package cn.sinata.xldutils.widget;

import android.widget.SectionIndexer;
import java.util.Arrays;

public class CustomSectionIndexer  implements SectionIndexer {
    private final String[] mSections;//
    private final int[] mPositions;
    private final int mCount;

    /**
     * @param sections
     * @param counts
     */
    public CustomSectionIndexer(String[] sections, int[] counts) {
        if (sections == null || counts == null) {
            throw new NullPointerException();
        }
        if (sections.length != counts.length) {
            throw new IllegalArgumentException(
                    "The sections and counts arrays must have the same length");
        }
        this.mSections = sections;
        mPositions = new int[counts.length];
        int position = 0;
        for (int i = 0; i < counts.length; i++) {
            if(mSections[i] == null) {
                mSections[i] = "";
            } else {
                mSections[i] = mSections[i].trim();
            }

            mPositions[i] = position;
            position += counts[i];
        }
        mCount = position;
    }

    @Override
    public Object[] getSections() {
        // TODO Auto-generated method stub
        return mSections;
    }

    @Override
    public int getPositionForSection(int section) {
        //change by lcq 2012-10-12 section > mSections.length以为>=
        if (section < 0 || section >= mSections.length) {
            return -1;
        }
        return mPositions[section];
    }

    @Override
    public int getSectionForPosition(int position) {
        if (position < 0 || position >= mCount) {
            return -1;
        }
        //注意这个方法的返回值，它就是index<0时，返回-index-2的原因
        //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
        //如果没弄明白，请自己想查看api
        int index = Arrays.binarySearch(mPositions, position);
        return index >= 0 ? index : -index - 2; //当index小于0时，返回-index-2，

    }

}