CODEWITHSUNDEEP
c++qtqmlqtquick2
Ed Nio
Ed Nio

Reputation: 593

cpp Qt Model not updating QML view

I am using a custom model for my QML view and I want to be able to move items thanks to a drag and drop. I use a list in my cpp model to set Data and then I just bind my model to the QML view.

However, when I drop an item in a new position, the view ask the model to move the item on is new position. In that purpose, I just update my dataList with the function dataList.move(oldIndexPosition, newIndexPosition). My dataList is correctly updated but it doesn't refresh the QML view. I tried to use the signal emit dataChanged()but it is still not refreshing the view.

I don't understand what should I do, any suggestion ?

Here is a simple example of what I try to do. Notice that there is no drag and drop here, in order to make it easier to understand:

public:
    Q_INVOKABLE void move(int oldIndex, int newIndex) {
              dataList.move(oldIndex,newIndex);
              emit dataChanged(this->index(oldIndex),this->index(newIndex));
    }

signals:
    void dataChanged(const QModelIndex & topLeft, const QModelIndex & bottomRight);

model.h

int main(int argc, char ** argv)
{
    QGuiApplication app(argc, argv);

    Model model;
    model.addSomeData("data1");
    model.addSomeData("data2");
    model.addSomeData("data3");

    QQuickView view;
    view.setResizeMode(QQuickView::SizeRootObjectToView);
    QQmlContext *ctxt = view.rootContext();
    ctxt->setContextProperty("myModel", &model);

    view.setSource(QUrl("qrc:view.qml"));
    view.show();

    return app.exec();
}

main.cpp

ListView {
    width: 200; height: 250

    model: myModel
    delegate: Text { text: "data " + data  }

    MouseArea {
        anchors.fill: parent
        cursorShape: Qt.PointingHandCursor
        onClicked: {
            myModel.move(0,2) //Just a test
        }
    }
}

myqml.qml

If you have any idea of what I am doing wrong, that would be really kind of you to help me! Thank you very much.

Upvotes: 1

Views: 1505

Answers (1)

m7913d
m7913d

Reputation: 11054

I assume Model is an implementation of QAbstractItemModel. In that case, you should call QAbstractItemModel::beginMoveRows before you start moving your data and QAbstractItemModel::endMoveRows to finalise it.

Q_INVOKABLE void move(int oldIndex, int newIndex) {
    QModelIndex parent;
    beginMoveRows(parent, oldIndex, oldIndex, parent, newIndex);
    dataList.move(oldIndex,newIndex);
    endMoveRows();
}

Upvotes: 4

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