keyeventfilter place create object

Damian7546

Hi,

I use keyeventfilter to read code scanner. I have a little problem with my project architecture. Below it is my main.cpp:

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    
     MyKeyEventFilter myKeyEventFilter;
    app.installEventFilter(&myKeyEventFilter);

    //QML
    qmlRegisterType< SystemController >  ("MyController",1,0,"SystemController");

    QQmlApplicationEngine engine;

    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);
    return app.exec();
}

The SystemController I used to exchange data beetwen my logic and QML.

Is it possible use installEventFilter inside SystemController and events would be works on whole application ? Thanks this, the signal from MyKeyEventFilter I would connect to slot in other object created inside System Controller. now is impossible, i am right ?

I try liake below:


SystemController::SystemController(QObject *parent)
    : QObject{parent}
{

    MyKeyEventFilter myKeyEventFilter;
    this->installEventFilter(&myKeyEventFilter);
}

and I removed form main.cpp, but in this way events doesn't work....

Damian7546

@SGaist The MyKeyEventFilter works all the time when app is turn.
I solved my problem by integrate QML with qt by:

engine.rootContext()->setContextProperty("myobject", myobject);

SGaist

Hi,

What is the lifetime of MyKeyEventFilter in SystemController's constructor ?

Damian7546

@SGaist The MyKeyEventFilter works all the time when app is turn.
I solved my problem by integrate QML with qt by:

engine.rootContext()->setContextProperty("myobject", myobject);

JoeCFD

@Damian7546 you may pay more attention to what SGaist said. Try to use more heap space(pointers), especially Qt items or classes.
this kind of definition MyKeyEventFilter myKeyEventFilter; can be fatal in your app sometimes.
Try to use pointer: auto myKeyEventFilter = new MyKeyEventFilter;

Damian7546

@JoeCFD said in keyeventfilter place create object:

this kind of definition MyKeyEventFilter myKeyEventFilter; can be fatal in your app sometimes.

I would be really grateful if you could explain me why ?