ViewerFilter


1   /*******************************************************************************
2    * Copyright (c) 2000, 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  import java.util.ArrayList  ;
14  
15  /**
16   * A viewer filter is used by a structured viewer to
17   * extract a subset of elements provided by its content provider.
18   * <p>
19   * Subclasses must implement the <code>select</code> method
20   * and may implement the <code>isFilterProperty</code> method.
21   * </p>
22   * @see IStructuredContentProvider
23   * @see StructuredViewer
24   */
25  public abstract class ViewerFilter {
26      /**
27       * Creates a new viewer filter.
28       */
29      protected ViewerFilter() {
30      }
31  
32      /**
33       * Filters the given elements for the given viewer.
34       * The input array is not modified.
35       * <p>
36       * The default implementation of this method calls 
37       * <code>select</code> on each element in the array, 
38       * and returns only those elements for which <code>select</code>
39       * returns <code>true</code>.
40       * </p>
41       * @param viewer the viewer
42       * @param parent the parent element
43       * @param elements the elements to filter
44       * @return the filtered elements
45       */
46      public Object  [] filter(Viewer viewer, Object   parent, Object  [] elements) {
47          int size = elements.length;
48          ArrayList   out = new ArrayList  (size);
49          for (int i = 0; i < size; ++i) {
50              Object   element = elements[i];
51              if (select(viewer, parent, element)) {
52                  out.add(element);
53              }
54          }
55          return out.toArray();
56      }
57  
58      /**
59       * Filters the given elements for the given viewer.
60       * The input array is not modified.
61       * <p>
62       * The default implementation of this method calls 
63       * {@link #filter(Viewer, Object, Object[])} with the 
64       * parent from the path. Subclasses may override
65       * </p>
66       * @param viewer the viewer
67       * @param parentPath the path of the parent element
68       * @param elements the elements to filter
69       * @return the filtered elements
70       * @since 3.2
71       */
72      public Object  [] filter(Viewer viewer, TreePath parentPath, Object  [] elements) {
73          return filter(viewer, parentPath.getLastSegment(), elements);
74      }
75      
76      /**
77       * Returns whether this viewer filter would be affected 
78       * by a change to the given property of the given element.
79       * <p>
80       * The default implementation of this method returns <code>false</code>.
81       * Subclasses should reimplement.
82       * </p>
83       *
84       * @param element the element
85       * @param property the property
86       * @return <code>true</code> if the filtering would be affected,
87       *    and <code>false</code> if it would be unaffected
88       */
89      public boolean isFilterProperty(Object   element, String   property) {
90          return false;
91      }
92  
93      /**
94       * Returns whether the given element makes it through this filter.
95       *
96       * @param viewer the viewer
97       * @param parentElement the parent element
98       * @param element the element
99       * @return <code>true</code> if element is included in the
100      *   filtered set, and <code>false</code> if excluded
101      */
102     public abstract boolean select(Viewer viewer, Object   parentElement,
103             Object   element);
104 }
105
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