":/value.csv");

    QTextStream stream(&log);
    x++;

    if (log.open(QFile::WriteOnly | QFile::Truncate)) {
        stream << "Clicked button number;" << x << endl;
        ui->pushButton->setText(QString::number(x));
    }

    log.flush();
    log.close();
}

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Button and tableview are on the same dialog window and the tableview is supposed to be updated as soon as the data changes - e.g. every time the button is clicked. The updating doesn't work though. :/