QML to CPP

eirnanG

Good Day!

How to pass a value or string from QML to CPP.
It is like, when i clicked the MouseArea from QML it will send a number/string to cpp. And cpp will do some calculation.

Please Help.

kamalakshantv

[quote author="eirnanG" date="1309430672"]Good Day!

How to pass a value or string from QML to CPP.
It is like, when i clicked the MouseArea from QML it will send a number/string to cpp. And cpp will do some calculation.

Please Help.[/quote]

Please post it in a single section and "avoid":http://developer.qt.nokia.com/forums/viewthread/7325 multiple posts.

andre

Did you try the "relevant documentation":http://developer.qt.nokia.com/doc/qt-4.7/qml-extending.html ?

eirnanG

its irrelevant i think? or i just dont understand that.

can you cite some sample codes? or situation?

thisisbhaskar

[quote author="QtK" date="1309431176"]
[quote author="eirnanG" date="1309430672"]Good Day!

How to pass a value or string from QML to CPP.
It is like, when i clicked the MouseArea from QML it will send a number/string to cpp. And cpp will do some calculation.

Please Help.[/quote]

Please post it in a single section and "avoid":http://developer.qt.nokia.com/forums/viewthread/7325 multiple posts.
[/quote]

this "avoid" path does not exist.

The link Andre posted has all the required information and has sample code also :).

Basically you create a QObject derived class with a QML callable function ( By placing Q_INVOKABLE before it), and then create an instance of that class inside your c++ code and make the created object available in qml by exporting it with QDeclarativeContext::setContextProperty, and call qml invokable function from QML side when you want to pass data

Example :
C++ Code
@
QmlApplicationViewer viewer;
YourQmlObject qmlobject(&viewer);
QDeclarativeContext * context = viewer.rootContext();
context->setContextProperty("qmlobject",&basicCalc);
@

qml side
@
qmlobject.callFunction("stringyouwanttopass");
@

callFunction is declared and defined in your YourQmlObject class and YourQmlObject is a QObject derived class.

Declaration of callFunction is

@Q_INVOKABLE void callFunction(QString str);@

eirnanG

what are the codes inside the class YourQmlObject?

i think thats what i need but i cant use it well..

thisisbhaskar

Ok.. I would suggest you to visit page
http://developer.qt.nokia.com/wiki/Introduction_to_Qt_Quick_for_Cpp_developers

and then search for "Calling C++ methods from QML", you will get the answer you are looking for :)

eirnanG

i already tried it.. but lack of codes.. like, how can i display it, what are the codes inside the cpp..

please help.. thanks. :)

eirnanG

@Vijay Bhaska Reddy can give me ur email so i can send you the whole codes? to see it personally?

thisisbhaskar

You can copy/paste the code here... others can also have a look and advise you something :) or

you can send the code to my mail id by selecting "Send mail" link in my profile page.

eirnanG

@vijay.. im planning to pass a value from QML when the mousearea is clicked and pass it to CPP to store it..

mousearea>clicked>pass an integer=5>store it in CPP>compute etc... >display in QML.. like that..

thanks

changsheng230

@
// MyItem.qml
import QtQuick 1.0

Item {
width: 100; height: 100

 MouseArea {
     anchors.fill: parent
     onClicked: {
         myObject.cppMethod("Hello from QML")
         myObject.cppSlot(12345)
     }
 }

@

@
// CPP code
class MyClass : public QObject
{
Q_OBJECT
public:
Q_INVOKABLE void cppMethod(const QString &msg;) {
qDebug() << "Called the C++ method with" << msg;
}

public slots:
void cppSlot(int number) {
qDebug() << "Called the C++ slot with" << number;
}
};

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

 QDeclarativeView view;
 MyClass myClass;
 view.rootContext()->setContextProperty("myObject", &myClass;);

 view.setSource(QUrl::fromLocalFile&#40;"MyItem.qml"&#41;&#41;;
 view.show();

 return app.exec&#40;&#41;

}
@

eirnanG

@all thanks to your response..
@changsheng230 thanks! ill try it :)