Select item list error

MIT App Inventor Help
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1

Hi, I have a problem with the lists, I should save the indexes with a certain value so as to have as a result the value contained in those indexes, using logic I managed to get the result but app inventor signals me every time the error that see in the picture ... there are no empty lists or in any case lists with index lower than 1, how can I solve it? Sorry for the wrong english I used google translate.

blocks (8)
blocks (8)1010×871 85.4 KB

Cattura

2
  1. Call your procedure something other than "procedure"
  2. Use "if" condition statements instead of "while test" to avoid never ending loops and crashes
  3. Are you sure you want to do this:

image

better to do this:

image

Remove all elements from your procedure except the first and test, then add the next part and test, Which one causes the error?

3

It probably comes from the select list

blocks

This happens when the screen doesn't has a start value

4

Thanks for the reply, I did this and it didn't give me any errors

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blocks (9)1059×448 41.5 KB

after I added these blocks and the error returned .. there may be something wrong with these blocks, but I don't understand what
Can you give me some other advice? Thank you.

blocks (10)
blocks (10)814×966 96.2 KB

5

I assure you that I have passed the values from the previous screen.

6

You are calling the procedure in the middle of the gotValue event. Move everything below where you call the procedure into the procedure

7

Like this? or should I call the procedure under a gotvalue-like block?

blocks (11)

blocks (12)
blocks (12)1059×1120 115 KB

Doing so does not resolve the error.

8

You still have a "while test" to get rid of....

9

Thanks so much!!! :slight_smile: I hadn't noticed
The error no longer occurs, I will never use the while again
Thank you so much again :slight_smile:

10

music to my ears :+1:

1 Like
11

Looking at your blocks, I suspect you have not studied the CSV (Comma Separated Values) conversion blocks.

Look for them in the lists section.
There are 4 of them.

12

No, I didn't know it existed, could studying this thing help me in any way? I take all the data from the firebase and then manipulate it.
I used csv files for c programming.
A basic requirement for my project was to use a database for this I didn't use csv files.

13

It could reduce the amount of coding needed to swap between internal and external list representations.

Also see the text JOIN With Separator block.

14

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