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Java > Open Source Codes > com > google > gwt > user > client > ui > WidgetIterators


1 /*
2  * Copyright 2007 Google Inc.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5  * use this file except in compliance with the License. You may obtain a copy of
6  * the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13  * License for the specific language governing permissions and limitations under
14  * the License.
15  */
16 package com.google.gwt.user.client.ui;
17
18 import java.util.Iterator JavaDoc;
19 import java.util.NoSuchElementException JavaDoc;
20
21 /**
22  * A collection of convenience factories for creating iterators for widgets.
23  * This mostly helps developers support {@link HasWidgets} without having to
24  * implement their own {@link Iterator}.
25  */
26 class WidgetIterators {
27
28   private static final Widget[] copyWidgetArray(final Widget[] widgets) {
29     final Widget[] clone = new Widget[widgets.length];
30     for (int i = 0; i < widgets.length; i++) {
31       clone[i] = widgets[i];
32     }
33     return clone;
34   }
35
36   /**
37    * Wraps an array of widgets to be returned during iteration.
38    * <code>null</code> is allowed in the array and will be skipped during
39    * iteration.
40    *
41    * @param container the container of the widgets in <code>contained</code>
42    * @param contained the array of widgets
43    * @return the iterator
44    */
45   static final Iterator JavaDoc createWidgetIterator(final HasWidgets container,
46       final Widget[] contained) {
47     return new Iterator JavaDoc() {
48       int index = -1, last = -1;
49       boolean widgetsWasCopied = false;
50       Widget[] widgets = contained;
51
52       {
53         gotoNextIndex();
54       }
55
56       private void gotoNextIndex() {
57         ++index;
58         while (index < contained.length) {
59           if (contained[index] != null) {
60             return;
61           }
62           ++index;
63         }
64       }
65
66       public boolean hasNext() {
67         return (index < contained.length);
68       }
69
70       public Object JavaDoc next() {
71         if (!hasNext()) {
72           throw new NoSuchElementException JavaDoc();
73         }
74         last = index;
75         final Widget w = contained[index];
76         gotoNextIndex();
77         return w;
78       }
79
80       public void remove() {
81         if (last < 0) {
82           throw new IllegalStateException JavaDoc();
83         }
84
85         if (!widgetsWasCopied) {
86           widgets = copyWidgetArray(widgets);
87           widgetsWasCopied = true;
88         }
89
90         container.remove(contained[last]);
91         last = -1;
92       }
93     };
94   }
95
96   private WidgetIterators() {
97     // Not instantiable.
98 }
99 }
100
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