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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of 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,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.contacts.common.list;
     18 
     19 import android.text.TextUtils;
     20 import android.widget.SectionIndexer;
     21 import java.util.Arrays;
     22 
     23 /**
     24  * A section indexer that is configured with precomputed section titles and their respective counts.
     25  */
     26 public class ContactsSectionIndexer implements SectionIndexer {
     27 
     28   private static final String BLANK_HEADER_STRING = " ";
     29   private String[] mSections;
     30   private int[] mPositions;
     31   private int mCount;
     32 
     33   /**
     34    * Constructor.
     35    *
     36    * @param sections a non-null array
     37    * @param counts a non-null array of the same size as <code>sections</code>
     38    */
     39   public ContactsSectionIndexer(String[] sections, int[] counts) {
     40     if (sections == null || counts == null) {
     41       throw new NullPointerException();
     42     }
     43 
     44     if (sections.length != counts.length) {
     45       throw new IllegalArgumentException(
     46           "The sections and counts arrays must have the same length");
     47     }
     48 
     49     // TODO process sections/counts based on current locale and/or specific section titles
     50 
     51     this.mSections = sections;
     52     mPositions = new int[counts.length];
     53     int position = 0;
     54     for (int i = 0; i < counts.length; i++) {
     55       if (TextUtils.isEmpty(mSections[i])) {
     56         mSections[i] = BLANK_HEADER_STRING;
     57       } else if (!mSections[i].equals(BLANK_HEADER_STRING)) {
     58         mSections[i] = mSections[i].trim();
     59       }
     60 
     61       mPositions[i] = position;
     62       position += counts[i];
     63     }
     64     mCount = position;
     65   }
     66 
     67   public Object[] getSections() {
     68     return mSections;
     69   }
     70 
     71   public int getPositionForSection(int section) {
     72     if (section < 0 || section >= mSections.length) {
     73       return -1;
     74     }
     75 
     76     return mPositions[section];
     77   }
     78 
     79   public int getSectionForPosition(int position) {
     80     if (position < 0 || position >= mCount) {
     81       return -1;
     82     }
     83 
     84     int index = Arrays.binarySearch(mPositions, position);
     85 
     86     /*
     87      * Consider this example: section positions are 0, 3, 5; the supplied
     88      * position is 4. The section corresponding to position 4 starts at
     89      * position 3, so the expected return value is 1. Binary search will not
     90      * find 4 in the array and thus will return -insertPosition-1, i.e. -3.
     91      * To get from that number to the expected value of 1 we need to negate
     92      * and subtract 2.
     93      */
     94     return index >= 0 ? index : -index - 2;
     95   }
     96 
     97   public void setProfileAndFavoritesHeader(String header, int numberOfItemsToAdd) {
     98     if (mSections != null) {
     99       // Don't do anything if the header is already set properly.
    100       if (mSections.length > 0 && header.equals(mSections[0])) {
    101         return;
    102       }
    103 
    104       // Since the section indexer isn't aware of the profile at the top, we need to add a
    105       // special section at the top for it and shift everything else down.
    106       String[] tempSections = new String[mSections.length + 1];
    107       int[] tempPositions = new int[mPositions.length + 1];
    108       tempSections[0] = header;
    109       tempPositions[0] = 0;
    110       for (int i = 1; i <= mPositions.length; i++) {
    111         tempSections[i] = mSections[i - 1];
    112         tempPositions[i] = mPositions[i - 1] + numberOfItemsToAdd;
    113       }
    114       mSections = tempSections;
    115       mPositions = tempPositions;
    116       mCount = mCount + numberOfItemsToAdd;
    117     }
    118   }
    119 }
    120