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
*/
    protected abstract Item[] getItems(Item item);
    /**
     * Returns the item after the given item in the tree, or <code>null</code>
     * if there is no next item.
     * 
     * @param item
     *           the item
     * @param includeChildren
     *           <code>true</code> if the children are considered in
     *           determining which item is next, and <code>false</code> if
     *           subtrees are ignored
     * @return the next item, or <code>null</code> if none
     */
    protected Item getNextItem(Item item, boolean includeChildren) {
        if (item == null) {
            return null;
        }
        if (includeChildren && getExpanded(item)) {
            Item[] children = getItems(item);
            if (children != null && children.length > 0) {
                return children[0];
            }
        }
        
        
        Item parent = getParentItem(item);
        if (parent == null) {
            return null;
        }