Question

could someone please tell me, why this code for the freaking hell, doesn’t display data in a view?

#include <QApplication>
#include <QtGui>

class File_Model : public QAbstractItemModel
{
private:
    QStringList data_;
public:

    File_Model()
    {}
    QVariant data(const QModelIndex &index, int role) const
    {


        return data_.at(index.row());
    }

    bool setData(const QModelIndex &index, const QVariant &value, int role = Qt::DisplayRole)
    {
        switch(role)
        {
        case Qt::DisplayRole:
        data_ =  value.toStringList();
        emit dataChanged(index,index);
        return true;
        }
        return false;
    }

    virtual QModelIndex index(int row, int column, const QModelIndex&) const
    {
        return createIndex(row,column);
    }
    virtual QModelIndex parent(const QModelIndex&) const
    {
        return QModelIndex();
    }
    virtual int rowCount(const QModelIndex&) const
    {
        return data_.size();
    }
    virtual int columnCount(const QModelIndex&) const
    {
        return 1;
    }
};


int main(int argc,char** argv)
{
    QApplication app(argc,argv);
    QDir dir(QDesktopServices::storageLocation(QDesktopServices::HomeLocation));
    File_Model* model = new File_Model;//(dir.entryList());
   bool t =  model->setData(QModelIndex(),dir.entryList());
    QListView* view = new QListView;
    view->setModel(model);

    view->show();

    return app.exec();
}

Answer 1

The problem is on your data function. You should check the role before displaying something:

QVariant data(const QModelIndex &index, int role) const
{
    if (role == Qt::DisplayRole)
        return QVariant(data_.at(index.row()));

    return QVariant();
}

Also note that you don’t have to use the setData in your case. setData is udes for editing models, not initializing them with some values.

To enable editing in your model, you must also implement setData(),
and reimplement flags() to ensure that ItemIsEditable is returned.

Instead you could add a public function in your model and call it instead:

void setEntries(QStringList entries)
{
    beginInsertRows(createIndex(0,0), 0, entries.count());
    data_ =  entries;
    endInsertRows();
}