I'm new into SharePoint, i searched a lot for how to get Active Directory data into android using REST API, but i could not found any suitable solution up to that, for example i want to access logged user email id or user name into my autocomplete text view. any idea?
I don't think the Active Dirctory has rest API (you have one with Azure AD). But From what I understand you want to get the basic info about currently logged in user. Have a look at this answer should give you the right place to start. get current user info using jquery ,REST and csom
While you are using SharePoint Online so yes you can by using API Graph Azure Active Directory
In SharePoint Online, if you want to get all the users from the Azure AD, we can use Graph API to achieve it.
If you use SharePoint on-premise and use AD, we can create a custom REST API and use server code to get the AD users, then consume the REST API in your Android App.
Or we can synchronize the AD users to a SharePoint lists, then using the OOTB REST API to achieve it.
The following articles for your reference.