光标索引出界异常的 [英] Cursor Index Out of Bounds Exception

问题描述

在试图对我的数据库执行查询，我得到这个例外。但是，文档指出该方法 SQLiteDatabase.query（...）的回报，一个Cursor对象，它是定位在第一项之前，这是我除preT意味着光标在返回的行的开始。如果我添加了 Cursor.moveToFirst（）光标访问数据之前，我没有得到任何的异常。到底是怎么回事？我是否需要试图让数据之前，总是称之为moveToFirst？该文件说，这种方法，将光标移动到第一行。

 光标C = db.query（TABLENAME，NULL，NULL，NULL，NULL，NULL，NULL）;
Log.d（TAG，+ c.getInt（c.getColumnIndex（_ ID）））;
 

解决方案

查询后，您需要调用下一个（）或 moveToFirst（）。光标懒加载，调用光标被加载到内存这些方法之后。您可以决定什么时候做。

In attempting to execute a query on my database, I get this exception. However, the documentation states that the method SQLiteDatabase.query(...) returns, "A Cursor object, which is positioned before the first entry," which I interpret to mean that the Cursor is at the start of the rows returned. If I add the Cursor.moveToFirst() before accessing data in the Cursor, I get no exception. What is going on? Do I need to always call "moveToFirst" before trying to get data? The documentation says this method, "moves the cursor to the first row."

Cursor c = db.query(TABLENAME, null, null, null, null, null, null);
Log.d("TAG",""+c.getInt(c.getColumnIndex("_id")));

解决方案

After query you need to call next() or moveToFirst(). Cursors are lazy loaded, after calling these methods cursor is loaded into memory. You can decide when to do it.

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