ILazyTreeContentProvider


1   /*******************************************************************************
2    * Copyright (c) 2005, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.jface.viewers;
12  
13  /**
14   * The ILazyTreeContentProvider is the content provider for tree viewers created
15   * using the SWT.VIRTUAL flag that only wish to return their contents as they
16   * are queried.
17   * 
18   * @since 3.2
19   */
20  public interface ILazyTreeContentProvider extends IContentProvider {
21      /**
22       * Called when a previously-blank item becomes visible in the TreeViewer. If
23       * the content provider knows the child element for the given parent at this
24       * index, it should respond by calling
25       * {@link TreeViewer#replace(Object, int, Object)}. The content provider
26       * should also update the child count for any replaced element by calling
27       * {@link TreeViewer#setChildCount(Object, int)}. If the given current child
28       * count is already correct, setChildCount does not have to be called since
29       * a call to replace will not change the child count.
30       * 
31       * <strong>NOTE</strong> #updateElement(int index) can be used to determine
32       * selection values. If TableViewer#replace(Object, int) is not called
33       * before returning from this method, selections may have missing or stale
34       * elements. In this situation it is suggested that the selection is asked
35       * for again after replace() has been called.
36       * 
37       * @param parent
38       *            The parent of the element, or the viewer's input if the
39       *            element to update is a root element
40       * @param index
41       *            The index of the element to update in the tree
42       */
43      public void updateElement(Object   parent, int index);
44  
45      /**
46       * Called when the TreeViewer needs an up-to-date child count for the given
47       * element, for example from {@link TreeViewer#refresh()} and
48       * {@link TreeViewer#setInput(Object)}. If the content provider knows the
49       * given element, it should respond by calling
50       * {@link TreeViewer#setChildCount(Object, int)}. If the given current
51       * child count is already correct, no action has to be taken by this content
52       * provider.
53       * 
54       * @param element
55       *            The element for which an up-to-date child count is needed, or
56       *            the viewer's input if the number of root elements is requested 
57       * @param currentChildCount 
58       *            The current child count for the element that needs updating
59       */
60      public void updateChildCount(Object   element, int currentChildCount);
61      
62      /**
63       * Returns the parent for the given element, or <code>null</code> 
64       * indicating that the parent can't be computed. 
65       * In this case the tree-structured viewer can't expand
66       * a given node correctly if requested.
67       *
68       * @param element the element
69       * @return the parent element, or <code>null</code> if it
70       *   has none or if the parent cannot be computed
71       */
72      public Object   getParent(Object   element);
73  }
74
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