[Qt-qml] Model view example showing editing capability

[Tim O'Callaghan]

On 01/17/2011 08:04 AM, bea.lam at nokia.com wrote:
> You can find an example of using QAbstractListModel with QML under examples/declarative/modelviews/abstractitemmodel. The example is also online at http://doc.qt.nokia.com/4.7-snapshot/declarative-modelviews-abstractitemmodel.html.
>
> The example doesn't modify the model from QML, but you could for example add a method to the model class like this:
>
> 	Q_INVOKABLE void updateModel(int index, const QVariant&value);
>
> and then you can call this from QML to modify the model data.
>
> The example shows some of the signals that needs to be emitted from a Qt model in order to update the view (e.g. QAbstractItemModel::beginInsertRows() ). If you are simply changing the data in an existing row, then emit dataChanged(). See http://doc.qt.nokia.com/4.7-snapshot/model-view-programming.html#model-subclassing-reference.
>


I've been playing with this example, to try adding a thread that 
randomly adds new items to an Abstract model, using a separate thread.

It seems the abstractmodel+QML cannot cope with updating. I'm hoping its 
something wrong with the model implementation, i guess it needs to send 
a dataChanged signal or something? The error it generates when 
attempting to add the second new item is:

QObject::connect: Cannot queue arguments of type 'QModelIndex'
(Make sure 'QModelIndex' is registered using qRegisterMetaType().)

How do i fix this?

The changed main.cpp is attached, the rest of the source for the example 
is here:
http://qt.gitorious.org/qt/qt/trees/4.7/examples/declarative/modelviews/abstractitemmodel

regards,

Tim.

>
> regards,
>
> Bea
>
>
> On 15/01/2011, at 6:38 PM, ext Pelle Johnsen wrote:
>
>> Hi,
>>
>> I can recommend subclassing QAbstractListModel (http://doc.trolltech.com/4.7/qabstractlistmodel.html). You can use a normal QList, but it only has a single change signal, so if e.g. you insert an item then QML thinks the whole list has changed, which can cause performance problems. The whole Qt model/view classes are rather complex (compared to QList), but in my experience it's worth the effort to use it.
>>
>>   -pjoe
>>
>> On Fri, Jan 14, 2011 at 6:26 PM, Jamil Naja<jamil.m.naja at gmail.com>  wrote:
>> Hi guys,
>> As the title suggests, I am looking for an example with a C++ model and QML view where the QML view (or other QML elements within the QML code) doing modification on the c++ model data.
>>
>> Any suggestions ?
>>
>> Thanks
>> Jamil
>>
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