What does "Delete Item from list" do?

[roty]

Hello,

I do not quite understand what "Delete item from list" does.
Provided , I have list with 30 item, what happens with the flowing 29 items?
Is Item 2 before delete than item 1 after delete and the number of entries is 29 ?

Can anybody advice , please?

[Taifun]

@roty

Is Item 2 before delete than item 1 after delete and the number of entries is 29 ?

Yes; if you delete the first item in a list; then the item, which was at index 2 is now at index 1 and the length of the list is now 29

Imagnity.com List Tutorial, Mirrored - @Saj

(copied from imagnity.com, courtesy of @Saj) List Blocks On App Inventor by Sajal Dutta | app-inventor, tutorials | 102 comments List is a necessity in almost every app regardless of what programming language you use. This is the easiest way to create and manipulate a set of values/items/elements in an ordered fashion. Please go over the reference before we start. In this tutorial, we will learn how to create a list, add new items to a list, display list items, replace an item in the list, re…

Taifun

[SteveJG]

@roty

"Delete item from list"

Are you asking what happens if you use the remove list item block (highlighted in yellow)?

All the List Blocks you can use for LISTS are in the MIT App Inventor List Blocks documentation.

Why not make yourself a simple Project creating a List of 5 or so items, then use the remove list item block on the third index item.. What happens? When you DELETE an Item, you must specify the index of the item you want to delete.

[roty]

Thanks for your answers.

I already use list-blocks, but the reason I'm asking is , the result is not as expected.

@SteveJG The documentation you mentioned is not sufficient , at least for me.

I would like to display a chart from list. If the list has reached the maximum number of
entries, I would like to shift the chart to the left. For that I use "remove list item " block
for the oldest item, enter the newest value to top the list and try to display the chart.
Until the list is not full, everything is working correctly, but shift chart to left doesn't work.
The chart remains frozen.
So I thought I misunderstand anything.

[SteveJG]

@roty

"delete item from list" block

Unfortunately there is not a native "delete item from list" Block roty. Are you using an extension to delete?

Perhaps you should share an image of your Blocks and show how you are attempting to:

@roty

I would like to display a chart from list. If the list has reached the maximum number of
entries, I would like to shift the chart to the left. For that I use "remove list item " block
for the oldest item, enter the newest value to top the list and try to display the chart.
Until the list is not full, everything is working correctly, but shift chart to left doesn't work

[ABG]

Search the Web for "linked lists".

That's what AI2 uses

[roty]

Sri, I mean standard AI2 list block

[quote="roty, post:4, topic:152427"]
"remove list item " block
[/quote] just not in English

[ABG]

Need Help with app (graphing/charting Charts component)

Please also post your sketch code. You are expecting exactly 3 bytes of data, and it's unusual for numbers to be encoded like that. You need to test the length of list bytevalues, to insure it has at least 3 items in it, before trying to access items in that list. Also, list indexes do not need conversion, just use 1,2,3,... [image] You can get more reliable conversion decision making based on the incoming characteristicUUID, since you went to the trouble of making 3 of them, right? [imag…

See this Drunkards Walk sample.

[roty]

Thanks a lot for all your help!

The Drunkards Walk sample example is exactly what I would like to do. Just much better realized!

Now it works as expected and I can continue.