使用游标的内部连接生成另一个Cursor对象 [英] Inner join with Cursors resulting another Cursor object

问题描述

其实我有2 Cursor 一个是SQLite游标，另一个来自 ContentProvider 复杂的SQLite查询 - 但我没有访问它。

两个游标都有相同的唯一 _ID 字段。在纯SQL中，使用这些id字段很容易加入它们，但是在我的情况下不行，因为第二个游标不是SQLite查询。

我需要生成结果加入 Cursor 。 CursorJoiner 或 MergeCursor 都不能帮助我。

选项＃1：编写自己的实现 Cursor / code> - 也许扩展 AbstractCursor - 执行连接。我在已停用的图书的旧版本中显示了一些古代码参见第186-190页）。

选项＃2：创建代表加入的 MatrixCursor >

In fact I have 2 Cursors one is SQLite cursor, another one comes from ContentProvider - beneath it lies complicated SQLite query - but I don't have access to it.

Both cursors has the same unique _ID field. In a pure SQL it would be really easy to join them using those id field, but not in my case, since 2nd Cursor is not SQLite query.

I need to produce resulting joined Cursor. Neither CursorJoiner nor MergeCursor doesn't help me.

Any ideas, clues, hints?

解决方案

Option #1: Write your own implementation of Cursor -- perhaps extending AbstractCursor -- that does the join. I have some ancient code in an obsolete version of a discontinued book that demonstrates this (see pages 186-190).

Option #2: Create a MatrixCursor that represents the join.

这篇关于使用游标的内部连接生成另一个Cursor对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！