getColumnIndex(_ID) returns 零，getlong(getColumnIndex(_ID)) = 正确值

Question

所以当我使用 int location = cursor.getColumnIndex(_ID) 它总是 returns 零，尽管 long locationId = cursor.getlong(getColumnIndex(_ID) returns 7. 为什么我得到不同的值？

    if (locationCursor.moveToFirst()) {
        //This is where the problem is happening
        locationId = locationCursor.getLong(locationCursor.getColumnIndex(WeatherContract.LocationEntry._ID));
        //=7
        int location = locationCursor.getColumnIndex(WeatherContract.LocationEntry._ID);
        // = 0

Answer 1

cursor.getColumnIndex(_ID) returns 0 即_ID列在数据库中的索引（位置）table

cursor.getLong(cursor.getColumnIndex(_ID)) returns 7 是当前游标所在（行）的数据库table列_ID中存储的值.