Cannot get pointer to qml object instance:

[zeroc8]

I'm trying to access an object instance that is created in QML

main.qml:

Window {
        id: mainwindow
        objectName: "MainWindow"
        width: 1280; height: 720
}

main.cpp:

QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));;
QObject* mainWindow = engine.rootContext()->findChild<QObject*>("MainWindow");
if(!mainWindow) throw("cannot find MainWindow");

The returned mainWindow is null, why is that? Any ideas? Thanks.

[p3c0]

Hi @zeroc8 Thats because the Window you are trying to find is itself a root object and not a child. Thus findChild wont work. Use rootObjects() to get the root objects and then get the first item from the list. So the following gives pointer to first window:

QObject* mainWindow = engine.rootObjects().first(); 

[zeroc8]

@p3c0
thanks, works with an instance of a builtin textcontrol. Hoever, when I try this with my own control, I cannot get a hold of it.

qmlRegisterType<MsgCtrol>("MyStuff",1,0,"MsgCtrol");
QObject* msgCtrl = rootObject->findChild<QObject*>("msgctrl");
if(!msgCtrl) throw("cannot find msgctrl");

MsgCtrol {
objectName: "msgctrl"
}

Any idea what's going on here? Thanks.

[p3c0]

@zeroc8 And where is this MsgCtrol instantiated in ? Can you post the code ?

[zeroc8]

MsgCtrol is instantiated in my main.qml file:

Window {
id: mainwindow
width: 1280; height: 720
color: ctrl.background

    MsgCtrol {
        id: ctrl
        objectName: "msgctrl"
        onPlayMsg: Mainjs.playMsg(message);
    }

[p3c0]

@p3c0 Ok this looks good. Now what is rootObject ? QQmlApplicationEngine doesnot have rootObject it has rootObjects( note 's' ). Are you sure you are using QQmlApplicationEngine ?

[zeroc8]

qmlRegisterType<MsgCtrol>("MyStuff",1,0,"MsgCtrol");
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));;

The MsgCtrol gets instanced fine, but I need to hook it up to some additional webhandler, that's whey I wantend to get a hold of the instance from the outside.
The solution that works is to make the webhandler a member of MsgCtrol and hook up the connections there, but that doesn't seem right.

[p3c0]

@zeroc8 Does it work if you have Item instead of Window as root element ?