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
* element has been added to the model, in order to cause the viewer to
     * accurately reflect the model. This method only affects the viewer, not
     * the model. Note that there is another method for efficiently processing
     * the simultaneous addition of multiple elements.
     * </p>
     * 
     * @param parentElementOrTreePath
     *           the parent element or path
     * @param childElement
     *           the child element
     */
    public void add(Object parentElementOrTreePath, Object childElement) {
        add(parentElementOrTreePath, new Object[] { childElement });
    }
    /**
     * Adds the given SWT selection listener to the given SWT control.
     * 
     * @param control
     *           the SWT control
     * @param listener
     *           the SWT selection listener
     * @deprecated
     */
    protected void addSelectionListener(Control control,
            SelectionListener listener) {
        
    }
    /**
     * Adds a listener for expand and collapse events in this viewer. Has no
     * effect if an identical listener is already registered.