[Solved] Can't dynamically add and display objects to QML from C++ (Qt 5.02)

blazern

Hi all,

I've been trying to learn how to dynamically add objects to QML from C++ code, but all the code I write doesn't work.

I want to add an object defined in Unit.qml to the application's window (defined in generated file main.qml).

I created a new Qt Quick 2 application (by Create Project --> Applications --> Qt Quick 2 Application (Built-in Elements)), added a method for creating QML objects in class QtQuick2ApplicationViewer (the class was generated by Qt Creator), and called this method from main().

Then tried to follow "this ":http://qt-project.org/doc/qt-5.0/qtqml/qtqml-cppintegration-interactqmlfromcpp.html article, so the method I added to QtQuick2ApplicationViewer looked like this:

@void QtQuick2ApplicationViewer::addQmlObject()
{
QQmlComponent * component = new QQmlComponent(this->engine(), QUrl::fromLocalFile("Unit.qml"), this);

QObject * object = component->create();

}@

Here's Unit.qml code:

@import QtQuick 2.0

Item {
id: unit
width: 40
height: 40

Image {
    id: image
    width: parent.width
    height: parent.height
    anchors.fill: parent
    source: "content/unit.png"
}

}@

And it doesn't work. Probably the problem is in my misunderstanding of QML-C++ interacting, but I can't figure out what's wrong.
Could anyone help me, please?

sierdzio

In order to be shown, the object needs to have a parent. Otherwise QML engine does not know where to draw it.

This is how I do it in CCF:
@
// constructor of my hybrid C++/QML item:
mEffectsComponent = new QQmlComponent(mMainInstance->engine(),
QUrl::fromLocalFile("qml/effects/Effect.qml"));

// item creation code, in another function:
QObject *CcfQmlBaseScenario::createEffect(QObject *parent)
{
if (mEffectsComponent->isReady()) {
QObject *object = mEffectsComponent->create();
object->set("parent", QVariant::fromValue(parent));
return object;
} else {
return 0;
}
}
@

It's not exactly the same situation you're having, but maybe the snippet will help you. This is the whole code, if you need it: "link":https://github.com/sierdzio/closecombatfree/blob/master/src/qmlBase/ccfqmlbasescenario.cpp#L30.

blazern

sierdzio, It works! Thank you sooo much!

I only had to add the next line to the end of my addQmlObject() method:

@object->setProperty("parent", QVariant::fromValue(this->rootObject()));@

The problem is solved.

sierdzio

Cool :) Please prepend "[Solved]" to the topic's title (you need to edit your first post too do that), it might help some other bloke in need ;)