[Qt-qml] Problem with finding qml elements placed within ListView delegate from C++ code

[Дмитрий Шаховский]

>
>
> 11 июля 2011 г. 7:06 пользователь <bea.lam at nokia.com> написал:

>
> On 08/07/2011, at 4:19 AM, ext Дмитрий Шаховский wrote:
>
> > Hi,
> > I have a problem when I tried to find a qml element placed within
> ListView delegate from C++ code.
> >
> > E.g.
> >
> > Rectangle {
> >    ...
> >    ListView{
> >        ...
> >        delegate: Rectangle{
> >                      objectName: "rect"
> >                  }
> >
> >        model: ListModel{
> >                   ListElement{}
> >                   ListElement{}
> >                   ListElement{}
> >               }
> >    }
> > }
> >
> > And somewhere in C++ code
> >
> > QDeclarativeView *view = new QDeclarativeView;
> > view->setSource(QUrl::fromLocalFile("myqmlfile.qml"));
> > QObject* rootObject = view->rootObject();
> > QObject* obj = rootObject->findChild<QObject*>("rect");
> >
> > obj will be null.
>
>
> QObject::findChild() won't find the delegate objects because they are added
> as "child items" in the graphics scene, rather than child objects in the
> QObject* hierarchy. Child items in a graphics scene are accessible through
> QGraphicsItem::childItems().
>
> Also, ListView inherits from Flickable, and delegate items within a
> Flickable are parented to a separate item that holds the contents of the
> Flickable, rather than the Flickable itself. This separate item is
> accessible through the 'contentItem' property:
> http://doc.qt.nokia.com/4.7/qml-flickable.html#contentItem-prop
>
> So to find a delegate instance within the view, add an objectName to the
> view:
>
>
> ListView {
>        objectName: "view"
>
>
> and in main.cpp:
>
>    QObject *listView = rootObject->findChild<QObject*>("view");
>    QDeclarativeItem *contentItem =
> qvariant_cast<QDeclarativeItem*>(listView->property("contentItem"));
>
>    foreach (QGraphicsItem *item, contentItem->childItems()) {
>        if (qobject_cast<QDeclarativeItem*>(item)->objectName() == "rect") {
>            qDebug() << "Found:" << item;
>         }
>    }
>
> >
> > in C++ slot connected to rectClicked signal
> >
> > void SomeObject::onRectClicked(QVariant element)
> > {
> >    QObject* rootObject = declarativeView->rootObject();
> >    QObject* listView = rootObject->findChild<QObject*>("listView");
> >
> >    QObject* obj = element.value<QObject*>()->parent()->parent();
> >    //obj will be null instead of the equality of listView
> >    //(element.value<QObject*>() is QDeclarativeRectangle)
> > }
> >
> > So delegate component children are not in root object's tree.
>
> Yes, calling QObject::parent() here is referring to the QObject* parent,
> rather than the parent item in the graphics scene. In QML, referring to
> item.parent actually refers to the QDeclarativeItem* parent item, not the
> QObject* parent (as you can see by the QDeclarativeItem::parent docs).
>
>
> regards,
>
> Bea
>
>
Thanks
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