I have a problem with facebook user login in my android application. I want users use their facebook account to login my system but when I click login button facebook native
iOS and Android use something called Single Sign-on (SSO), which means anyone attempting to use Facebook in a 3rd Party app will launch the Facebook App for easier login. If the user has Facebook App installed, it will always launch the app for login - there is no way around it.
It's actually there for make it easier for the user. The user would usually be logged into the App already so using a 3rd Party FB App would only take a single touch / tap to authorise and use. You will find that user's without the FB app will see the web-based login page.