从 QQuickView 对象设置 QML 项的父属性

Question

I have 3 files (along with CMakeLists.txt and qrc ):

• main.cpp - C++
• BDialog.qml - a "base" for my dialog (contains the property definition)
• BEditorDialog.qml - a dialog with a label

They contain:

// main.cpp

#include <QApplication>
#include <QQuickView>
#include <QQmlContext>


int main( int argc, char **argv )
{
    QApplication app( argc, argv );

    QQuickView view;
    view.rootContext()->setContextProperty( "myText", "WOW!" ); // expected to work but doesn't

    view.setSource( QUrl( "qrc:/BEditorDialog.qml" ) );

    view.show();
    return app.exec();
}

---

//BDialog.qml

import QtQuick 2.6
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

Item {
    // This property I want to set from C++
    property string myText
}

---

// BEditorDialog.qml

import QtQuick 2.6
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

BDialog {
    id: root

    Label {
        id: label
        text: root.myText // doesn't work
    }
}

If I assign initial value to the myText property:

property string myText: "MEH!"

this initial value is displayed, but how to assign it from C++? I suspect I should use the setInitialProperties member function, but I have only Qt 5.12 installed.

Thank you in advance.

Answer 1

You've mixed up context and object. You're setting the property "myText" on the QQmlContext which is not the root object of your application. To get the root object you can use rootObject() on your QQuickView and get a QQuickItem back. On that you can call setProperty() .

This works

#include <QApplication>
#include <QQmlContext>
#include <QQuickItem>
#include <QQuickView>

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    QQuickView view;
    view.setSource(QUrl("qrc:/BEditorDialog.qml"));
    // First set the source and then access the rootObject, otherwise it isn't create yet
    view.rootObject()->setProperty("myText", "WOW!");

    view.show();
    return app.exec();
}

Answer 2

In addition to the answer of iam_peter, you can actually also use the context property in the way you have set it, but with the warning that a name collision is present. This might be more appropriate in bigger projects (it seems here you only want a way to show a dialog from C++ and be done with it)

Given a proper name, say 'myDialogText', you can use it as follows:

// BEditorDialog.qml

import QtQuick 2.6
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3

BDialog {
    id: root

    Label {
        id: label
        text: myDialogText
    }
}