[solved] QML dynamic object creation in C++

[omersaleem]

Hi, I'm just out on QML and am looking for some assistance in the following...

I'm trying to dynamically create a QML object from C++ and do this without using any of the QGraphics* classes. As QGraphicsView is the current backend and will be removed I wanted to stick to using QDeclarative* classes only.

Dynamic object creation from QML works using...
@
myDialog = Qt.createComponent("BaseDialog.qml").createObject(baseObj);
@

Dynamic object creation from C++ using QGraphicsView works using...
@
QDeclarativeEngine* engine = m_view.engine();
QDeclarativeContext* context = engine->rootContext();
QObject* rootObj = context->findChild<QObject*>("baseObj");
QDeclarativeItem rootitem = qobject_cast<QDeclarativeItem>(rootObj);

QDeclarativeComponent component(engine, QUrl::fromLocalFile("qml/NativeInteg/BaseDialog.qml"));
QObject *myObject = component.create();
QDeclarativeItem *item = qobject_cast<QDeclarativeItem*>(myObject);

item->setParentItem(rootitem);
m_view.scene()->addItem(item);

@

But using pure QDeclarative* classes I can't seem to achieve it, so far I have...
@
QDeclarativeContext* context = m_view.engine()->rootContext();
QDeclarativeComponent* component = new QDeclarativeComponent(m_view.engine(), QUrl::fromLocalFile("qml/NativeInteg/BaseDialog.qml"), m_view.engine());
QDeclarativeItem* myDialog = qobject_cast<QDeclarativeItem*>(component->create());

QObject* child = context->findChild<QObject*>("baseObj");
QDeclarativeItem *rootitem = qobject_cast<QDeclarativeItem*>(child);
myDialog->setParentItem(rootitem);

@

The component.onCompleted gets fired but nothing is displayed.

Any ideas on what I need to do next?

Thanks in advanced.

Omer

[thisisbhaskar]

what is "baseObj", is it the objectName of your root qml component??

[omersaleem]

Yeah, sorry about the naming, still in prototyping phase. 'baseObj' is the name of the root element that I have loaded by my main.qml. It is intended to be the parent of the object that I trying to dynamically create.

[thisisbhaskar]

then the below code seems to work
@int main(int argc, char *argv[])
{
QApplication app(argc, argv);

QDeclarativeView m_view;// =  new QDeclarativeView();
m_view.setSource(QUrl::fromLocalFile("qml/Example/main.qml"));

QDeclarativeComponent* component = new QDeclarativeComponent(m_view.engine(), QUrl::fromLocalFile("qml/Example/QML1.qml"));
QDeclarativeItem* myDialog = qobject_cast<QDeclarativeItem*>(component->create());

myDialog->setParentItem(qobject_cast<QDeclarativeItem*>(m_view.rootObject()));
m_view.showFullScreen();

return app.exec();

}
@

[omersaleem]

Ok cool, that works. The only thing is rootObject() in line 11 returns a QGraphicsObject so presumably this method will be removed/changed when the backend is migrated from QGraphicsView to Scene Graph?

[thisisbhaskar]

so, I guess so and mark the thread as solved by appending (Solved) to the title of the thread.

[nidhi.sharma]

hello,

I have an application, in which i am using the same approach.
now if i want to access the properties of baseObj, which meant to be parent of my dynamically created object, what should i do.

Here is example of my code..

main.qml
import FirstButtonClick 1.0
Rectangle{
property string myString : "My String"
Text{
text : "main file"
}
MouseArea{
onClicked:{
buttonClick.openPage("qrc:qml/FirstButton.qml")
}
}

   FirstButtonClick{
          id : buttonClick
   }

}

FirstButton.qml
Rectangle{
Text{
text : "FirstButton Page"
}

    Component.onCompleted{
                console.log("main.qml property : " + myString // main.qml property)
     }

}

main.cpp
#include "FirstButtonClick.h"
#include "main.h"

int main(int argc, char *argv[])
{
qmlRegisterType<>("FirstButtonClick", 1, 0, "FirstButtonClick");

    QApplication app(argc, argv);     
    m_view =  new QDeclarativeView;
    m_view.setSource(QUrl("qrc:qml/main.qml"));
    m_view.showFullScreen();     
    return app.exec();

}

main.h
QDeclarativeView* m_view;

FirstButtonClick.h
extern QDeclarativeView* m_view;
class FirstButtonClick : public OQbject
{
Q_OBJECT;
public :
Q_INVOKABLE QObject* openPage(QString fileName);
}

FirstButtonClick.cpp
#include "FirstButtonClick.h"

QObject* FirstButtonClick :: openPage(QString fileName)
{
QDeclarativeContext* context = m_view->engine()->rootContext();
QDeclarativeComponent* component = new QDeclarativeComponent(m_view->engine(), QUrl(fileName), m_view->engine());

     QObject * object = component->create();
     QDeclarativeItem* myDialog = qobject_cast<QDeclarativeItem*>(object); 

      QDeclarativeItem *rootitem = qobject_cast<QDeclarativeItem*>(m_view->rootObject());
      myDialog->setParentItem(rootitem);

      return object;

}

the problem with the above code is FirstButton.qml page is loaded but when it tries to access the property of main.qml ie. myString it cant access it.

suggest me me a way to use it properly