//--- main.cpp
QDeclarativeView *mainView = new QDeclarativeView();
mainView->setSource(QUrl("qrc:/qml/MainWindow.qml"));
QObject *object = mHomeView->rootObject();
QObject *listView = object->findChild<QObject*>("root");

//--- MainWindow.qml
Rectangle {
    id: root
       
    Image {
        id: main
        objectName: "root"
        }
}

 QObject *listView = object->findChild<QObject*>("root");