QGIS Custom Widgets – Sorting Drop-Down Lists in Value Relation Widget

Question

I have some attributes in my data and want to enable the user to pick values from drop-down lists. The values of the drop-down list change depending on the chosen value of the previous field(s). The values for the drop-down come from different domain tables.

The task I can accomplish perfectly with Value Relation Widget. However, it works only when I choose the same attribute "Key column" and Value Column. When I do that, I can only sort the drop-down alphabetically. In my domain table, I have a column for sorting and I would like to use that. When I choose that column then the hierarchy won't work anymore.

So it works if it is set like this

Here is how the drop-down works but alphabetically ordered

My attempt to order them differently

As you can see here

the values for L_PZART_KTG is sorted by SORT attribute, but the hierarchy won't work anymore. Nothing will be listed for L_GZGRP_KTG.

Answer 1

Due to the fact that I am poorly versed in German - I created a separate data set in English, which should be understandable to all readers of the site.

In order to sort the data in the QGIS drop-down list according to a manually defined order, you need to have the following fields in the tables.

Table 1:

1. table1_sort - manual sorting of rows.
2. table1_type - groups.

Table 2:

1. table2_sort - manual sorting of rows.
2. table2_type - groups.
3. table2_objects - objects.
4. table2_sort - The field that contains the same values as the table1_sort field.

New data will be entered in Table 3. It should contain the following fields:

1. types - groups.
2. objects - objects.

Now go to Table 3 field paramaters and set the Widget type to Value Relation.

Now select the types field and set the following parameters for it:

1. Layer -> Table 1
2. Key column -> table1_sort
3. Value column -> table1_type

Now select the objects field and set the following parameters for it:

1. Layer -> Table 2
2. Key column -> table2_sort
3. Value column -> table2_objects
4. Filter expression -> current_value('types') = "table1_sort"

Now you may try to enter your data with the Drop-down list (with manual sorting):

<== (click to watch)