Index 3 requested, with a size of 3

最新推荐文章于 2022-10-17 21:40:22 发布

原创最新推荐文章于 2022-10-17 21:40:22 发布 · 1.2k 阅读

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#Android #SQLite #Cursor

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本文解析了在使用Cursor进行数据操作时常见的Index3requested错误，并详细解释了Cursor移动方法的工作原理。文章通过对比move(i)与moveToNext()的用法，指导开发者如何正确遍历结果集，避免因误解move方法而导致的程序错误。

使用Cursor时出现了 Index 3 requested, with a size of 3 的报错，当时使用的写法如下：

            if (c.moveToFirst()) {
                for (int i = 0; i < c.getCount(); i++) {
                    c.move(i);
                    list.add(c.getString(2));
                }
            }

其实文档里面有说明：

/**
     * Move the cursor by a relative amount, forward or backward, from the
     * current position. Positive offsets move forwards, negative offsets move
     * backwards. If the final position is outside of the bounds of the result
     * set then the resultant position will be pinned to -1 or count() depending
     * on whether the value is off the front or end of the set, respectively.
     *
     * <p>This method will return true if the requested destination was
     * reachable, otherwise, it returns false. For example, if the cursor is at
     * currently on the second entry in the result set and move(-5) is called,
     * the position will be pinned at -1, and false will be returned.
     *
     * @param offset the offset to be applied from the current position.
     * @return whether the requested move fully succeeded.
     */
    boolean move(int offset);

move(i)这个方法并不是移动到第i行，而是基于当前位置移动i行，如果只是遍历结果集，建议使用下面的语句：

 while(c.moveToNext()){
    list.add(c.getString(2));
 }