com.facebook.login.widget.LoginButton btn = new LoginButton(this); btn.performClick();
@Override public Completable loginWithFacebook(final Activity activity) { return Single.create((SingleOnSubscribe<AuthCredential>) e -> { LoginButton button = new LoginButton(activity); facebookCallbackManager = CallbackManager.Factory.create(); button.registerCallback(facebookCallbackManager, new FacebookCallback<LoginResult>() { @Override public void onSuccess(LoginResult loginResult) { e.onSuccess(FacebookAuthProvider.getCredential(loginResult.getAccessToken().getToken())); } @Override public void onCancel() { e.onError(null); } @Override public void onError(FacebookException error) { e.onError(error); } }); button.callOnClick(); }).flatMapCompletable(authCredential -> signInWithCredential(activity, authCredential)); }