ubuntu-phone team mailing list archive

[James Henstridge <james.henstridge@xxxxxxxxxxxxx>]

On 17 June 2016 at 20:58, Matthias Apitz <guru@xxxxxxxxxxx> wrote:
>
> Hello,
>
> I'm trying to write my first QML/C++ app, so please be patient with me
> :-)
>
> The C++ main.cpp has:
>
> ...
> int main(int argc, char *argv[]) {
>   QGuiApplication app(argc, argv);
>   QQuickView v;
>   QUrl file = (QUrl) "myRoot/home/phablet/baresip-app/baresip.qml";
>
>   v.setSource(file);
>   v.show();
>
>   MyClass myClass;
>
>   QObject *item = v.rootObject();
>   QObject *newButton = item->findChild<QObject*>("dialButton");
>   QObject::connect(newButton, SIGNAL(qmlSignal(QString)),
>                      &myClass, SLOT(cppSlot(QString)));
>
>   return app.exec();
> }
>
> and the QML object is:
>
> import QtQuick 2.4
> import Ubuntu.Components 1.3
>
>
> MainView {
>
>     Rectangle {
>         id: page
>         width: 540; height: 960
>         color: "lightgray"
>         border.color: "grey"
>         border.width: 5
>         radius: 10
>
>         Text {
>             id: baresipTitle
>             ...
>         }
>
>         ...
>
>     Item {
>         id: dialButton
>         x: 10
>         y: 110
>         property alias cellColor: rectangle.color
>         property alias cellText: buttonText.text
>
>         signal qmlSignal(string msg)
>
>         width: 160; height: 50
>
>         Rectangle {
>             id: rectangle
>             border.color: "blue"
>             color: "lightgrey"
>
>             anchors.fill: parent
>
>             Text {
>                 id: buttonText
>                 text: "Dial"
>                 x: 8
>                 y: 24
>                 font.pointSize: 12
>             }
>         }
>
>         MouseArea {
>             anchors.fill: parent
>             hoverEnabled: true
>             onEntered: rectangle.border.color = "blue"
>             onExited:  rectangle.border.color = "green"
>
>             onClicked: button.qmlSignal("Hello from QML")
>         }
>
>         cellColor: buttonMouseArea.pressed ? Qt.darker(buttonColor, 1.5) : buttonColor
>     }
>     ...
> }
>
> The app starts fine but the C++ part does not find the "dialButton", it
> says:
>
> Loading module: 'libubuntu_application_api_touch_mirclient.so.3.0.0'
> QObject::connect: Cannot connect (null)::qmlSignal(QString) to MyClass::cppSlot(QString)
>
> Sure, that I do something wrong, but what?
>
> Thanks for any help or pointer to help. The full project sources are
> attached.

When combining C++ and QML, it is usually easiest to connect
everything up from the QML side.  You can register your class with QML
by adding the following statement on the C++ side:

   qmlRegisterType<MyClass>("somemodule", 1, 0, "MyClass");

Now on the QML side, "import somemodule 1.0" will allow you to create
instances of MyClass.  Any Q_PROPERTY declarations will be accessible
on the class, and any slots or methods marked with Q_INVOKABLE will be
callable from QML.  Now you should be able to hook up the signal just
as you would for any other QML component.

James.