Bug 138608 [Viewers] JFace AbstractTreeViewer: itemExists doesn't handle equal tree entries
I use a TreeViewer with - setUseHashLookup(true) - without any sorter or filter - with a comparer When I try to add an object that is equal to an existing entry in the tree, it will not be added. This is because the method private boolean itemExists(Item[] items, Object element) { if(usingElementMap()) { return findItem(element) != null; } for (int i = 0; i < items.length; i++) { if(items[i].getData().equals(element)) { return true; } } return false; } takes a shortcut if there is an element map, but the shortcut doesn't handle the 'multiple equal elements' case. There is a workaround, however: Setting a dummy sorter will avoid the call to itemExists and multiple equal elements can be added to the tree.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
}
                Object d = widget.getData();
                if (d != null) {
                    Object parentElement = d;
                    Object[] children;
                    if (isTreePathContentProvider() && widget instanceof Item) {
                    	TreePath path = getTreePathFromItem((Item)widget);
                    	children = getSortedChildren(path);
                    } else {
                    	children = getSortedChildren(parentElement);
                    }
                    for (int i = 0; i < children.length; i++) {
                        createTreeItem(widget, children[i], -1);
                    }
                }
            }
        });
    }
    /**
     * Creates a single item for the given parent and synchronizes it with the
     * given element.
     * 
     * @param parent
     *           the parent widget
     * @param element
     *           the element
     * @param index
     *           if non-negative, indicates the position to insert the item
     *           into its parent
     */