QListView, headerdata and data never called

Athius

Hi everyone,

I just want to create a model that contains two custom datas (two QString) and display it in a QListView.
I have some issue: nothing is shown when I insert a new row and a new data inside it.

I join you my model. m_items is a QList of ImageSegmentationItem (a class with two QString).

When I debug my code, I never go inside the headerData method neither data method.
I don't understand what I did wrong.

Thank you

ImageSegmentationModel::ImageSegmentationModel(QObject *parent)
	: QAbstractListModel(parent)
{
}

QVariant ImageSegmentationModel::headerData(int section, Qt::Orientation orientation, int role) const
{
	if (orientation == Qt::Horizontal && role == Qt::DisplayRole)
	{
		if (section == 0)
		{
			return tr("Image Path");
		}
		else if (section == 1)
		{
			return tr("Segmentation Path");
		}
	}
	return QVariant();
}

int ImageSegmentationModel::rowCount(const QModelIndex &parent) const
{
	return m_items.size();
}

int ImageSegmentationModel::columnCount(const QModelIndex &parent) const
{
	return 2;
}

QVariant ImageSegmentationModel::data(const QModelIndex &index, int role) const
{
	if (!index.isValid())
		return QVariant();

	if (role == Qt::DisplayRole)
	{
		if (index.column() == 0)
		{
			return m_items.at(index.row()).imagePath();
		}
		else if (index.column() == 1)
		{
			return m_items.at(index.row()).segmentationPath();
		}
	}

	return QVariant();
}

bool ImageSegmentationModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
	bool res = false;
	if (index.isValid() && role == Qt::EditRole)
	{
		if (m_items.size() > index.row())
		{
			if (value.canConvert<QString>())
			{
				QString valStr = value.toString();
				if (index.column() == 0)
				{
					m_items[index.row()].setImagePath(valStr);
					res = true;
				}
				else if (index.column() == 1)
				{
					m_items[index.row()].setSegmentationPath(valStr);
					res = true;
				}
			}
			if (res)
			{
				emit dataChanged(index, index);
			}
		}
	}
	return res;
}

Edit: I remove the test on the parent in the rowCount method and now, the line are show but only the first column (still without the header)

Christian Ehrlicher

@Athius said in QListView, headerdata and data never called:

but only the first column

https://doc.qt.io/qt-5/qabstractlistmodel.html#details :
"The QAbstractListModel class provides an abstract model that can be subclassed to create one-dimensional list models."

So why should it be called for the second column? Looks like you want QAbstractTableModel instead.

Athius

@Christian-Ehrlicher said in QListView, headerdata and data never called:

So why should it be called for the second column? Looks like you want QAbstractTableModel instead.

Thank you.

Because I thought that by overloading the columnCount method and always returning 2, the problem will fix but no.
I change by a QAbstractTableModel and also by QAbstractItemModel before I understand that the problem was coming from the view: I change the QListView by a QTableView and it's all working now (I keep the model as described before).

Christian Ehrlicher

@Athius said in QListView, headerdata and data never called:

Because I thought that by overloading the columnCount method and always returning 2

A QAbstractListModel is made for 1 column, you misuse the desired usecase. This can lead to unexpected things. If you want a table, use a table and not a chair.