Displaying item info from list

I am attempting to develop an app to reward students with digital points that can be spent for prizes. I have a google sheet set up with all the information needed: first name, last name, id number, class period, and amount of points. Each student will carry a "debit" card that will have their id number in the form of a barcode on it.

I want to scan the barcode and have the app display the information and the option to add or subtract points from their "accounts" in the google sheet.

I have worked on this and have gotten different aspects to work. I have now confused myself so much from the research and different trials that I don't even know where I am.

I will attempt to add my pics. Please help if you can. Ask if this isn't clear enough. I will try to explain the best I can. So confused!!

Screen 1: Has scanner and text box and clock that filters listview. Want to select from list view to go to StudentInfo Screen

I get his error going from Screen1 to StudentInfo

ScanScreen: Has scanner and text box with the idea to go to studentinfo screen

StudentInfo Screen: Displays the information in a formatted way and has the ability to add/subtract points to a google sheet and updates

Based on your blocks it is clear that you ate not sending lists to next screen..

Makr sure what is present in global filtered list.

Also you are adding item into this list after clock timer. If so when do the clock timer triggered? Why it is missing in blocks? And why didnt you show us when did it goes off?

Hello Brian

Well, your code has confused me!

What you need to do now, first and foremost, is to draw a schematic of your process. Draw the Screens, draw the comms between them. Bullet-point list the tasks each screen has to accomplish.

For future reference, use App Inventor to capture screenshots:
Right-mouse in the Blocks work area and select "Download Blocks as image"

I would consider converting your Project to Virtual Screens.

When we define virtual screens, we use one 'real' App Inventor Screen (most often Screen1). Screen-sized Vertical Arrangements on it are displayed/hidden as required - they are the Virtual Screens. This is generally a better approach for multi-screen Apps, they share data without having to "pass" it between screens and it also reduces code duplication, making the App more efficient and the code easier to follow if you have to return to it at a later date.

So, instead of separate "houses", virtual screens are "rooms" of the same "house".

Thank you Chris! I will give this a shot after I have my process mapped out as you suggested. I will post a reply with questions as they come up. Thanks again.

Spicy, thanks for your reply as well. To be honest, I used the timer suggestion from a post on one of the help topics here and it works so I didn't really examine when it fires.


There is an old saying:

Don't count your chickens before they are hatched.

Don't format your data before it arrives.

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It's very good to learn from the Forum Topics. In this case though, you need a Procedure, not a Clock Timer.

Thank you for the response. I will definitely look into using a procedure. I am working on the virtual screens. I hope to be able to try them out soon.

Good advice. I hadn't really considered that in this case. :grinning:

hi! Can i ask for the ai on this? Thank you!

Hi. Are you wanting it to be able to see what can be done to "fix" it or are you wanting to just use it for yourself? I don't mind, either way, I will definitely share it with you. I will send it to you this evening once I get home from school.

I wanted to use it if its okay. I am trying to create a reward app too.Can you send it to my email?