package cn.sinata.xldutils.widget;
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import android.widget.SectionIndexer;
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import java.util.Arrays;
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public class CustomSectionIndexer implements SectionIndexer {
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private final String[] mSections;//
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private final int[] mPositions;
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private final int mCount;
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/**
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* @param sections
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* @param counts
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*/
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public CustomSectionIndexer(String[] sections, int[] counts) {
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if (sections == null || counts == null) {
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throw new NullPointerException();
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}
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if (sections.length != counts.length) {
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throw new IllegalArgumentException(
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"The sections and counts arrays must have the same length");
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}
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this.mSections = sections;
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mPositions = new int[counts.length];
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int position = 0;
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for (int i = 0; i < counts.length; i++) {
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if(mSections[i] == null) {
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mSections[i] = "";
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} else {
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mSections[i] = mSections[i].trim();
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}
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mPositions[i] = position;
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position += counts[i];
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}
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mCount = position;
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}
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@Override
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public Object[] getSections() {
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// TODO Auto-generated method stub
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return mSections;
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}
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@Override
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public int getPositionForSection(int section) {
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//change by lcq 2012-10-12 section > mSections.length以为>=
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if (section < 0 || section >= mSections.length) {
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return -1;
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}
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return mPositions[section];
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}
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@Override
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public int getSectionForPosition(int position) {
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if (position < 0 || position >= mCount) {
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return -1;
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}
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//注意这个方法的返回值，它就是index<0时，返回-index-2的原因
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//解释Arrays.binarySearch，如果搜索结果在数组中，刚返回它在数组中的索引，如果不在，刚返回第一个比它大的索引的负数-1
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//如果没弄明白，请自己想查看api
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int index = Arrays.binarySearch(mPositions, position);
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return index >= 0 ? index : -index - 2; //当index小于0时，返回-index-2，
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}
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}
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