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Java > Open Source Codes > org > eclipse > jface > viewers > ILazyTreePathContentProvider


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 ILazyTreePathContentProvider is a tree path-based content provider for
15  * tree viewers created using the SWT.VIRTUAL flag that only wish to return
16  * their contents as they are queried.
17  *
18  * @since 3.3
19  */
20 public interface ILazyTreePathContentProvider 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 parentPath
38      * The tree path of parent of the element, or if the
39      * element to update is a root element, an empty tree path
40      * @param index
41      * The index of the element to update in the tree
42      */
43     public void updateElement(TreePath parentPath, int index);
44
45     /**
46      * Called when the TreeViewer needs an up-to-date child count for the given
47      * tree path, for example from {@link TreeViewer#refresh()} and
48      * {@link TreeViewer#setInput(Object)}. If the content provider knows the
49      * element at the given tree path, 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 treePath
55      * The tree path for which an up-to-date child count is needed, or
56      * if the number of root elements is requested, the empty tree path
57      * @param currentChildCount
58      * The current child count for the element that needs updating
59      */
60     public void updateChildCount(TreePath treePath, int currentChildCount);
61     
62     /**
63      * Called when the TreeViewer needs up-to-date information whether the node
64      * at the given tree path can be expanded. If the content provider knows the
65      * element at the given tree path, it should respond by calling
66      * {@link TreeViewer#setHasChildren(Object, boolean)}. The content provider
67      * may also choose to call {@link TreeViewer#setChildCount(Object, int)}
68      * instead if it knows the number of children.
69      *
70      * <p>
71      * Intended as an optimization for when the viewer does not need the actual
72      * children. Clients may be able to implement this more efficiently than
73      * <code>updateChildCount</code>.
74      * </p>
75      *
76      * @param path
77      * The tree path for which up-to-date information about children
78      * is needed
79      */
80     public void updateHasChildren(TreePath path);
81
82     /**
83      * Return the possible parent paths for the given element. An empty array
84      * can be returned if the paths cannot be computed. In this case the
85      * tree-structured viewer can't expand a given node correctly if requested.
86      * If the element is a potential child of the input of the viewer, an empty
87      * tree path should be an entry in the returned array.
88      *
89      * @param element
90      * the element
91      * @return the possible parent paths for the given element
92      */
93     public TreePath[] getParents(Object JavaDoc element);
94 }
95
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