In my android app the user has to login with a Named User from Portal for ArcGIS. When the user has logged in once, he shoudn't need to log in any more, when he reuses the app later. So I am looking for a best practise to store the login data somehow on the devise and read it later from the app to use it with the portal. So the user doesn't have to login again when he reuses the app.
Is there a recommended way for this approach?