[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&#40;"qml/NativeInteg/BaseDialog.qml"&#41;&#41;;
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&#40;"qml/Example/main.qml"&#41;);

QDeclarativeComponent* component = new QDeclarativeComponent(m_view.engine(), QUrl::fromLocalFile&#40;"qml/Example/QML1.qml"&#41;);
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