SetContextProperty multiple files

neovius

Hello,

I have a ReferenceError in my qml file : ReferenceError: userInterface is not defined. The error is in this line:

userInterface.backlightChanged(backlightslider.value)

but the qml link is working properly. below my code

main.cpp

 QGuiApplication app(argc,argv);
    QQmlEngine engine;
    QQmlComponent component(&engine,QUrl("qrc:/QML/Qml/newMain.qml"));
    QObject *object = component.create();
    if (component.isError())
    {
        qDebug() << component.errors();
    }
    UserInterface userInterface(*object);
    engine.rootContext()->setContextProperty("userInterface",&userInterface);
    return app.exec();

newMain.qml

ApplicationWindow {
    id: mainWindow
    width: 1024
    height: 768
    visible: true

    SettingsMenu{ id: settingsMenu; objectName: "SettingsMenu"}

...some more code

settingsMenu

Window {
    id: settingsMenu
    width: 1024
    height: 768
    color: "#d1d3d4"
    visible: false

Slider {
        property bool stateVisible: false
        id: backlightslider
        x: 885
        y: 525
        width: 50
        height: 227
        onValueChanged: {
            userInterface.backlightChanged(backlightslider.value)
        }

userinterface.cpp

UserInterface::UserInterface(QObject &windowInstance)
    :m_object(&windowInstance)
{
    QQuickWindow *item = qobject_cast<QQuickWindow*>(m_object);
    m_playButton = (item->findChild<QObject *>("PlayButton"));
}

void UserInterface::backlightChanged(const int &backlightLevel)
{
    QFile backlight("/sys/class/backlight/backlight_lvds.29/brightness");
    backlight.open(QIODevice::WriteOnly | QIODevice::Truncate);
    QTextStream out(&backlight);
    out << backlightLevel;
    backlight.close();

}

When i change the backlight slider, the signal is emitted, and received. but i still get the warning when starting the application :

ReferenceError: userInterface is not defined

What am i doing wrong?

p3c0

Hi @neovius and Welcome,

When i change the backlight slider, the signal is emitted, and received. but i still get the warning when starting the application :

That is because you are creating QML component before setting the context property and thus naturally it wont be able to access that method at very first time.

http://doc.qt.io/qt-5/qtqml-cppintegration-exposecppattributes.html#exposing-properties
http://doc.qt.io/qt-5/qtqml-cppintegration-exposecppattributes.html#exposing-methods-including-qt-slots