Retrieve center of QML map in C++ - c++

Question

I've the following QML that shows a map:
import QtQuick 2.0
import QtQuick.Window 2.14
import QtPositioning 5.15
import QtLocation 5
Item {
width: Qt.platform.os == "android" ? Screen.width : 512
height: Qt.platform.os == "android" ? Screen.height : 512
visible: true
property double center_latitude: 59.91
property double center_longitude: 10.75
Plugin {
id: mapPlugin
name: "osm"
}
Map {
anchors.fill: parent
plugin: mapPlugin
center: QtPositioning.coordinate(center_latitude, center_longitude)
zoomLevel: 14
copyrightsVisible: false
}
}
I set int in a QQuickWidget and everything seems ok:
m_quickWidget->setSource(QUrl(QStringLiteral("qrc:/qml/map.qml")));
I can see the map correctly. Now I want to retrieve the coordinates of the center of the map, that should be retrieved with the map center property. The problem is that I don't know how to access to that property with C++.
I've tried
auto mp = m_quickWidget->rootObject()->findChild<QQuickItem*>("Map");
auto items = m_quickWidget->rootObject()->childItems();
auto center = mp->property("center").value<QGeoCoordinate>();
extent.setCenter(LLA{ center.latitude(), center. Longitude(), 0.0 });
center = m_quickWidget->rootObject()->property("center").value<QGeoCoordinate>();
but mp gives me a nullptr, while items is a vector of only one element, and I don't know how to handle it. The last row gives me a QGeoCoordiante with NaN, so it's not correct.
How can I retrieve the center from the QQuickWidget?

Answer 1

findChild() is searching for items via the objectName. So you need to add an objectName to your Map.
Map {
objectName: "testmap"
center: QtPositioning.coordinate(59.91, 10.75)
...
}
and then you can search for it.
auto map = view->rootObject()->findChild<QQuickItem *>("testmap");
if (map) {
auto center = map->property("center").value<QGeoCoordinate>();
qDebug() << map << center;
}
The above code returns the following.
QDeclarativeGeoMap(0x55fc0d7de000, name="testmap", parent=0x55fc0d746940, geometry=0,0 800x600)
QGeoCoordinate(59.91, 10.75)