Managing a list of lists of checkboxes

[John Bradford]

Hi all, getting an error I don't quite understand enough to figure out the resolution.

I'm building a multi-choice questionnaire. There will be some questions (in rows, currently 6 per page) with 5 options per question (in columns). I'm using checkboxes to select options for each row. I started out hard coding for each checkbox which worked, but was very messy, so decided to try and do everything in a procedure loop that could be called by each checkbox passing the row / column reference.

I create a list of lists for the checkbox components, each row is a list of the checkboxes in columns

Then each checkbox gets a simple call when it's state changes

What should then happen is that the code looks up the relevant checkbox component from the list-of-lists, and proceeds based on whether or not it is checked

Not sure if that image is readable, so the first 'line' reads:

If Checkbox.Checked of component (select list item from list "globalCheckBoxComponents", index (select list item from list (get row, index (get column))))

And it throws the following error:

Which I assume means I can't use "Select List Item" Index to reference a list within a list. but then I'm not sure how to reference them?

I also tried loading the list of checkboxes into a local list so I was only navigating one layer deep:

And yeah, that didn't work either - but gave a *much* bigger error. So really didn't work!

Any thoughts?

[Taifun]

use 2 nested select list item blocks to get the value like this

select list item select list item get global checkboxComponents

                                                get row

                        get column

• How to work with Lists by Saj
• How to work with Lists and Lists of lists (pdf) by appinventor.org

you might want to use Do it to debug your blocks, see tip 4 here https://puravidaapps.com/learn.php

Taifun

---

Trying to push the limits of App Inventor! Snippets, Tutorials and Extensions from Pura Vida Apps by Taifun. 

[Abraham Getzler]

This is similar to a radio button, which is a group of buttons,

but you have added an extra dimension of a lot of them.

See https://groups.google.com/d/msg/mitappinventortest/8uN5KbNNPlA/Uxnbe3JbCAAJ

Also see https://docs.google.com/document/d/1RbPhI6cnHz3pRfqpEOVtRoMdkQlEA3Qm5BtuYq4bbGY/edit?usp=sharing

to avoid burying yourself in components.

abg

[SteveJG]

Here is a link to making 'Radio Buttons' from CheckBoxes (which ABG believes is similar to your coding problem.)  https://groups.google.com/forum/#!searchin/mitappinventortest/radio/mitappinventortest/i4MJIXFIWoA/5ac6_9AVz5EJ   If only one answer is correct in your 'quiz' then you could add two checkboxes to this example for each row and use similar coding.  This will prevent anyone from checking more than one box in a row.  It may not solve other issues.

Regards,

Steve

[John Bradford]

Thanks for the comments.

Tried re-organising @Taifun it produced a different error, so might be making progress....

Steve / ABG - ensuring only one check box is selected isn't the issue. It's being able to select a checkbox from a list of lists. It seems to be something to do with passing arguments through the select list item. Will take a look at the examples and see if that works.

thanks

[Taifun]

Taifun

[John Bradford]

Doh! And solution found!

Many thanks Taifun.

The final error was that when I cycled through the "row" list of checkboxes, I was actually returning the component, not it's column number. So introduced a local index "localBox" and everything worked perfectly.

Many thanks!