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/*******************************************************************************
 * Copyright (c) 2005, 2009 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     John Cortell, Freescale - bug 289409
 *******************************************************************************/
package org.eclipse.jface.viewers;

/**
 * The ILazyTreeContentProvider is the content provider for tree viewers created
 * using the SWT.VIRTUAL flag that only wish to return their contents as they
 * are queried.
 * 
 * @since 1.0
 */
public interface ILazyTreeContentProvider extends IContentProvider {
	/**
	 * Called when a previously-blank item becomes visible in the TreeViewer. If
	 * the content provider knows the child element for the given parent at this
	 * index, it should respond by calling
	 * {@link TreeViewer#replace(Object, int, Object)}. The content provider
	 * should also update the child count for any replaced element by calling
	 * {@link TreeViewer#setChildCount(Object, int)}. If the given current child
	 * count is already correct, setChildCount does not have to be called since
	 * a call to replace will not change the child count. If the content
	 * provider doesn't know the child count at this point, and can more
	 * efficiently determine if the element has any children, then it can
	 * instead call {@link TreeViewer#setHasChildren(Object, boolean)}.
	 * 
	 * 

* NOTE #updateElement(int index) can be used to determine * selection values. If TableViewer#replace(Object, int) is not called * before returning from this method, selections may have missing or stale * elements. In this situation it is suggested that the selection is asked * for again after replace() has been called. * * @param parent * The parent of the element, or the viewer's input if the * element to update is a root element * @param index * The index of the element to update in the tree */ public void updateElement(Object parent, int index); /** * Called when the TreeViewer needs an up-to-date child count for the given * element, for example from {@link TreeViewer#refresh()} and * {@link TreeViewer#setInput(Object)}. If the content provider knows the * given element, it should respond by calling * {@link TreeViewer#setChildCount(Object, int)}. If the given current * child count is already correct, no action has to be taken by this content * provider. * * @param element * The element for which an up-to-date child count is needed, or * the viewer's input if the number of root elements is requested * @param currentChildCount * The current child count for the element that needs updating */ public void updateChildCount(Object element, int currentChildCount); /** * Returns the parent for the given element, or null * indicating that the parent can't be computed. * In this case the tree-structured viewer can't expand * a given node correctly if requested. * * @param element the element * @return the parent element, or null if it * has none or if the parent cannot be computed */ public Object getParent(Object element); }





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