Retrieve object from QML files other than the main.qml

Synfony

I am building a QtQuick app in which the main.qml file gets loaded as below:
-----main.cpp --------
QApplication app(argc, argv);
QQmlApplicationEngine engine;
……………...
………..
// Load main QML file
engine.load(QUrl("qrc:/resources/main.qml"));
QObject rootObject = engine.rootObjects().first();
m_vtkFboItem = rootObject->findChild<QVTKFramebufferObjectItem>("vtkFboItem");
.……..
app.exec();

Apart from the main.qml file I have another qml file called MyRect.qml.
Here is the main.qml file's content:

ApplicationWindow {
id: root
Rectangle {
id: screenCanvasUI
anchors.fill: parent

    /*MyRect{
        objectName: "rect"
    }*/

    VtkFboItem { //If it stays inside the main.qml file as in here it works!
       objectName: "vtkFboItem"

……………...

}
}
If the VtkFboItem item stays inside the main.qml file as shown above it works fine.
But, if I place the VtkFboItem inside the MyRect.qml I can't locate it from the main.cpp file using the engine.rootObjects().first() method.

Could anybody provide any guideline about how to access QML objects (that resides in QML files other than the main,qml) from C++?

Thanks a lot.

rrlopez

@Synfony That's because when you do engine.rootObjects().first() you get your main.qml object. From main.qml you can only access your MyRect layout. You would have to access your MyRect item and from there access your VtkboItem in order for it to work.

What you can do with this approach is access custom properties defined on the MyRect layout, so i.e. you could make an alias to your VtFboItem on MyRect and then access it with:
QQmlProperty::read(childObject, "someProperty") where childObject is your MyRect item.

ODБOï

hi
@Synfony said in Retrieve object from QML files other than the main.qml:

But, if I place the VtkFboItem inside the MyRect.qml I can't locate it from the main.cpp file using the engine.rootObjects().first() method.

you are loading "main.qml" , so engine.rootObjects().first() references your ApplicationWindow in the main.qml

@Synfony said in Retrieve object from QML files other than the main.qml:

Could anybody provide any guideline about how to access QML objects (that resides in QML files other than the main,qml) from C++?

https://doc.qt.io/qt-5/qtqml-cppintegration-interactqmlfromcpp.html

GrecKo

@Synfony said in Retrieve object from QML files other than the main.qml:

Could anybody provide any guideline about how to access QML objects (that resides in QML files other than the main,qml) from C++?

Don't.

Expose data in C++ and react to it in QML.

Synfony

Dear All,
Many thanks for your responses. It looks like I am trying to access the item in the wrong list. I guess I should explain the issue more clearly. I have two qml files: the main.qml and the MyRect.qml; the contents of each looks as below:
//main.qml file
ApplicationWindow {
id: root
Rectangle {
id: screenCanvasUI
anchors.fill: parent

    MyRect{
        //objectName: "rect"
    }

    
}

}//end:ApplicationWindow

//MyRect.qml file:
Item{
VtkFboItem {
objectName: "vtkFboItem"
anchors.fill: parent

    MouseArea {
	 .............
    }
}//end: VtkFBO

}//end: Item

Now, in order to connect the "vtkFboItem" with C++ code I am using the following code from cpp file:
// Load main QML file
engine.load(QUrl("qrc:/resources/main.qml"));
// Get reference to the QVTKFramebufferObjectItem created in QML
QObject* rootObject = engine.rootObjects()[0];
m_vtkFboItem = rootObject->findChild<QVTKFramebufferObjectItem*>("vtkFboItem");

QObject* rootObject = engine.rootObjects()[0];
m_vtkFboItem = rootObject->findChild<QVTKFramebufferObjectItem*>("vtkFboItem");

if (m_vtkFboItem)
{
m_vtkFboItem->setProcessingEngine(m_processingEngine);
connect(m_vtkFboItem, &QVTKFramebufferObjectItem::rendererInitialized, this, &CanvasHandler::startApplication);
.....................
}
app.exec();

But, it is not working as shown above. If I use "MyRect.qml" in engine.load("MyRect.qml") then the applicatinWindow does not load.
I am not quite sure how should I be able to achieve the connection (as in the code above) using custom property in MyRect.qml.

What should be the standard approach in this case? Perhaps, a few lines of sample code would help!

I appreciate your wise suggestions.
Please help!

ODБOï

@Synfony said in Retrieve object from QML files other than the main.qml:

If I use "MyRect.qml" in engine.load("MyRect.qml") then the applicatinWindow does not load.

why would you do that ? what is your final goal ?

Please try to explain what are you trying to do;
are you trying to :
instanciate a VtkFboItem Qml component in your main.qml inside a Rectangle and access it from your main.cpp ??

Please use Forum "Code </>" tool to past your codes with correct formatting

Synfony

ApplicationWindow {
id: root
Rectangle {
id: screenCanvasUI
anchors.fill: parent
   Drawer{
      ……..
   }
   MyRect{  }   
 
}
}//end:ApplicationWindow

Synfony

@LeLev
In the main.qml file I have navigation elements (e.g. Drawer) and other UI elements (e.g. tabs, splitter etc.) and inside the main.qml I need to display MyRect.qml (it holds the VtkFboItem).
I also need to connect the VtkFboItem with the C++ object to display AND interact with 3D graphics.

ApplicationWindow {
  id: root
  Rectangle {
     id: screenCanvasUI
     anchors.fill: parent
     Drawer{
      ……..
     }
      MyRect{  }   
 
    }
    Button {
            id: openFileButton
            text: "Add Model"
        …………...
    }
   FileDialog {.....}
}//end:ApplicationWindow

/MyRect.qml file:
Item{
      VtkFboItem {
           objectName: "vtkFboItem"
          anchors.fill: parent
            MouseArea {
	 .............
          }
       }//end: VtkFBO
      
}//end: Item

//main.cpp file
.......
// Load main QML file
engine.load(QUrl("qrc:/resources/main.qml"));
// Get reference to the QVTKFramebufferObjectItem created in QML
QObject* rootObject = engine.rootObjects()[0];
m_vtkFboItem = rootObject->findChild<QVTKFramebufferObjectItem*>("vtkFboItem");
QObject* rootObject = engine.rootObjects()[0];
m_vtkFboItem = rootObject->findChild<QVTKFramebufferObjectItem*>("vtkFboItem");
if (m_vtkFboItem)
{
     m_vtkFboItem->setProcessingEngine(m_processingEngine);
     connect(m_vtkFboItem,           &QVTKFramebufferObjectItem::rendererInitialized, this, &CanvasHandler::startApplication);
.....................
}
app.exec();

In the above scenario, how should I be able to find and connect to the vtkFboItem from the main.cpp?

Is there any other way to achieve this apart from the objectName?
I have attached here a screenshot of the final UI that I am trying to achieve.