I need to report in my app that the entered value is incorrect

I am developing a factorial calculator, my teacher asked that if anyone enters any incorrect data, the application immediately responds that said operation is incorrect. I need help, I am new to this. ThanksFactorial.aia (2.1 KB)

Hello Adrian

Use the Notifier Component to pop-up a message to the User.

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Welcome to the community. You could use an if ... then ... else ...statement to check textbox's value if contains any incorrect data. If contains then call a notifier to inform users that invalid data was entered else proceed with calculation

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I have a solution for this, but, I'll need some information. Could you please export the .aia file of your program and post it here?

Steps to export your project's .aia:
Step 1: Open and sign onto App Inventor.
Step 2: Open the app whose .aia you want to export.
Step 3: Click on the My Projects drop-down menu located near the top of the page, and click on "export selected project (.aia) to my computer" in it.

You can use the upload function on this community (picture below for reference) to upload a file onto it:

Here is your first test:

Factorial calculations work best with numbers equal to or greater than 1, so that's some more tests to add.

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Hello, factorial is of a non-negative integer, so you need to test for Integer and its Non Negativity as well.

You can also use label to prompt user regarding input errors, as