Create QML component from C++. How?

[bogong]

Hello all!

What am I missing? I am trying to create QML dynamically from C++ in following official documentation but got error and QML component do not showing.

main.qml

// Application window
Window {

	property bool isDesktop: GLOBAL.isDesktop();
	property real scaleRate: width/GLOBAL.uiWidth();

	id: applicationWindow;
	visible: true;
	width: isDesktop ? GLOBAL.desktopApplicationWidth() : maximumWidth;
	height: isDesktop ? GLOBAL.desktopApplicationHeight() : maximumHeight;
	title: qsTr("QtQuick Hello World");

	Rectangle {

		id: contentWrapper;
		width: parent.width;
		height: parent.height;
		color: COLOR.white();

		Column {

			id: bottomBlock;
			objectName: "bottomBlock";
			width: parent.width;
			anchors.bottom: parent.bottom;
			spacing: 10;

//			ButtonExit {}

			Item {

				id: paddingButtom;
				width: parent.width;
				height: 30;
			}
		}
	}
}

button.qml

Rectangle {

	id: buttonExit;
	color: "#000000";
	width: parent.width * 0.8;
	height: width * 0.2;
	anchors.horizontalCenter: parent.horizontalCenter;

	Text {

		id: buttonExitLabel;
		text: qsTr("Exit");
		anchors.horizontalCenter: parent.horizontalCenter;
		anchors.verticalCenter: parent.verticalCenter;
		color: "#FFFFFF";
		font.pointSize: 18;
	}

	MouseArea {

		id: buttonExitArea;
		anchors.fill: parent;
		onClicked: {
			Qt.quit();
		}
	}
}

main.cpp

int main(int Counter, char *Arguments[]) {

	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
	QGuiApplication Application(Counter, Arguments);

	QQmlApplicationEngine Engine;
	Engine.load(QUrl(Main));
	if (Engine.rootObjects().isEmpty()) {
		return -1;
	}

	QObject *oRootObject = dynamic_cast<QObject*>(Engine.rootObjects()[0]);
	QObject *oBottomBlock = oRootObject->findChild<QObject*>("bottomBlock");

	QQmlComponent oComponent(&Engine,QUrl(QString("qrc:/ButtonExit.qml")),QQmlComponent::PreferSynchronous);
	QObject *oButtonExit = oComponent.create();
	oButtonExit->setParent(oBottomBlock);

	return Application.exec();
}

When I start it got this error's:

qrc:/ButtonExit.qml:29: TypeError: Cannot read property 'width' of null
qrc:/ButtonExit.qml:31: TypeError: Cannot read property 'horizontalCenter' of null
qrc:/ButtonExit.qml:37: TypeError: Cannot read property 'horizontalCenter' of undefined
qrc:/ButtonExit.qml:38: TypeError: Cannot read property 'verticalCenter' of undefined

It's looks like the Button object do attached to the object but do not see the parent-property in QML. Every property defined through "parent" not working. When I am attaching it directly in QML - everything works fine.

[bogong]

When I am dumping children, the button block attached.

main.cpp

int main(int Counter, char *Arguments[]) {

	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
	QGuiApplication Application(Counter, Arguments);

	QQmlApplicationEngine Engine;
	Engine.load(QUrl(Main));
	if (Engine.rootObjects().isEmpty()) {
		return -1;
	}

	QObject *oRootObject = dynamic_cast<QObject*>(Engine.rootObjects()[0]);
	QObject *oBottomBlock = oRootObject->findChild<QObject*>("bottomBlock");
	
	if (oBottomBlock) {
		QQmlComponent oComponent(&Engine,QUrl(QString("qrc:/ButtonExit.qml")));
		QObject *oButtonExit = oComponent.create();
		oButtonExit->setParent(oBottomBlock);
		aLOG << oBottomBlock;
		aLOG << oBottomBlock->children();
	}

	return Application.exec();
}

the log from application:

qrc:/ButtonExit.qml:30: TypeError: Cannot read property 'width' of null
qrc:/ButtonExit.qml:32: TypeError: Cannot read property 'horizontalCenter' of null
1567240723538 QQuickColumn(0x7f989ec986e0, name = "bottomBlock")
1567240723538 (QQuickItem(0x7f989ec989e0, name = "paddingButtom"), QQuickRectangle(0x7f989ecaa530, name = "buttonExit"))

And I've got another question - How to put created object in defined place? For example if I want to place "buttonExit" before "paddingButtom". For now it's after. I understand that children - it's only QObjectList, but how to make specially defined order of this QObjectList. Is there any way to put child in special place?

[bogong]

Solution found. There are need to be added not like QObject parent, there need to be done like QQuickItem parent. This solution woks for me now:

int main(int Counter, char *Arguments[]) {

	QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
	QGuiApplication Application(Counter, Arguments);

	QQmlApplicationEngine Engine;
	Engine.load(QUrl(Main));
	if (Engine.rootObjects().isEmpty()) {
		return -1;
	}

	QObject *oRootObject = dynamic_cast<QObject*>(Engine.rootObjects()[0]);
	QObject *oBottomBlock = oRootObject->findChild<QObject*>("bottomBlock");

	if (oBottomBlock) {

		QQmlComponent oComponent(&Engine,QUrl(QString("qrc:/ButtonExit.qml")));
		QObject *oButtonExit = oComponent.create();
		QQuickItem *oItemButtonExit = qobject_cast<QQuickItem*>(oButtonExit);
		oItemButtonExit->setParentItem(qobject_cast<QQuickItem*>(oBottomBlock));
	}

	return Application.exec();
}