Show other data in QTableView with QItemDelegate

Question

I have a QTableView connected with an QSqlTableModel.
In the first column, there are only dates at this format: 2010-01-02
I want this column to show the date at this format (but without changing the real data): 02.01.2010
I know that I have to create an QItemDelegate for this column, but I don't know how I can read the existing data and overwrite it with something different. You have any idea how to manage that?

Vasya

Answer 1

An item delegate doesn't necessarily change the data, it just renders the data. Also, if you're using Qt 4.4 or newer, look at QStyledItemDelegate instead--it's theme-aware and will look nicer.

There's an example of item delegates in this article (which seems to be a mirror of official documentation that is now down or gone).

Since all you really want to do is customize the text, have you considered using a proxy model instead and just returning your custom QString for the date column's DisplayRole?

Obey

Either the delegate or the proxy model would work pretty well in this situation. The delegate is probably closer to what what intended, however. – Pulverable

my problem is, that i don't get how to make it with an QItemDelegate. the paint()-method will not work for me – Vasya

What, specifically, is the problem with paint()? – Obey

i know how to get the data ( qVariantValue<QString>(index.data()) ), but i don't know how to overwrite it with "foo" for example – Vasya

This is where using a proxy model will come in handy, as it's easier to support row/column/type-specific hacks there, but since you apparently really want a delegate... Create a QStyledItemDelegate subclass which reimplements paint() and sizeHint(). These implementations should actually check whether index.data() returns a QDate in the variant; if not, they should just call the base class's implementation. If so, do your own string conversion and either measure it (for sizeHint()) or draw it (for paint()). – Obey

Answer 2

The simplest solution is to create a QStyledItemDelegate subclass and reimplement displayText(...) ie

class DateFormatDelegate : public QStyledItemDelegate
{
public:
 DateFormatDelegate (QString dateFormat, QObject *parent = 0) : 
  QStyledItemDelegate(parent),
  m_dateFormat(dateFormat)
 {
 }

 virtual QString displayText(const QVariant & value, const QLocale & locale ) const
 {
  Q_UNUSED(locale);
  return value.toDate().toString(m_dateFormat);
 }

private:
 QString m_dateFormat;
};

Then in your view -

setItemDelegateForColumn(/*date column*/, new DateFormatDelegate("MM.dd.yyyy", this));

Biolysis