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。

 

import java.text.Collator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import android.database.Cursor;
import android.database.CursorWrapper;

public class SortCursor extends CursorWrapper{
Cursor mCursor;
ArrayList sortList = new ArrayList();
int mPos = 0;


public class SortEntry {
public String key;
public int order;
}

//直接初始化,加快比较速度,在G3上从3s->0.2s
@SuppressWarnings("rawtypes")
private Comparator cmp = Collator.getInstance(java.util.Locale.CHINA);
@SuppressWarnings("unchecked")
public Comparator comparator = new Comparator(){
@Override
public int compare(SortEntry entry1, SortEntry entry2) {
return cmp.compare(entry1.key, entry2.key);
}
};

public SortCursor(Cursor cursor,String columnName) {

super(cursor);
MusicLog.i("MediaScanner", "start-----------");
// TODO Auto-generated constructor stub
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);
}

}

MusicLog.i("MediaScanner", "start1-----------");
//排序
Collections.sort(sortList,comparator);
MusicLog.i("MediaScanner", "start2-----------");
}
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;
}

}