由网友(奶油味拥抱)分享简介：我执行下面的方法没有成功东阳的selectArgs的是不正确的（至少这是我相信。I'm executing the following method with no success beacause of the selectArgs being incorrect (at least this is what I...

我执行下面的方法没有成功东阳的selectArgs的是不正确的（至少这是我相信。

I'm executing the following method with no success beacause of the selectArgs being incorrect (at least this is what I believe.

的findAll：

public Collection<Object> findAllByCodigoSetorOrderByStatusWhereDataAgendamentoIsNull(Integer vendedor) {
    Collection<Object> objects = null;
    String selection = Object.FIELDS[20] + "=?" + " OR " + Object.FIELDS[20] + "=?" + " OR " + Object.FIELDS[20] + "=?" + " AND " + Object.FIELDS[6] + "=?";
    String[] selectionArgs = new String[] { "''", "'null'", "NULL", String.valueOf(vendedor) };
    Collection<ContentValues> results = findAllObjects(Object.TABLE_NAME, selection, selectionArgs, Object.FIELDS, null, null, Object.FIELDS[4]);
    objects = new ArrayList<Object>();
    for (ContentValues result : results) {
        objects.add(new Object(result));
    }
    return objects;
}

findAllObjects：

protected Collection<ContentValues> findAllObjects(String table, String selection, String[] selectionArgs, String[] columns, String groupBy, String having, String orderBy) {
        Cursor cursor = null;
        ContentValues contentValue = null;
        Collection<ContentValues> contentValues = null;
        try {
            db = openRead(this.helper);
            if (db != null) {
                cursor = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
                contentValues = new ArrayList<ContentValues>();
                for (int i = 0; i < cursor.getCount(); i++) {
                    cursor.moveToPosition(i);
                    contentValue = new ContentValues();
                    for (int c = 0; c < cursor.getColumnCount(); c++) {
                        contentValue.put(cursor.getColumnName(c), cursor.getString(c));
                    }
                    contentValues.add(contentValue);
                    cursor.moveToNext();
                }
            }
            return contentValues;
        } finally {
            close(db);
        }
    }

我怎样才能正确地选择和列比较 - 空，空，并使用db.query''

How can I correctly select and compare a column to - null, 'null' and '' using the db.query?

推荐答案

Android的数据库API不允许通过 NULL 值作为参数;它只允许琴弦。 （这是一个可怕的设计缺陷。更糟糕的是，SQLiteStatement 确实的允许所有类型的参数，但仅限于返回一个值的查询工作。）

Android's database API does not allow to pass NULL values as parameters; it allows only strings. (This is a horrible design bug. Even worse, SQLiteStatement does allow all types for parameters, but works only for queries that return a single value.)

您没有选择，而是要改变查询字符串等等IS NULL 。

You have no choice but to change the query string to blah IS NULL.