Facebook SDK 4 for Android - how to log out programmatically

You can use LoginManager.getInstance().logOut();, even if you use LoginButton because

This UI element wraps functionality available in the LoginManager.

EDIT: Just to mention that this works for Facebook SDK v4. I don't know if they will change it in the future.

@as batoutofhell mention, don't forget to put FacebookSdk.sdkInitialize(getApplicationContext()); to initialize the facebook sdk. Please see here for the details.

SDK4, if you want to completely de-couple, make sure you also remove the app from the user's facebook account. This method disconnects the user completely:

public void disconnectFromFacebook() {

    if (AccessToken.getCurrentAccessToken() == null) {
        return; // already logged out
    }

    new GraphRequest(AccessToken.getCurrentAccessToken(), "/me/permissions/", null, HttpMethod.DELETE, new GraphRequest
            .Callback() {
        @Override
        public void onCompleted(GraphResponse graphResponse) {

            LoginManager.getInstance().logOut();

        }
    }).executeAsync();
}