因为对于cursor流不太熟悉，特别是在数据中查询一部分属性，而在网上也没找到相应的资料，因此我花时间研究了一下。以下是研究成果:

	public void getChatMsg(String friendName){
		Msg msg;
		String sql = "select a.msg,a.username,a.sendTime,a.inOrOut from(select * from chatRecord" +
				" where whosRecord = ? and friend = ? order by _id desc LIMIT " +SHOW_MSG_COUNT+")a order by a._id";
		Cursor cursor = db.rawQuery(sql,new String[]{XmppApplication.user,friendName});
		while(cursor.moveToNext()){
			msg = new Msg(cursor.getString(0),cursor.getString(1),cursor.getString(2),cursor.getString(3));
			Log.i(TAG,"cursor.getString(0)="+cursor.getString(0));
			//设置是和谁的聊天记录
			OneFridenMessages oneFridenMessages = XmppApplication.AllFriendsMessageMapData
					.get(friendName);
			if (oneFridenMessages == null) {
				oneFridenMessages = new OneFridenMessages();
				XmppApplication.AllFriendsMessageMapData.put(friendName,oneFridenMessages);
			}
			oneFridenMessages.MessageList.add(msg);
			msg = null;
		}
		cursor.close();
	}

public void getChatMsg(String friendName){
		Msg msg;
		String sql = "select a.username,a.msg,oneFridenMessages);
			}
			oneFridenMessages.MessageList.add(msg);
			msg = null;
		}
		cursor.close();
	}

当然cursor还有其他使用方法，但在本项目中中没用到，所以就不在此叙述了。