MySectionIndexer.java

package com.demo.sectionlistview;

import java.util.Arrays;

import android.widget.SectionIndexer;

/**
 * Section�ֶ�����
 * 
 * @author Liang
 * 
 */
public class MySectionIndexer implements SectionIndexer {
	private final String[] mSections;// �ֶ��ַ�����
	private final int[] mPositions;// �ֶ�λ������ֵ����
	private final int mCount;// ����������

	/**
	 * @param sections
	 * @param counts
	 */
	public MySectionIndexer(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() {
		return mSections;
	}

	/**
	 * ����ij�λ�ȡλ��
	 */
	@Override
	public int getPositionForSection(int section) {
		// change by lcq 2012-10-12 section >mSections.length��Ϊ>=
		if (section < 0 || section >= mSections.length) {
			return -1;
		}
		System.out.println("lcq:section:" + section);
		return mPositions[section];
	}

	/**
	 * �ṩ�öε������ַ���
	 */
	@Override
	public int getSectionForPosition(int position) {
		if (position < 0 || position >= mCount) {
			return -1;
		}
		// ע����������ķ���ֵ��������index<0ʱ������-index-2��ԭ��
		// ����Arrays.binarySearch�������������������У��շ������������е�������������ڣ��շ��ص�һ��������������ĸ���-1
		// ���ûŪ���ף����Լ���鿴api
		int index = Arrays.binarySearch(mPositions, position);
		return index >= 0 ? index : -index - 2; // ��indexС��0ʱ������-index-2��

	}

}