[SOLVED] ListView drag and drop, data model exposed from C++

borut123

Hi

This is a great example of how to implement drag and drop in QML:
http://developer.qt.nokia.com/wiki/Drag_and_Drop_within_a_GridView

Would it be also possible to implement similar feature if I use the data model exposed from C++
( context->setContextProperty("listItems", QVariant::fromValue(listItems)) ),
and not the data model defined in QML (via ListModel)?

DenisKormalev

Yes. You need to implement some methods marked as Q_INVOKABLE to move elements, but I'm sure it not too difficult.

borut123

Ok, but if you look at the example code, "icons.move(newIndex, newIndex = index, 1)" is used in QML javascript.

icons is defined as: " model: WidgetModel { id: icons }"

in my case I'm using model exposed from C++, so it's: "model: myModel"

And there I can not use QML javascript code "myModel.move() to move the item", or maybe I can?

DenisKormalev

you can use "myModel.move()" from js if you have move() method marked as Q_INVOKABLE or slot.

borut123

Thanks, after implementing list model from QAbstractListModel, and of course also move() method, everything works fine.

DenisKormalev

Don't forget to mark your own threads which you think are solved with "[solved]" in title.

carlossst

Hello!

I got exactly the same issue as borut123, and from your explanations I understand:
To be able to use myModel.move() in QML I need to implement in C++ move() by using Q_INVOKABLE.

But:

After reading QML and C++ documentation, Q_INVOKABLE is needed to create NEW methods in C++ (not previously existing in QML), then make them visible to QML and next use them in QML.
move() method is a property ALREADY defined in QML as ListModel::move ( int from, int to, int n ).

The question is:
how exactly I have to use Q_INVOKABLE with move() to enable usage of myModel.move() in QML? Because I should need to declare in the C++ model class? Then: Is it needed to reimplement move() in .cpp also?

borut123

You need to implement QAbstractListModel, and then send the instance of this model to QML.

C++ header file code snippet:

@class YourObject : public QAbstractListModel {

Q_OBJECT

public:
int rowCount(const QModelIndex & parent = QModelIndex()) const;
Q_INVOKABLE void move(int from, int to, int count);
Q_INVOKABLE YourObject* get(int i) const;
QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;

@
I hope this helps you a little bit.

jackyang

Hi borut123,

I saw you reimplement "get" function of model in c++ header file.

Does its return value YourObject is your model's pointer?

Should it be the pointer of item which model stored, not model's ?