[Qt-jambi-interest] Displaying the hierarchical structure of an xml file using model/view framework

[Gunnar Sletta]

moebius at altern.org wrote:
> Hello,
> 
> I'm trying to write a small app for displaying the hierarchical structure
> of an xml file using the model/view framework.
> 
> To do this, I have created a XmlTreeModel class inherited from
> QAbstractItemModel to hold the hierarchical model and a QTreeView to
> display it. I have also defined a XmlTreeItem class to handle each single
> xml element.
> Parsing file and building model is achieved in populate(), parseBranch()
> and createItem() functions. For each XmlTreeItem instance, the
> corresponding QModelIndex.internalId is the reference identifier. This
> Long value is stored into the XmlTreeItem instance itself and also into a
> HashMap<Long, XmlTreeItem>. This unique identifier for each XmlTreeItem
> instance is used to retrieve data once the model completely built,
> especially in the QAbstractModelItem data() function.
> 
> Here is the model class code (quite long, sorry) :

Hi,

The QAbstractItemModel is not an ideal class for representing 
hierarchical datastructures, unfortunatly. There was quite some 
discussion about this in the early days of this mailing list and I did 
post an example in this thread:

http://lists.trolltech.com/qt-jambi-interest/2006-12/thread00011-0.html

It uses the same approach as you, with an internalId-index hash and is 
quite slow because of it ;-/

I didn't look thouroughly at your code, but I suggest that you look at 
your parent() function. That is usually where I usually have problem in 
the QAbstractItemModel.

Because of the lack of usability and some performance problems with 
QAbstractItemModel in Java when used as a QTreeModel we implemented 
com.trolltech.qt.gui.QTreeModel. Did you look at it? With it you can map 
your XMLNodes directly rather than using the QModelIndex indirection.

Hope this helps,

Gunnar