Check if user exist in firebase

[khlifat_wael]

hello everyone
can i know how to check when i make registration user - if a user exist in firebase or no and prevent to overwrite!!! the user is 500

[Ria_Das]

Call tag Users, when got data if username exists in list show notification if not add data to firebase

[khlifat_wael]

Can you put sample

[TIMAI2]

Something like this:

It looks like you need to do some learning and research about using AppInventor and Firebase:

for AppInventor:

A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook App Inventor 2 Book: Create Your Own Android Apps ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here Course In A Box and the aia files for the projects in the book are here: App Inventor 2 Book: Create Your Own Android Apps
How to do a lot of basic things with App Inventor are described here: How do you...? .

Also do the tutorials Our Tutorials! to learn the basics of App Inventor, then try something and follow the Top 5 Tips: How to learn App Inventor

Taifun

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

and for Firebase:

FAQ Section: Firebase

Introductory FireBase Pending Failure Warning - JIS Brief Intro to Cloud Data and the FireBase Component - HAL FireBase component help The firebase console URL is https://console.firebase.google.com/ - @ABG 12/2025 Tutorials Atomic queue and delete - @TimAI2 Simple bulletin board - @TIMAI2 Firebase Chat sample - Amerikashi Firebase bus route tutorial - Romin Irani Firebase Spanish tutorial - kio4 Firebase WhatsAppInventorMIT chat project - Montes FireBase DataChanged Detection from I…

also

https://ai2.metricrat.co.uk/guides