How do I interact with QML from C++ in QtQuick 2.0

Question

Let’s say that we have a very simple QML file, like this one:

import QtQuick 2.0

Rectangle {
    width: 800
    height: 600
    color: '#000'

    Text {
        text: qsTr("Hi all")
        anchors.centerIn: parent
    }
}

The QML File is loaded with the QtQuick2ApplicationViewer helper class, like this:

QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile(QStringLiteral("qml/MyApp/Login/Window.qml"));
viewer.showFullScreen();

How should I proceed, if for example I would like to change the Rectangle’s color to white, from C++. My guess was:

QQuickItem *window = viewer.rootObject();
window->setProperty("color", "#fff");

But all that does is the following compiler error:

invalid use of incomplete type 'struct QQuickItem'
forward declaration of 'struct QQuickItem'

@LucaCarlon :D Thanks a lot. Never could have thought of it. — Itay Grudev
– Itay Grudev, Commented Dec 2, 2012 at 12:29

Community · Accepted Answer · 2017-05-23 11:56:13Z

6

Then QQuickItem was forward declared somewhere in a header you included, but not fully qualified. Here more information.

edited May 23, 2017 at 11:56

CommunityBot

11 silver badge

answered Dec 2, 2012 at 13:46

Luca Carlon

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Mureinik · Accepted Answer · 2014-02-13 16:18:56Z

2

QObject *rootObject = (QObject *)viewer.rootObject();
rootObject->setProperty("color", "red");

edited Feb 13, 2014 at 16:18

Mureinik

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answered Feb 13, 2014 at 16:00

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