Android 利用cursor来进行排序

       主要思路是:override move系列的方法,让cursor以自己想要的顺序来移动,从而达到对cursor排序的目的。比如数组A0里有 4(0),3(1),1(2),2(3),括号内为位置,排序后用数据记录A1:1(2),2(3),3(1),4(0)。要访问第一个元素,则访问A1[0]得到1(2),根据(2)找到在A0中的实际位置2,即1(2)。参考了下系统的CursorWrapper和AbstractCursor代码实现,另外有时间可以顺带了解下MatrixCursor。

package com.xx.test;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import android.database.Cursor;
import android.database.CursorWrapper;
import com.xx.test.SortCursor.SortEntry;
public class SortCursor extends CursorWrapper implements Comparator<SortEntry>{

public SortCursor(Cursor cursor) {
super(cursor);
}

Cursor mCursor;
ArrayList<SortEntry> sortList = new ArrayList<SortEntry>();
int mPos = 0;
public static class SortEntry {
public String key;
public int order;
}

public int compare(SortEntry entry1, SortEntry entry2) {
return entry1.key.compareTo(entry2.key);
}

public SortCursor(Cursor cursor, String columnName) {
super(cursor);

mCursor = cursor;
if (mCursor != null && mCursor.getCount() > 0) {
int i = 0;
int column = cursor.getColumnIndexOrThrow(columnName);
for (mCursor.moveToFirst(); !mCursor.isAfterLast(); mCursor.moveToNext(), i++) {
SortEntry sortKey = new SortEntry();
sortKey.key = cursor.getString(column);
sortKey.order = i;
sortList.add(sortKey);
}
}
Collections.sort(sortList, this);
}
public boolean moveToPosition(int position) {
if (position >= 0 && position < sortList.size()) {
mPos = position;
int order = sortList.get(position).order;
return mCursor.moveToPosition(order);
}
if (position < 0) {
mPos = -1;
}
if (position >= sortList.size()) {
mPos = sortList.size();
}
return mCursor.moveToPosition(position);
}
public boolean moveToFirst() {
return moveToPosition(0);
}
public boolean moveToLast() {
return moveToPosition(getCount() - 1);
}
public boolean moveToNext() {
return moveToPosition(mPos + 1);
}
public boolean moveToPrevious() {
return moveToPosition(mPos - 1);
}
public boolean move(int offset) {
return moveToPosition(mPos + offset);
}
public int getPosition() {
return mPos;
}
}