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
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.events.TreeEvent;
import org.eclipse.swt.events.TreeListener;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Item;
import org.eclipse.swt.widgets.Widget;
/**
 * Abstract base implementation for tree-structure-oriented viewers (trees and
 * table trees).
 * <p>
 * Nodes in the tree can be in either an expanded or a collapsed state,
 * depending on whether the children on a node are visible. This class
 * introduces public methods for controlling the expanding and collapsing of
 * nodes.
 * </p>
 * <p>
 * As of 3.2, AbstractTreeViewer supports multiple equal elements (each with a
 * different parent chain) in the tree. This support requires that clients
 * enable the element map by calling <code>setUseHashLookup(true)</code>.
 * </p>
 * <p>
 * Content providers for abstract tree viewers must implement one of the
 * interfaces <code>ITreeContentProvider</code> or (as of 3.2, to support
 * multiple equal elements) <code>ITreePathContentProvider</code>.
 * </p>
 * 
 * @see TreeViewer
 * @see TableTreeViewer
 */
public abstract class AbstractTreeViewer extends StructuredViewer {