[solved] QObject::findChild() not working for QML Items inside Window

m_andrej

Hello,

I need to get a pointer to one of my QML elements from my C++ code, which should be possible with findChild() (see http://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html)

However, it just doesn't work. When I get the top-level item from window->contentItem() and call findChild(), it keeps returning zero pointer.

My main.cpp:

#include <QGuiApplication>
#include <QQuickWindow>
#include <QQuickItem>
#include <QtQml>
#include <QTimer>
#include <QtDebug>

void checkItem(QQmlApplicationEngine *pEngine);

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

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    QTimer::singleShot(2000, [&]() {
        checkItem(&engine);
    });

    return app.exec();
}

void checkItem(QQmlApplicationEngine *pEngine) {
    QQuickWindow *window = qobject_cast<QQuickWindow *>(pEngine->rootObjects().first());
    QQuickItem *topItem = window->contentItem();
    qDebug() << "topItem: " << topItem;

    QQuickItem *rect = topItem->findChild<QQuickItem *>("myItem");
    qDebug() << "rect: " << rect;
}

My main.qml:

import QtQuick 2.5
import QtQuick.Window 2.2

Window {
    visible: true

    Rectangle {
        width: 100
        height: 100
        color: "lightblue"
        objectName: "myItem"

        Text {
            text: qsTr("Hello world!")
            anchors.centerIn: parent
        }
    }
}

Output of the program:

topItem:  QQuickRootItem(0x1e929b0, parent=0x0, geometry=0,0 160x160)
rect:  QQuickItem(0)

Of course I also tested whether topItem isn't the rectangle itself, but topItem->objectName() prints just empty string.
Any ideas?

m_andrej

I got it working by not searching among children of topItem, but of window:

QQuickItem *rect = window->findChild<QQuickItem *>("myItem");

I find it astonishing, because window->contentItem() should return the root item of the scene. So my light blue rectangle should definitely be one of its children.