use c++ Listmodel object in qml

hasson

recently,I wrote a class inherites from QAbstractListModel called listModel, I wanna use this model in qml, and I have registered it in main.c by setContextProperty function. The first running it worked well, but when listModel's data changed, the app showed a "segment fault".
in main.c
QQmlApplicationEngine engine;
QQmlComponent component(&engine, QUrl(QStringLiteral("qrc:/Main.qml")));
QObject* object = component.create();
app.setObjectInstance(object);

engine.rootContext()->setContextProperty("screenModel",
                                 &ScreenListModel::getInstance());

...
in my qml file
GridView {
anchors.centerIn: parent
width: 300
height: 70
model: screenModel
delegate: UserButton {
nameCn: model.name_cn
nameEn: model.name_en
}
}

hasson

I guess I have found the issue, because the function where operate QAbstractListModel is in a normal thread , when used a signal/slot ,the app works well.
thank you all~

jsulm

@hasson Please show your code, else others can only guess...

hasson

code is update , could you help me pls, when GridView is not defined ,it works well

jsulm

@hasson said in use c++ Listmodel object in qml:

The first running it worked well, but when listModel's data changed, the app showed a "segment fault".

Did you run your app through debugger?
Do so and take a look at the stack trace (you can post it here, so others can check).
How do you change listModel data?
What do you do in ScreenListModel?

hasson

@jsulm said in use c++ Listmodel object in qml:

What do you do in ScreenListModel?
thanks,
I insert model item by this way:
QList<ScreenInfo> m_list;
void ScreenListModel::insert(int index, const ScreenInfo &si)
{
if(index < 0 || index > m_list.count()) {
return;
}
emit beginInsertRows(QModelIndex(), index, index);
m_list.insert(index, si);
emit endInsertRows();
}

the app is running on arm board so i can't see the stack trace,but the problem is occured while inserting a item,the operation is on a thread ,ScreenListModel is a singleton

IntruderExcluder

beginInsertRows and endInsertRows are not signals, they should not be emitted.

hasson

thanks, i found it got crashed when i inserted item in another thread, but it works well in main thread

GrecKo

@IntruderExcluder said in use c++ Listmodel object in qml:

beginInsertRows and endInsertRows are not signals, they should not be emitted.

While true, this won't change anything since emit just expands to nothing. emit x = x.
It's better for others reading your code though.

hasson

I guess I have found the issue, because the function where operate QAbstractListModel is in a normal thread , when used a signal/slot ,the app works well.
thank you all~