Qml with C++ extensions

[gunturrohith]

Hi i am new to QML and trying to run a small QML program using c++ extension in Qt-5.4.0

here is my code app.qml

import QtQuick 2.1
import QtQuick.Controls 1.0
 
Button {
       id: generate
       text: qsTr("&Generate")
       onClicked: generate.btn_clicked()
     }

import QtQuick 2.1
import QtQuick.Controls 1.0

Button {
       id: generate
       text: qsTr("&Generate")
       onClicked: generate.btn_clicked()
     }

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button.h

#ifndef BUTTON_H
#define BUTTON_H
 
#include <QDeclarativeItem>
#include <QObject>
#include <QDebug>
#include <QWidget>
 
class BButton : public QWidget
{
        Q_OBJECT
 
public:
        BButton();
 
        Q_INVOKABLE void btn_clicked();
 
};
#endif

#ifndef BUTTON_H
#define BUTTON_H

#include <QDeclarativeItem>
#include <QObject>
#include <QDebug>
#include <QWidget>

class BButton : public QWidget
{
        Q_OBJECT
        
public:
        BButton();

        Q_INVOKABLE void btn_clicked();
        
};
#endif

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button .cpp

#include "button.h"
 
BButton::BButton()
{
//nothing to write
 
}
void BButton::btn_clicked()
{
        qDebug("THE GUI was clicked");
}

#include "button.h"

BButton::BButton()
{
//nothing to write

}
void BButton::btn_clicked()
{
        qDebug("THE GUI was clicked");
}

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main.cpp

#include "button.h"
#include <qdeclarative.h>
#include <QDeclarativeView>
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    //qmlRegisterType<PieChart>("Charts", 1, 0, "PieChart");
 
    QDeclarativeView view;
    view.setSource(QUrl::fromLocalFile("app.qml"));
    view.show();
    return app.exec();
}

#include "button.h"
#include <qdeclarative.h>
#include <QDeclarativeView>
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    //qmlRegisterType<PieChart>("Charts", 1, 0, "PieChart");

    QDeclarativeView view;
    view.setSource(QUrl::fromLocalFile("app.qml"));
    view.show();
    return app.exec();
}

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While executing using qmlscene the GUI was creating fine but on clicking the button it is showing the following error

file:///root/Btn_Sig/app.qml:7: TypeError: Property 'btn_clicked' of object Button_QMLTYPE_35(0x161c950) is not a function

Please tell me is there anything more to add in my code to generate the output or did i miss something.

Thanks in advance,
Rohith.G

[anda_skoa]

There's a couple of things:

- Your QML code import QtQuick.Controls, which has a Button type, which is what your QML is instantiating. QtQuick.Controls.Button doesn't have the method you are trying to call
- QDeclarativeView is for QtQuick 1, you need QQuickView for QtQuick 2
- Your button class is a QtWidget, you can't incorporate a widget in a QtQuick 2 scene
- Your button class is not registered with the QML type system

Cheers,
_

[gunturrohith]

HI anda_skoa,

Thanks for replying to execute my program successfully which class should i use instead of QWidget,
Please tell me and if possible can you please post the code that helps to execute my program.

Thanks in advance,
Rohith.G

[anda_skoa]

Thanks for replying to execute my program successfully which class should i use instead of QWidget,

Depends on what you want to do.
QObject could be fine if you only need some methods exported.

Please tell me and if possible can you please post the code that helps to execute my program.

I haven't tried executing your program, these findings are purely from looking at the code you've posted.

Cheers,
_

[gunturrohith]

Hi anda_skoa,

I just need a program to create a button in qml and when i click on the button it should print the qDebug that was present in the slot of C++.

I am trying to learn how to connect Qml and C++ by using signal and slots that is what my intention.

Thanks in advance,
Rohith.G

[anda_skoa]

There are a couple of options to do something like that.

The easiest way is to create an instance of a QObject derived class in C++ and use QQmlContext::setContextProperty() to make that instance accessible from QML.
The context itself can be retrieved from the QQmlEngine of the QQuickView.

Cheers,
_