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Diffstat (limited to 'java/com/android/contacts/common/Collapser.java')
-rw-r--r-- | java/com/android/contacts/common/Collapser.java | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/java/com/android/contacts/common/Collapser.java b/java/com/android/contacts/common/Collapser.java new file mode 100644 index 000000000..0b5c48bf2 --- /dev/null +++ b/java/com/android/contacts/common/Collapser.java @@ -0,0 +1,95 @@ +/* + * Copyright (C) 2009 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package com.android.contacts.common; + +import android.content.Context; +import java.util.Iterator; +import java.util.List; + +/** + * Class used for collapsing data items into groups of similar items. The data items that should be + * collapsible should implement the Collapsible interface. The class also contains a utility + * function that takes an ArrayList of items and returns a list of the same items collapsed into + * groups. + */ +public final class Collapser { + + /* + * The Collapser uses an n^2 algorithm so we don't want it to run on + * lists beyond a certain size. This specifies the maximum size to collapse. + */ + private static final int MAX_LISTSIZE_TO_COLLAPSE = 20; + + /* + * This utility class cannot be instantiated. + */ + private Collapser() {} + + /** + * Collapses a list of Collapsible items into a list of collapsed items. Items are collapsed if + * {@link Collapsible#shouldCollapseWith(Object)} returns true, and are collapsed through the + * {@Link Collapsible#collapseWith(Object)} function implemented by the data item. + * + * @param list List of Objects of type <T extends Collapsible<T>> to be collapsed. + */ + public static <T extends Collapsible<T>> void collapseList(List<T> list, Context context) { + + int listSize = list.size(); + // The algorithm below is n^2 so don't run on long lists + if (listSize > MAX_LISTSIZE_TO_COLLAPSE) { + return; + } + + for (int i = 0; i < listSize; i++) { + T iItem = list.get(i); + if (iItem != null) { + for (int j = i + 1; j < listSize; j++) { + T jItem = list.get(j); + if (jItem != null) { + if (iItem.shouldCollapseWith(jItem, context)) { + iItem.collapseWith(jItem); + list.set(j, null); + } else if (jItem.shouldCollapseWith(iItem, context)) { + jItem.collapseWith(iItem); + list.set(i, null); + break; + } + } + } + } + } + + // Remove the null items + Iterator<T> itr = list.iterator(); + while (itr.hasNext()) { + if (itr.next() == null) { + itr.remove(); + } + } + } + + /* + * Interface implemented by data types that can be collapsed into groups of similar data. This + * can be used for example to collapse similar contact data items into a single item. + */ + public interface Collapsible<T> { + + void collapseWith(T t); + + boolean shouldCollapseWith(T t, Context context); + } +} |