Question

我正在运行以下查询：

String q = "select " + MySQLiteHelper.COLUMN_ID + ", "
        + MySQLiteHelper.COLUMN_TASK + ", "
        + MySQLiteHelper.COLUMN_PARENT + ", count(*) from "
        + MySQLiteHelper.TABLE_TASKS + " where "
        + MySQLiteHelper.COLUMN_ID + " = " + insertId + " group by "
        + MySQLiteHelper.COLUMN_ID + ", " + MySQLiteHelper.COLUMN_TASK
        + ", " + MySQLiteHelper.COLUMN_PARENT;
Cursor cursor = database.rawQuery(q, null);

当我像这样读取检索到的数据时：

task.setId(cursor.getLong(0));
task.setTask(cursor.getString(1));
task.setParent(cursor.getLong(2));
task.setChildren(cursor.getInt(3));

我收到以下错误：

03-15 22:15:06.078: E/AndroidRuntime(31426):
    java.lang.IllegalStateException:
    Couldn't read row 0, col 3 from CursorWindow.
    Make sure the Cursor is initialized correctly before accessing data from it.

如果我删除该行

task.setChildren(cursor.getInt(3));

工作正常。

有谁能告诉我这里有什么问题以及如何解决？

Answer 1

尝试替换此行

+ MySQLiteHelper.COLUMN_PARENT + ", count(*) from "

通过

+ MySQLiteHelper.COLUMN_PARENT + ", count(*) as total from "

修改：还可以尝试替换

task.setChildren(cursor.getInt(3));

通过

task.setChildren((int)cursor.getLong(3));

或可能是

task.setChildren(Integer.parseInt(cursor.getString(3)));

Answer 2

您正在直接尝试从光标访问3列，但您的第三列是计数，并且您未指定该列的别名，这就是您收到此错误的原因。只需尝试输入列名的别名，然后尝试访问它，如下所示：

替换此行

   + MySQLiteHelper.COLUMN_PARENT + ", count(*) from "

通过

    + MySQLiteHelper.COLUMN_PARENT + ", count(*) as total from "

Android SQLite聚合函数错误

2 个答案: