Signal and Slots

Bhushan_Sure

I am trying to get value in qml but it is not getting......

main.qml

mousearea
{
onClicked: 
{
       gooooo.displaytext();
   }
}

Connections
        {
            target: gooooo
            onComplete:
            {
             console.log(val);
            }
        }

abc.cpp

displaytext()
{
calling java function
}

Jnifunction
{
//the java is returning to JNI function from here i am calling status function
classobject.status(status);
}

void status(Qtsring status)
{
//from here i am emitting signal 
emit complete(status);
}

No errors are coming, everything is running right i have checked each function by writing debug statement, It is emitting also but problem is after emmitting
it is not coming in Connections.

Where i am wrong ?

Nikhilesh N

@Bhushan_Sure
Have you registered the abc class using Q_PROPERTY?

Gojir4

Hi @Bhushan_Sure,

Did you set your gooooo object as a context property of the Qml engine ?

Abc gooooo;
//...
engine.rootContext()->setContextProperty("gooooo", &gooooo);
//...

Bhushan_Sure

@Gojir4 yes , i did that.

Bhushan_Sure

@Nikhilesh-N
No, in abc.cpp ?

Gojir4

@Bhushan_Sure Can we see the definition of the class Abc ? Especially the complete signal ?

Nikhilesh N

@Bhushan_Sure
Yes, you need to have a header file of abc that inherits from QObject. In that class you may create a Q_PROPERTY, and register this class using qmlRegisterType in main.cpp file.
Then you can create an object of abc class on the QML side, where you can catch your signal.

Bhushan_Sure

@Nikhilesh-N ok i will try this.
Could you tell me what will here
Be signal and slot and object
In Q_property syntax ?

Bhushan_Sure

@Gojir4 ok
I will post that class tomorrow as i m out of office now !

Gojir4

@Nikhilesh-N The goal is not to create the object from QML side, as it is "shared" as a QML context property, but only to catch the signal. So, at my opinion, there is no need to use Q_PROPERTY or to register the type at all.

You could make a complete property, and then use the "onCompleteChanged" signal from QML. But why using a property if a signal is enough to notify the QML side ?

dheerendra

@Bhushan_Sure Either you have missed registering the your goose object 'gooooo' before loading the qml. Just check whether you have defined the complete signal. Is it defined with capital letters ? Hope all the methods in abc.cpp are defined with scope resolution.

Nikhilesh N

@Gojir4 If that is the case, your solution of using a context property is good and will suffice.

@Bhushan_Sure If you folow Gojir4's solution, you can emit your signal via C++ and catch it via QML in a Connections object without any issues. Either this, or you also can emit your signal through QML in order to catch it there.

Bhushan_Sure

@Nikhilesh-N @dheerendra @Gojir4
Hi i Solved the problem, From JNI function i was creating new object and then calling function,

Jnifunction
{
//the java is returning to JNI function from here i am calling status function
classobject.status(status);
}

instead of that i used same instance of object and called it and the problem got solved.

dheerendra

It was issue of different objects ?

Bhushan_Sure

@dheerendra yes sir, Sir how to solved this issue if i have to use different object and not the same instance.

dheerendra

practically this case should not arise. If you can show me the simple code sample, I can help you.