Check existing user before Facebook/Twitter signup Parse Android SDK

Question

I'm working with Parse Android SDK and I have two signup options in my signup activity. Signup by twitter and Signup by facebook.

Here's the problem: If I signup using facebook and then logout and then again signup using twitter, instead of linking the new twitter parse user to the old facebook parse user, it creates a new user even though the email used in both facebook and twitter were same.

What I want to achieve is to check if the user with the same email exists if not then create new user and if he does exist then link the signup method (facebook or twitter) with the existing parse user.

Any help would be greatly appreciated. Thanks

private void loginWithTwitter() {
    signUpProgressDialog.show();
    ParseTwitterUtils.logIn(this, new LogInCallback() {
        @Override
        public void done(ParseUser user, ParseException e) {
            signUpProgressDialog.dismiss();
            if(e==null) {
                if (user == null) {
                    Log.d(TAG, "Uh oh. The user cancelled the Twitter login.");
                } else if (user.isNew()) {
                    Log.d(TAG, "User signed up and logged in through Twitter!");
                    startAppropriateActivity("TWITTER_NEW");
                } else {
                    Log.d(TAG, "User logged in through Twitter!");
                    startAppropriateActivity("TWITTER_OLD");
                }
            }else Log.d(TAG,"Twitter Parse Error");
        }
    });
}

private void loginWithFacebook() {
    signUpProgressDialog.show();
    List<String> permissions = Arrays.asList("public_profile", "email");
    ParseFacebookUtils.logIn(permissions, this, new LogInCallback() {
        @Override
        public void done(ParseUser user, ParseException e) {
            signUpProgressDialog.dismiss();
            if(e==null) {
                if (user == null) {
                    Log.d(TAG, "Uh oh. The user cancelled the Facebook login.");
                } else if (user.isNew()) {
                    Log.d(TAG, "User signed up and logged in through Facebook!");
                    startAppropriateActivity("FACEBOOK_NEW");
                } else {
                    Log.d(TAG, "User logged in through Facebook!");
                    startAppropriateActivity("FACEBOOK_OLD");
                }
            }else Log.d(TAG,"Facebook Parse Error");
        }
    });
}

Answer 1

You can set user's email as a content of username field in the ParseUser object. So next time user will try to signup with same username you will receive ParseException with code 202 - "User with these username and password already registered" and in that case you can call login() method. But in this case password should stay the same between two sessions.