Qt5将QWidget与QtQuick2一起使用

Question

There are a few problems with the combination of Qt5 and QtQuick2. Whenever you would like to use some of the many QWidget based classes you first run across the following problem:

You should be using QApplication instead of Qt5's QGuiApplication . Well that can be easly changed, right?

So now I am using QApplication but whenever I try to use a QWidget based class my program either crashes or results in some nonsense error messages.

How should I use the old QWidgets with Qt5 then? I know that they are not the best solution with Qt5 but they are quite useful...

PS I am developing my app in Linux, for all platforms.
I am also using the auto-generated QtQuick2ApplicationViewer class to render out QtQuick 2.0 based applications.

Answer 1

In Qt 5.1 (and presumably from now on) you should use QWidget::createWindowContainer. Your application should be a QWidget based application and put the QML inside QWidgets. Putting QWidgets into a QML application is not supported.See this blog entry .

If you have a form class and you want to put qml into the container widget.

If you have this QML:

import QtQuick 2.0

Rectangle {
    property alias text: textItem.text
    width: 156
    height: 35
    Text {
        width: 150
        height: 20
        text: qsTr("Hello World")
        id: textItem
    }
}

In a file called myqml.qml, then put the path to it in to the qml prefix of a resource file.

Then put in the form constructor:

ui->setupUi(this); // as normal
QQuickView* view = new QQuickView();
QWidget* widget = QWidget::createWindowContainer(view, ui->container);
view->setSource(QUrl("qrc:/qml/myqml.qml"));
if(view->status()!=QQuickView::Ready)
    qDebug("can't initialise view");
widget->setMinimumSize(500,100);
QQuickItem* container = view->rootObject();

Then when you want to interact with the QML:

container->setProperty("text", "Hello alternate universe");

Answer 2

It seems this is a known bug: https://bugreports.qt.io/browse/QTBUG-25643

That also seems to have links to possible solutions/workarounds, but I did not check them.

About QWidgets and "they are not the best solution": First of all, until future Qt 5.1 (or which ever version it will be) with complete desktop Qt Quick components, they're the only sensible option for regular desktop apps, and only option is by definition best option ;)

But even in future QWidgets are 100% valid choice for a Qt5 app. Only thing with them is, they're unlikely to develop much, so what you have now, is the best you're going to ever have with them. If that's fine, then they're the solution to choose.