问题描述

public Cursor set_datetime_next(Reminder r) {       
    String _newVal = "datetime('now', '+7 days')";
    String[] args = { new Integer(r.getID()).toString() };
    String query =
        "UPDATE " + DBConst.TABLE
      + " SET "   + DBConst.f_DATETIME_NEXT + "=" + _newVal
      + " WHERE " + DBConst.f_ID +"=?";
    Log.i(TAG, query);
    return db.rawQuery(query, args);
}

我也尝试过将 datetime('now', '+7 days') 作为绑定参数传递，这不起作用，因为 Android 文档 说:

I have also tried passing in datetime('now', '+7 days') as a bound parameter, that will not work, as the Android documentation says:

这些值将被绑定为字符串.

The values will be bound as Strings.

参考资料:

• http://developer.android.com/reference/android/数据库/sqlite/SQLiteDatabase.html
• http://www.sqlite.org/lang_datefunc.html

推荐答案

光标没有关闭.

public void set_datetime_next(Reminder r, String _newVal) {     
    String[] args = { new Integer(r.getID()).toString() };
    String query =
        "UPDATE " + DBConst.TABLE
      + " SET "   + DBConst.f_DATETIME_NEXT + "=" + _newVal
      + " WHERE " + DBConst.f_ID +"=?";
    Log.i(TAG, query);
    Cursor cu = db.rawQuery(query, args);
    cu.moveToFirst();
    cu.close();     
}

虽然这是有道理的，但真正让我感到困惑的是调用 moveToFirst() (或以某种方式使用"光标的其他函数)的要求.
如果没有同时调用 moveToFirst() 和 close()，则该行永远不会更新.close() 本身，在 rawQuery() 之后，什么也没做.

While that makes sense, what really puzzles me is the requirement of calling moveToFirst() (or some other function which would "work with" the cursor in some way).
Without the call to both moveToFirst() and close(), the row was never updated. close() by itself, after the rawQuery(), did nothing.

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