drag and drop with item views

[wysota]

Models? Or views? QTreeView and QListView are views not models... And are you sure you need to subclass them? It is rarely needed...

[castorvert]

I meant I had 2 models associated with my 2 views. I'll try not to subclass my views but to use the original ones. In fact, I thought I had to define custom functions for drag and drop in my views, that's why I subclassed the Qt views.

[castorvert]

Well, I thought about it, and in my opinion, even if I don't define custom functions, it's better to subclass the view because when I create my object, I can define the delegate, the colour, the setDropEnabled ...

[castorvert]

I found sth strange : when I subclass QAbstractListModel, I have to subclass flags() to have Drag and drop enabled. In QAbstractItemModel, there is only :

Qt::ItemFlags QAbstractItemModel::flags(const QModelIndex &index) const
{
    if (!index.isValid())
        return 0;
 
    return Qt::ItemIsSelectable|Qt::ItemIsEnabled;
}

Qt::ItemFlags QAbstractItemModel::flags(const QModelIndex &index) const
{
    if (!index.isValid())
        return 0;

    return Qt::ItemIsSelectable|Qt::ItemIsEnabled;
}

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[wysota]

Well, I thought about it, and in my opinion, even if I don't define custom functions, it's better to subclass the view because when I create my object, I can define the delegate, the colour, the setDropEnabled ...

You don't have to subclass to do that. You use that view only once, so there is no point is subclassing.

I found sth strange : when I subclass QAbstractListModel, I have to subclass flags() to have Drag and drop enabled.

There is nothing strange in it. flags() from abstract item model just implements the most common behaviour. If you want to have a more complicated model, you have to reimplement flags() along with other modelling methods.

[castorvert]

Thank you, i've finally understood what mimeTypes() is.
I have another question, if you please.

Let's take an example :

-I defined supportedDropActions() in a model as following :

Qt::DropActions ModeleDispos::supportedDropActions() const{
		return Qt::MoveAction;
	}

Qt::DropActions ModeleDispos::supportedDropActions() const{
		return Qt::MoveAction;
	}

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-I defined removeRows too.
-In "QAbstractItemView", it seems that "startDrag" and "dropEvent" use "supportedDropActions" so I think it's possible to move an item into the same view.
-the mimeTypes and mimeData are of the same Type.
but I couldn't move an item into the model.

It worked when I did :

Qt::DropActions ModeleDispos::supportedDropActions() const{
		return Qt::MoveAction|Qt::CopyAction;
	}

Qt::DropActions ModeleDispos::supportedDropActions() const{
		return Qt::MoveAction|Qt::CopyAction;
	}

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Do you know what could explain that ?

[wysota]

If you just drag an item, it is considered a copy action. To make a move action one has to hold some meta key -- control, alt or shift (I don't remember which) while performing the operation. I think it's possible to force some action but I don't know if it can be done without subclassing the view. Probably it would be easier to emulate a move within one view as a copy and handle it in dropMimeData().

[castorvert]

My solution was the following (I subclassed views) :

void viewSource::mouseMoveEvent(QMouseEvent *event)
{ 
	QModelIndexList liste=selectedIndexes();
	QMimeData *mimeData = model()->mimeData(liste);
	QDrag *drag = new QDrag(this);
	drag->setMimeData(mimeData);
	drag->setHotSpot(event->pos() - rect().topLeft());
	Qt::DropAction dropAction = drag->start( Qt::MoveAction);
	if (dropAction == Qt::MoveAction) {
		model()->removeRows(liste[0].row(),liste.size(),liste[0].parent());
	}
}

void viewSource::mouseMoveEvent(QMouseEvent *event)
{ 
	QModelIndexList liste=selectedIndexes();
	QMimeData *mimeData = model()->mimeData(liste);
	QDrag *drag = new QDrag(this);
	drag->setMimeData(mimeData);
	drag->setHotSpot(event->pos() - rect().topLeft());
	Qt::DropAction dropAction = drag->start( Qt::MoveAction);
	if (dropAction == Qt::MoveAction) {
		model()->removeRows(liste[0].row(),liste.size(),liste[0].parent());
	}
}

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and :

void viewTarget::dropEvent(QDropEvent *e) //viewTarget subclassed QListView
{
	QListView::dropEvent(e);
	e->setDropAction(Qt::MoveAction);
	e->accept();
}

void viewTarget::dropEvent(QDropEvent *e) //viewTarget subclassed QListView
{
	QListView::dropEvent(e);
	e->setDropAction(Qt::MoveAction);
	e->accept();
}

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I think it will remind you sth wysota

Thanks for all

[castorvert]

Well, in fact, my "removeRows" doesn't work because the selected items aren't obligatory following each others.

[wysota]

I think it will remind you sth wysota

Hmm... remind me what?