Qt/QML - Registering a QML type in C++ makes QML code not work

Question

I am working on something where I have a class called "FloatingMenu" (that is supossed to manage a menu in C++) and its QML alter-ego for the GUI in a file FloatingMenu.qml. I have a file main.qml where I have a few rectangles and a FloatingMenu, and it shows up as expected. Now, if I do qmlRegisterType("EasyGraph", 1,0, "FloatingMenu"); in my main.cpp, the graphical part of the FloatingMenu juts desappears.

Here is my code:

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

 QGuiApplication app(argc, argv);

 //Register all the needed types in QML.
 qmlRegisterType<FloatingMenu>("EasyGraph", 1,0, "FloatingMenu");


 //The only window known as QDeCView in QML.
 QQuickView* view = new QQuickView();
 view->setMinimumHeight(100);
 view->setMinimumWidth(100);
 view->setResizeMode(QQuickView::SizeRootObjectToView);

 //Context, to set properties from c++ to QML
 //QQmlContext* cxt =  view->rootContext();

 //Load the base.
 view->setSource(QUrl::fromLocalFile("../qml/MainWindow.qml"&#41;&#41;;
 view->show();

 //FloatingMenu* menu = view->rootObject()->findChild<FloatingMenu*>("mainMenu"); //When registered, this works

 return app.exec();
}

and:

#ifndef _FLOATINGMENU_H_
#define _FLOATINGMENU_H_

#include <QQuickItem>
#include "GraphicalNode.hpp"


class FloatingMenu : public QQuickItem {
 Q_OBJECT
 Q_PROPERTY(GraphicalNode* target READ target WRITE setTarget NOTIFY onTargetNodeChanged)
private:
 GraphicalNode* _target;
public:
 FloatingMenu(QQuickItem* p = NULL);
 GraphicalNode* target() const;
 void setTarget(GraphicalNode* n);

signals:
 void onTargetNodeChanged(GraphicalNode*);
};


#endif

#include "FloatingMenu.hpp"

FloatingMenu::FloatingMenu(QQuickItem* p) : QQuickItem(p), _target(NULL){
 setFlag(QQuickItem::ItemHasContents, false); //I tried true and false here. what should it be? It has content, but I don't want to draw it from the C++ side.
}


GraphicalNode* FloatingMenu::target() const {
 return _target;
}

void FloatingMenu::setTarget(GraphicalNode* n) {
 _target = n;
}

my MainWindow.qml:

import EasyGraph 1.0
import QtQuick 2.0



Rectangle {
 width: 400; height: 400
 color: "#333333"

 Flickable {
  id: flickable
  anchors.fill: parent
  width: 400; height: 400

  FloatingMenu{
   objectName: "mainMenu"
   id: menu
  }



 }

}

and finally, FloatingMenu.qml:

import EasyGraph 1.0
import QtQuick 2.0

Rectangle {
 width: 30; height: 30
 color: "red"
}

I have no idea what I am doing wrong, I dont see how its not working. The only thing I want to do is to bind a QML object with a class and let the QML be the drawing part... I guess I am missing a little option or something that would make it work.

Thanks in advance!

Answer 1

When you import your module EasyGraph you hide your file FloatingMenu.qml. Change it to SomeFloatingMenu.qml and use your FloatingMenu item:

import EasyGraph 1.0 
import QtQuick 2.0 
FloatingMenu {
    Rectangle { width: 30; height: 30 color: "red" }
}

Now use your SomeFloatingMenu, it is your c++ class created within qml component:

import QtQuick 2.0 
Rectangle { 
    width: 400; height: 400; color: "#333333" 
    Flickable { 
        id: flickable; anchors.fill: parent; width: 400; height: 400; 
        SomeFloatingMenu { objectName: "mainMenu"; id: menu } 
    }
}

Answer 2

You have FloatingMenu C++ component and the FolatingMenu.qml , which also is a Component. So when you write FloatingMenu{} in some qml file where you import EasyGraph 1.0 , this c++ qml component is found and used.