QTableWidget signal when item dropped

[Jeffb]

Hi Guys

Before I go and subclass QTableWidget, does anyone know of a signal or some other way I can be alerted when an item is dropped in a QTableWidget?
Or do I have to subclass it and reimplement QDropEvent?

Thanks
Jeff

[Spitfire]

As far as I know there's no such signal but you could install an event filter on the table widget and handle the drop there instead of using a signal.

[AlexSudnik]

Just reimplement QWidget::dragEnterEvent( QDragEnterEvent * event ) function.

[Jeffb]

Couldn't get the event filter working - I'm assuming it has something to do with QTableWidget having its own implementation of QEvent and QDropEvent.
Reimplementing dragEnterEvent was no good to me as I need to know when an item had actually been dropped - a dragEnterEvent fires regardless of whether the item is dropped or not.
As it is I just subclassed QTableWidget and reImplemented QDropEvent with the following code:

void JB_QTableWidget::dropEvent(QDropEvent * event)
{
    QTableWidget::dropEvent(event);
    emit itemDropped();
    event->accept();
}

void JB_QTableWidget::dropEvent(QDropEvent * event)
{
    QTableWidget::dropEvent(event);
    emit itemDropped();
    event->accept();
}

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[AlexSudnik]

Hm , what about to emit signal before event is handled by QTableWidget::dropEvent , also don't see a point in "event->accept()". I mean , i think event will be already handled at this point.
Anyway , i've used to to use QWidget for drag/drop implementation...and any signals' emission seem to work just fine.Here is code snippet :

void MyWidget::dragEnterEvent( QDragEnterEvent * event )
{
	if( event->provides( ApplicationConstants::supportedMIMEdata) ) event->acceptProposedAction(); // make sure that data being droped can be handled.
}
 
void MyWidget::dropEvent( QDropEvent * event  )
{
 
		const QMimeData* data = event->mimeData();
 
                // ...
 
		emit dataIsDroped(); 
 
}

void MyWidget::dragEnterEvent( QDragEnterEvent * event )
{
	if( event->provides( ApplicationConstants::supportedMIMEdata) ) event->acceptProposedAction(); // make sure that data being droped can be handled.
}

void MyWidget::dropEvent( QDropEvent * event  )
{
				
		const QMimeData* data = event->mimeData();

                // ...
		
		emit dataIsDroped(); 
		
}

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[Spitfire]

If the drop signal is the only thing you want and will be used in a signgle place then subclassing is an overkill.

Just use event filter like I've mentioned earlier:

bool    MainWindow::eventFilter( QObject* o, QEvent* e )
{
    if( o == this->table->viewport() && e->type() == QEvent::Drop )
    {
        // do what you would do in the slot
        qDebug() << "drop!";
    }
 
    return false;
}

bool    MainWindow::eventFilter( QObject* o, QEvent* e )
{
    if( o == this->table->viewport() && e->type() == QEvent::Drop )
    {
        // do what you would do in the slot
        qDebug() << "drop!";
    }

    return false;
}

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10 lines of code is all you need.

In case you don't know how to install even filter here's how:

MainWindow::MainWindow( QWidget* p )
    :
    QMainWindow( p ),
    table( new QTableWidget() )
{
    this->table->setColumnCount( 10 );
    this->table->setRowCount( 10 );
    this->table->setDragEnabled( true );
    this->table->setDragDropMode( QAbstractItemView::DragDrop );
    this->table->viewport()->installEventFilter( this ); // that's what you need
 
    this->setCentralWidget( this->table );
}

MainWindow::MainWindow( QWidget* p )
    :
    QMainWindow( p ),
    table( new QTableWidget() )
{
    this->table->setColumnCount( 10 );
    this->table->setRowCount( 10 );
    this->table->setDragEnabled( true );
    this->table->setDragDropMode( QAbstractItemView::DragDrop );
    this->table->viewport()->installEventFilter( this ); // that's what you need

    this->setCentralWidget( this->table );
}

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