[Qt-qml] QObjectListModel loading time

[Johan Paul]

In general Qt Quick (at least 1) is in general not very good with 
dynamically changing data models in List views.

And in any more complicated cases than showing a few static items in a 
QML List, I would go with exposing a QAbstractListModel to Qt Quick 
instead of the QList<QObject *> approach.

http://doc.qt.nokia.com/latest/qdeclarativemodels.html#qabstractitemmodel

Then, at least in theory, you have the possibility to efficiently change 
the content of your model asynchronously.


Cheers,

Johan


> Hi,
>
> I was previously adding objects one-by-one... I tried updating
> everything at once as you mentioned (ie. with QObjectList) and there was
> no delay at all, which is awesome :)
> However, doing this isn't really ideal in all cases -- for example, if I
> asynchronously receive a bunch of objects I need to update the view
> with, I'm stuck.
>
> Also as an aside (but related question), is using QObjectListModel with
> threading safe? Ie, am I allowed to use it outside of the main thread?
> If you try to move QObjectListModel into its own thread, you need to
> register the QModelIndex object as a metatype, and after doing that,
> things *seemed* to work fine, but I was wondering if anyone had a
> concrete answer.
>
> Regards,
>
> Pris
>
> On Sun, Nov 13, 2011 at 4:05 AM, Andre Somers <andre at familiesomers.nl
> <mailto:andre at familiesomers.nl>> wrote:
>
>     Op 13-11-2011 7:29, Pris Matic schreef:
>      > Hiya,
>      >
>      > I've been using this class:
>      > https://qt.gitorious.org/qt-labs/qml-object-model to expose a list of
>      > QObject properties to a ListView. It works great until the number of
>      > objects in the ListView starts going up. I have about 70 objects
>     in my
>      > list view, each with maybe 10 properties (all QStrings or ints). My
>      > delegate isn't complicated, and ListView performance (ie. scrolling)
>      > is fluid. The issue is it takes forever for the ListView to load in
>      > the first place... upwards of 6-7 seconds on my dual core PC. This
>      > doesn't occur if you expose the data to the ListView through
>      > QVariant... in that case the data shows up almost immediately. Once
>      > the data is loaded, everything runs great. It also loads fine when
>      > there are less than 10-15 items. Has anyone else experienced this
>     when
>      > using a Qaim based model with ListView in QML? Are there any
>     workarounds?
>      >
>     How do you add the QObjects to the QObjectListModel? Do you do that
>     object-by-object, or do you set the whole list in one go using a
>     QObjectList?
>
>     André
>
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