How to catch a signal emitted from cpp class in Qml ?

[Jagh]

You are sending signal way too early, before there was any chance for a connection to be established. In constructor the object hasn't been fully initialized yet, in particular, the QML-interpreter hadn't had a chance to initialize the object's properties from QML side yet.

[Naveen_D]

@Jagh Okay...
then when should i emit a signal...so that i can catch over there...calling my function in constructor is the mistake...??

[Jagh]

I changed your code a bit so that handleSubmitTextField() is called in more appropriate time(actually i just added a Button and called this function in onClicked handler), and the signal handler was successfully called.

To when: anytime between QML object initialization (implement Component.onCompleted if you want to catch it) and object destruction is ok.

[Naveen_D]

@Jagh can you please post the code so that i will get a clear picture of what i need to do...thanks...

[Naveen_D]

@Jagh I tried the way u told by adding a button and calling the handler...it worked thanks...\o/

[Jagh]

And if you really want to execute some code as soon as possible and have a guarantee that a QML object was fully initialized by the time your code is running, do it in Component.onCompleted handler of that object.

[Naveen_D]

Ok thanks... i will try that also...:-)

[Naveen_D]

Hi i have doubt regarding catching a signal emitted from c++ file
if there are more than 2 .qml files does it catch the signal ?
for ex, i have one .cpp and 4 .qml such as mainform.qml,radio.qml,music.qml,setting .qml
so if i emit a signal and try to catch it in setting.qml does it work ??

[VincentLiu]

@Naveen_D
Yes it works. I have tried before.

[Naveen_D]

@VincentLiu but in my case it is not working....

my code is...
this .cpp where i am emitting signal..

if(!WordList.isEmpty())
            {
                WordList.removeFirst();
                WordList.removeLast();
//                QMessageBox m_popupmsgbox;
//                m_popupmsgbox.setWindowTitle("Voice Recognizer");
//                Phoneme=WordList.join(" ");
//                qDebug()<<"firstword"<<Phoneme<<endl;
//                QSpacerItem* horizontalSpacer = new QSpacerItem(500, 100, QSizePolicy::Minimum, QSizePolicy::Expanding);
//                m_popupmsgbox.setText( Phoneme);
//                QGridLayout* layout = (QGridLayout*)m_popupmsgbox.layout();
//                layout->addItem(horizontalSpacer, layout->rowCount(), 0, 1, layout->columnCount());
//                m_popupmsgbox.exec();
//                emitSignalFunc();
//                m_emitSignal= new EmitSignalClass;
//                m_emitSignal->emitSignalmethod();
                VoiceRecognition voice;
                voice.playmusicsignal();
            }
            else
            {
                qDebug()<<"List is empty"<<endl;
            }

my .qml is

Rectangle{
            id:voicerecRect
            width: settings_main_rect.width/5
            height: settings_main_rect.height/4
            color: "transparent"

            VoiceRecognition {
                id: voiceRecognizer
                onPlaymusicsignal: {
                    console.log("Signal catched...")
                }
            }

            Image {
                id: vr_image
                source: "qrc:/AppbarIcon.png"
                //source: "qrc:/Voice-Recoder-icon.png"
                width: parent.width-10
                height: parent.height-10
                smooth: true
                fillMode: Image.PreserveAspectFit
                anchors.centerIn: parent

                Text {
                    id: vrtext
                    anchors.top: parent.bottom
                    anchors.horizontalCenter: vr_image.horizontalCenter
                    text: qsTr("Voice Recorder")
                    color: "white"
                    font.pixelSize: parent.height * (2 / 9)

                }
                MouseArea {
                    anchors.fill: parent
                    onClicked: {
                        //popup.open()
                        voicerecRect.color = 'green'
                        voiceRecognizer.vstartVoiceRecognition()
                    }
                }
            }
        }
    }

i have registered the class using qmlregister and i am using signal handler to catch the signal...

[VincentLiu]

@Naveen_D
Hi, first of all, I should say that I use different ways to do this. However, according to some similar experience on it. I guess you shouldn't use a new VoiceRecognition object in your .cpp file. I don't think distinct object derived from the same class can communicate this way. Please correct me if I am wrong. Thanks

[Naveen_D]

@VincentLiu the function in which i am emitting a signal is a global function so i need to create an obj of that class and emit.

[Naveen_D]

@VincentLiu what are the different ways...?

[Naveen_D]

Hello, can anyone please help me out with this...
thanks