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



  • 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)?



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



  • 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?



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



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



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



  • 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:

    1. 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.
    2. 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?



  • 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.



  • 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 ?


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