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
* @see ITreeViewerListener#treeExpanded
     */
    protected void fireTreeExpanded(final TreeExpansionEvent event) {
        Object[] listeners = treeListeners.getListeners();
        for (int i = 0; i < listeners.length; ++i) {
            final ITreeViewerListener l = (ITreeViewerListener) listeners[i];
            SafeRunnable.run(new SafeRunnable() {
                public void run() {
                    l.treeExpanded(event);
                }
            });
        }
    }
    /**
     * Returns the auto-expand level.
     * 
     * @return non-negative level, or <code>ALL_LEVELS</code> if all levels
     *         of the tree are expanded automatically
     * @see #setAutoExpandLevel
     */
    public int getAutoExpandLevel() {
        return expandToLevel;
    }
    /**
     * Returns the SWT child items for the given SWT widget.
     * 
     * @param widget
     *           the widget
     * @return the child items
     */