SimpleAdapter需要一个_id领域 [英] SimpleAdapter needs an _id field

问题描述

我得到这个：

光标C = db.query（组织，NULL，NULL，NULL，NULL，NULL，NULL）;

这意味着我选择一表组织，但与此一并我需要这样的：

which means I choose a table "Org", but together with this I need to make this :

 Cursor c = db.rawQuery(" SELECT "+ id + " AS _id")

由于SimpleAdapter需要有一个 _id 字段不一定出于某种原因，否则将有一个错误崩溃。我如何结合成一个查询这2？

because SimpleAdapter need to have an _id field necessarily for some reason or it will crash with an error. How do I combine this 2 into one query?

推荐答案

有关您的语句：光标C = db.query（组织，NULL，NULL，NULL，NULL，NULL，NULL） ; 第二个参数是错误的，你shoukd提列名在其

For your statement : Cursor c = db.query("Org", null, null, null, null, null, null); the second parameter is wrong, you shoukd mention the column names in it.

public Cursor query (boolean distinct, String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy, String limit)

而对于，

Cursor c = db.rawQuery(" SELECT "+ id + " AS _id from Org"); 

意味着你选择 ID 并使用创建它的别名为到 _id ，而你选择这个 ID 从 单位表。
所以现在你就可以从该查询从列名 _id ，访问结果，并以访问结果使用：

means that you Select id and create an alias of it using AS into _id, and you are selecting this id from Org table. so now you will be able to access the result from this query from the column name _id, and in order to access the result use:

c.moveToFirst();    
while (c.moveToNext())
{
 System.out.println(c.getString(c.getColumnIndex("_id")); 
}

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