After implementing this, i noticed that with the FilteredTree a
selection of a checkbox does not cause the checkboxes of the item's
children be selected IF the item is not expanded AND was not expanded
before. Only if the particular treeitem was expanded manually(!!)
before, also the checkboxes of the item's children are selected.
I debugged through the code and found out that the getItems() method of
the FilteredTree's Tree causes the problem. After starting the
Application the getItem() method returns only items for items that are
expanded originally. I also tried to expand and collapse all items
before the application starts, but no success. After expanding and
collapsing all items the traversal of the items worked fine, but after
starting the application the traversal was only possible for expanded items.
So, is there a way to traverse all the TreeItems of a FilteredTree, no
matter if the items are expanded/has been expanded before?