How to add whatsapp like options to contact whenever the is a new contact added to Contacts

Question

I develop an app which needs to do 2 things:

• Create a user account (like WhatsApp).
• Whenever there is a new contact entry, if the contact is using my app, then immediately in the Contacts application show options "call" or "message" in the contact detail page.

Example

Answer 1

You need to create a SyncAdapter, this is basically a service that is able to sync contacts to/from a server, like Google does for Google Contacts, you can set it to be notified when a new contact is added, and have your SyncAdapter add the needed info to the contact so it'll show links to your app.

If you go to your phone settings > accounts, you can see Whatsapp and Google's SyncAdapters there, where you can turn them off/on.

To create a sync adapter, you can follow the official docs, or this great tutorial.