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Is there a good reason for having multiple models ? If I was you, I would use a single model and apply the changes inside the same model. But, if you want to keep multiple models, then look at the following functions :

• bool QTreeView::isExpanded ( const QModelIndex & index ) const
  
• void QTreeView::setExpanded ( const QModelIndex & index, bool expanded )
  

Looking at the tree view's source code, I see that the expanded states are saved inside the tree view itself, using a QList container :


Basically, when an item is expanded, its index is added to that expandedIndexes list. When an item is collapsed, its index is removed from that list. Now, the tree view declares this list private -- you cannot access it directly. Your only access functions are those I gave you before : isExpanded() and setExpanded().

And inside setModel(), there's the following instruction :


I see two solutions to your problem :

A/ When unsetting a model, create by your own a list of expanded indexes using isExpanded() and later apply it using setExpanded(). The restore code should start with setUpdatesEnabled(false) and end with setUpdatesEnabled(true).

or

B/ Create as many tree views as tree models.